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Effect of the Concentration and the Type of Dispersant on the Synthesis of Copper Oxide Nanoparticles and Their Potential Antimicrobial Applications
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  • Maribel Guzman*
    Maribel Guzman
    Engineering Department, Pontifical Catholic University of Peru, Av. Universitaria 1801, Lima 32, Peru
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0002-7954-7679
  • Mariella Arcos
    Mariella Arcos
    Sciences Department, Pontifical Catholic University of Peru, Av. Universitaria 1801, Lima 32, Peru
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  • Jean Dille
    Jean Dille
    4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
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  • Céline Rousse
    Céline Rousse
    LISM, EA 4695, UFR Sciences Exactes et Naturelles, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims cedex 2, France
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  • Stéphane Godet
    Stéphane Godet
    4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
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  • Loïc Malet
    Loïc Malet
    4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
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ACS Omega

Cite this: ACS Omega 2021, 6, 29, 18576–18590
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https://doi.org/10.1021/acsomega.1c00818
Published July 18, 2021

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Abstract

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The bactericidal properties of copper oxide nanoparticles have growing interest due to potential application in the medical area. The present research investigates the influence of sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) on the production of copper oxide nanoparticles prepared from copper sulfate (CuSO4) and sodium borohydride (NaBH4) solutions. Different analytical techniques were used to determine the crystal nature, mean size diameter, and surface morphology of the copper oxide nanoparticles. The X-ray diffraction (XRD) patterns showed formation of nanoparticles of cuprite (Cu2O) and tenorite (CuO) when PVP and SDS were added at the beginning of the reaction. In fact, when the Cu/PVP ratio was 1.62, Cu2O nanoparticles were obtained. In addition, nanoparticles of CuO were synthesized when the Cu/PVP ratios were 0.54 and 0.81. On the other hand, a mixture of copper oxides (CuO and Cu2O) and cuprite (Cu2O) was obtained when PVP (Cu/PVP = 0.81 and 1.62) and SDS (Cu/SDS = 0.90) were added 30 min after the beginning of the reaction. Transmission electron microscopy (TEM) images show agglomerated nanoparticles with a size distribution ranging from 2 to 60 nm, while individual particles have sizes between 4.1 ± 1.9 and 41.6 ± 12.8 nm. The Kirby–Bauer method for the determination of antibacterial activity shows that small CuO (4.1 ± 1.9 nm) and Cu2O (8.5 ± 5.3 nm) nanoparticles inhibit the growth of Escherichia coli, Staphylococcus aureusMRSA, S. aureus and Pseudomonas aeruginosa bacteria. The antibacterial test of cotton fabric impregnated with nanoparticles shows positive results. The determination of the optimal ratio of copper oxide nanoparticles per cm2 of fabric that are able to exhibit a good antibacterial activity is ongoing.

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Introduction

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Cuprous and cupric oxide have been investigated for decades due to their unique semiconductor and optical properties. (1) However, the study of antibacterial properties of copper oxide to develop new pharmaceutical products has gained great interest in the last few years. (2,3) In fact, cotton fibers containing copper oxide nanoparticles could be used as raw material to fabricate textiles with medical applications, such as wound dressing, protective suits, medical clothing for operation theatre or hospital areas, and others. (4)
There are several routes to obtain copper oxide nanoparticles with different shapes and sizes. (5) Some of the synthesis methods described in the literature are thermal decomposition, (6,7) calcination, (8) pyrolysis, (9) sonochemistry, (10) electrochemistry, (11−13) colloid formation, (14) microwave irradiation, (15) precipitation, (16−18) reduction, (4,19−22) reverse micelles, (23) sol–gel method, (24) self-assembled methods, (25,26) and biosynthesis using plant extracts. (27) In addition to these methods, the oxidation–reduction technique that involves a reduction of copper ions in aqueous medium using a reducing agent has been well developed. (17) Furthermore, the precipitation process is especially more attractive due to its simplicity. On the other hand, surfactants play an important role in synthesizing nanoparticles. They control the size and shape of particles and prevent their agglomeration. Dispersant molecules are likely to be adsorbed on specific crystal planes and thus promote an anisotropic growth of the crystal structure. Moreover, the presence of surfactant reduces the interfacial energy between nanoparticles and the solution, which facilitates the nucleation process and allows for its easier growth. (19) Depending on the surfactant used, it is possible to control the shape of nanoparticles by the selective binding of ligands to certain crystal facets. When ligands are used in a colloidal synthesis of nanoparticles, the interaction between them allows for self-assembly of nanoparticles in an ordered structure. (28) Many authors have reported the use of various dispersants during the synthesis of copper oxide nanoparticles, such as cetyl trimethyl ammonium bromide (CTAB), (29,30) ethylene glycol, (31) polyacrylamide (PAM), (26) poly(ethylene glycol) (PEG), (15) polyoxyethylated lauryl ether surfactant (Brij 30), (20) poly(vinylpyrrolidone) (PVP), (1,12,32−35) sodium dodecyl benzene sulfonate (SDBS), (36) sodium dodecyl sulfate (SDS), (28−30) sodium polyacrylate, (36) Triton X-100, (19,23) among others.
This study has been conducted with the purpose of investigating the influence of PVP and SDS on the mean size, morphology, and antibacterial activity of copper oxide nanoparticles synthesized by the reduction method.

Results and Discussion

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The effect of operational parameters, such as the type of surfactants, concentration, and addition conditions, on the synthesis of nanoparticles has been studied. In our experiment, we choose sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP-300 K) as surfactants. Using the method described in the Experimental Section, it was possible to synthesize copper oxide nanoparticles. By changing various parameters of the synthesis, samples with different crystalline characteristics, mean sizes, particle size distributions, and morphologies were obtained. First, the effect of SDS and PVP-300 K in the synthesis of nanoparticles was investigated. Second, the concentration of PVP-300 K was studied. Then, the effect of adding the dispersant at two different times of the synthesis (0 min and 30 min) was evaluated. Finally, we investigated whether the copper oxide nanoparticles had antibacterial activity.

Effect of Dispersant

Two and five samples, respectively, using different concentrations of SDS and PVP-300 K were synthesized (Table 1).
Table 1. Samples Prepared with Dispersant at Different Times and Concentrationsa
 Cu/SDSCu/PVP
sample0 min30 min0 min30 min
MBS010.90   
MDS01 0.90  
MBP01B  0.54 
MBP01  0.81 
MBP01A  1.62 
MDP01   0.81
MDP01A   1.62
a

[Cu2+]/[NaBH4] = 4:3.

The formation of CuO and Cu2O particles from the hydrolysis of Cu2+ ions in aqueous media is known to be a complex process. Many reactions including cationic species have been proposed. NaBH4 can reduce Cu2+ to form copper oxides through various redox reactions. (37) The reductant agent donates electrons to the Cu2+ ions. Although the reaction route and exact mechanism are not very clear, it is presumed that a series of redox reactions can develop throughout the synthesis process.
The literature reports that using sodium borohydride (NaBH4), the reduction of Cu2+ occurs through the electron transfer from borohydride anions formed in aqueous solution. Then, nucleation of the copper atoms takes place. In this sense, three mechanisms have been proposed (38,39)
(1)
(2)
(3)
The formed copper nanoparticles could be oxidized to Cu2O and CuO. (38,40) This oxidation reaction occurs rapidly when the copper atoms react with the dissolved oxygen molecules in the aqueous solution
(4)
(5)
However, in the solid state, Cu2O is slightly more stable than CuO, as indicated by their standard formation enthalpies −166.7 and −155.2 kJ/mol, respectively. This is why excess copper nanoparticles could cause the reduction of cupric oxide to cuprous oxide nanoparticles (41)
(6)
In addition, oxidation of Cu2O can be carried out if the working pH is greater than 12.5 and the ambient temperature remains constant
(7)
Moreover, Cudennec et al. (42) reported that CuO could be formed through a transformation mechanism involving the generation of Cu(OH)2 and, subsequently, dehydration to CuO
(8)
(9)
(10)
(11)
(12)
In the presence of SDS, Cu(OH)2 is stabilized and CuO is formed according to [eq 9]. (28) In fact, SDS being an ionic surfactant can ionize completely in water, generating a dodecyl sulfate ion (DS–). This ion is negatively charged and can attach to Cu2+ cations forming a complex ion DS-[Cu(OH)4]2– according to [eq 10] and it also forms active sites to generate DS-[Cu(OH)2]. Then, CuO can be produced by dehydration of Cu(OH)2. Simultaneously, DS– anions are released [eq 12]. (29,32)
In addition, Shahmiri et al. (43) propose a third mechanism for the formation of CuO nanostructures that includes three stages when PVP is used
(13)
(14)
(15)
PVP has the structure of a polyvinyl skeleton with polar groups (amide group). The amide group appears to be the most polar because they can donate and accept hydrogen bonds on both O and N atoms. The amide group donates lone-pair electrons that form a coordinative interaction with Cu2+ ions, thus creating a complex compound [eq 13]. PVP acts as a stabilizer for dissolved metallic salts through steric and electrostatic stabilization of the amide groups of the pyrrolidone rings. When the OH– concentration is high enough, intense blue Cu(OH)2 is formed [eq 14], indicating supersaturation due to the hydroxylation reaction. Then, a dehydration process is proposed [eq 15]. Yagi (18) and Zhang et al. (44) confirmed that it is possible to obtain Cu2O directly with NaBH4 if there is a sufficient amount of PVP in the medium.
(16)

Effect of the Dispersant Nature

Copper oxide nanoparticles were obtained using SDS (Cu/SDS = 0.90) and PVP (Cu/PVP = 0.81). Energy-dispersive X-ray spectroscopy (EDS) allowed for the elemental analysis of the nanoparticles. Figure 1a,b shows the EDS spectrum of samples MBS01 (Cu/SDS = 0.90) and MBP01 (Cu/PVP = 0.81). The EDS spectra show the K and L emission peaks for copper and oxygen. No other peak belonging to any other element was detected, indicating that the as-synthesized nanoparticles did not contain impurities.

Figure 1

Figure 1. EDS spectrum of (a) samples MBS01 and (b) MBP01 and (c) X-ray diffraction (XRD) spectra of copper oxide nanoparticles obtained at different ratios of Cu/SDS = 0.90 (MBS01) and Cu/PVP = 0.81 (MBP01).

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The XRD spectra of the as-prepared samples MBS01 and MBP01 show typical X-ray diffraction patterns (Figure 1c). The diffraction peaks are well indexed to those corresponding to CuO with the tenorite monoclinic structure (JCPDS card no. 00-41-254) with lattice parameters a = 4.68 Å, b = 3.42 Å, c = 5.12 Å, and β = 99.42°. Similar results were previously reported by Ganga et al., (28) Rao et al., (29) Reddy et al., (30) and Siddiqui et al. (32) when SDS was used as a dispersant and also by Mayekar et al. (33) and Shahmiri et al. (43) when PVP was used as a dispersant. Further, the elemental analysis of samples MBS01 (Cu = 39.72%, O = 60.28%) and MBP01 (Cu = 43.23%, O = 56.77%) shows that the calculated atomic Cu/O ratio is 0.7 and 0.8, respectively, which is close to 1.0 (the theoretical value for CuO). In this sense, the results of EDS analysis confirm the formation of CuO determined by XRD. In this case, both SDS and PVP not only contribute to dispersion of nanoparticles but also favor the formation of CuO by immediately oxidizing all of the copper formed [eqs 1–3] to tenorite according to eq 5. In addition, if any cuprite is formed (Cu2O), it is immediately oxidized to tenorite [eq 7]. Also, SDS and PVP molecules stabilize Cu(OH)2 for its conversion to CuO according to eqs 9 and 15, respectively. (42,43)
Through transmission electron microscopy (TEM), it was possible to analyze the morphology and size distribution of copper oxide nanoparticles. Figure 2a (sample MBS01) and Figure 2b (sample MBP01) show the presence of well-dispersed CuO nanoparticles. The TEM micrograph of sample MBS01 (Cu/SDS = 0.90) shows spherical nanoparticles when SDS is used (Figure 2c,d).

Figure 2

Figure 2. TEM micrographs of CuO nanoparticles prepared at different ratios of (a) Cu/SDS = 0.9 and (b) Cu/PVP = 0.81 and details of nanoparticles prepared with (c, d) SDS and (e, f) PVP.

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SDS can be dissolved in water, generating a negative ion (DS–) that can attach to Cu2+ cations forming a complex favoring the formation of spherical CuO nanoparticles. (28) SDS is also known to be highly effective in influencing the morphology of nanoparticles through the interactions between the SDS molecule and the precursor nuclei of nanoparticles. However, excess SDS and, therefore, excess DS– can be adsorbed on the surface of CuO nanocrystals during the transformation of Cu(OH)2, inducing the formation of anisotropic branched structures. Likewise, the morphology and the size of CuO nanoparticles can be monitored if the concentration of SDS does not exceed a certain limit. In fact, diverse shapes of CuO nanostructures were obtained when different Cu/SDS ratios were used. Formation of CuO nanorods (28) (Cu/SDS = 0.1), CuO facets broken flower nanoparticles (29) (Cu/SDS = 0.2), CuO rod- and flake-shaped nanoparticles (30) (Cu/SDS = 0.6), and cubelike nanoparticles (32) (Cu/SDS = 3.7) have previously been reported.
Distribution of the nanoparticle size of sample MBS01 (Cu/SDS = 0.9) is shown in the upper left-hand corner of Figure 2a. It shows a bimodal distribution of the particle size ranging from 1.1 to 36.2 nm with a mean diameter of 8.2 ± 6.9 nm. The estimated mean diameter was determined using ImageJ software. The TEM micrograph of sample MBP01 (Cu/PVP = 0.81) is presented in Figure 2b. Figure 2e,f shows semispherical nanoparticles. In fact, PVP is used as a control agent that promotes preferential growth on certain specific crystal faces while obstructing others. When PVP was added into the solution, the active molecules of surfactant were adsorbed on specific crystal planes of nanocrystals because the adsorption energy of surfactant on different crystal planes is significantly different. (1) With a suitable concentration of PVP, the surfaces of CuO nanoparticles are almost covered by PVP. Then, equiaxial growth occurred, and spherical nanoparticles were obtained. However, with a similar Cu/PVP ratio, Mayekar et al. (33) (Cu/PVP = 0.75) and Shahmiri et al. (43) (Cu/PVP = 0.82) synthesized CuO nanoparticles with sheet-shaped structures were obtained. The distribution of the size of sample MBP01 shows a size distribution ranging from 0.7 to 9.5 nm with a mean diameter of 4.5 ± 1.2 nm, as illustrated in the histogram in the upper left-hand side of Figure 2b. We can observe that with similar Cu/SDS and Cu/PVP ratios, different sizes of particles were obtained. The effect of the Cu/dispersant ratio in the synthesis of nanoparticles can favor or interfere with the mechanisms involved in the formation of nanoparticles. According to LaMer et al., (45) the nanoparticle formation mechanism has two stages: nucleation and growth. (46) The polymeric dispersant (PVP) shows a tendency to favor the nucleation step before the growth of the nuclei. In the presence of PVP, the average size of the nanoparticles may decrease because the nucleation process of CuO takes place until the critical radius is reached.
Finally, the crystallite size is calculated using the Scherrer formula from the width of the (111) plane of XRD spectra and is found to be 13.4 and 17.0 nm for samples MBS01 and MBP01, respectively (Table 2). When SDS was used, similar crystallite mean diameters of 13.5 and 15.0 nm were, respectively, reported by Ganga et al. (28) and Rao et al. (29) In contrast, a bigger crystallite size of 52.1 nm was reported by Mayekar et al. (33) when PVP was employed.
Table 2. Average Diameter and the Size of Crystallite Obtained for Each Samplea
sampleCu/SDSCu/PVPcrystalline featuremean diameter (nm)crystallite size (nm)
MBS010.90b CuO8.2 ± 6.9213.4
MDS010.90 (30′) Cu2O8.5 ± 5.2837.1
MBP01B 0.54bCuO11.6 ± 1.4612.1
MBP01 0.81bCuO4.1 ± 1.9314.9
MBP01A 1.62bCu2O41.6 ± 12.8030.3
MDP01 0.81 (30′)CuO/Cu2O6.0 ± 3.811.9
MDP01A 1.62 (30′)CuO/Cu2O13.1 ± 5.512.6
a

[Cu2+]/[NaBH4] = 4:3.

b

Added when the reaction takes place.

Effect of the Metal/PVP Ratio

Besides the concentration of the metal precursor, the variation of the metal/PVP ratio could have a significant effect on the size and the morphology of the metal nanoparticles prepared by chemical reduction. To investigate the effect of PVP on nanoparticle synthesis, the concentration of PVP (300 000 g/mol) was varied from 3 to 10 g/L.
Figure 3a,b shows the EDS spectrum of samples MBP01A (Cu/PVP = 1.62) and MBP01B (Cu/PVP = 0.54), respectively. The K and L emission peaks for copper and oxygen are clearly observed. No other peak was detected, which implies that there were no impurities. This indicates that high-purity copper oxide nanoparticles were obtained.

Figure 3

Figure 3. EDS spectrum of samples (a) MBP01A and (b) MBP01B and (c) XRD spectra of copper oxide nanoparticles prepared at different Cu/PVP ratios (1.62; 0.81; 0.54).

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Figure 3c shows the typical powder X-ray diffraction (XRD) patterns of the as-prepared samples MBP01A, MBP01, and MBP01B with addition of different concentrations of PVP (Table 1). The XRD spectrum of MBP01A exhibits interplanar distances calculated for (111), (200), (211), (220), (311), (222), and (400) that match well with the standard data. These results confirm, according to JCPDS card no. 005-0667 (space group Pn3m, a = 4.23 Å), that cubic-phase cuprous oxide (Cu2O) with a cuprite structure was obtained. This result is in agreement with those previously reported by Borgohain et al., (12) Bai et al., (1) Zhang et al., (47) and Zhang et al. (34) when PVP was used as a surfactant. Furthermore, according to the EDS analysis of MBP01A (Cu = 61.3%, O = 38.7%), the calculated atomic Cu/O ratio is 1.6, which is close to the theoretical value of 2.0 for Cu2O. Then, the results of EDS analysis confirm that Cu2O nanoparticles were obtained, which is in agreement with the XRD results. Formation of Cu2O can occur through several mechanisms: copper nanoparticles can be oxidized to Cu2O [eqs 1–4], excess copper nanoparticles can oxidize cupric oxide nanoparticles to obtain cuprite [eq 6], and if the concentration of NaBH4 is adequate, it is possible to reduce any possible tenorite to cuprite [eq 16].
Samples MBP01B and MBP01 show diffraction peaks that can be indexed to the phase of cupric oxide (CuO), which is in agreement with the results reported previously by Mayekar et al. (33) and Shahmiri et al. (43) In this case, both samples show typical powder diffraction patterns corresponding to a cuprite structure (JCPDS card no. 005-0667 space group Pn3m, a = 4.23 Å). Scherrer’s formula allowed us to estimate the mean crystallite diameters, which were 30.3, 14.9, and 12.1 nm for samples MBP01A, MBP01, and MBP01B, respectively. Similar crystallite mean diameters of 45 nm for Cu2O and 52.1 nm for CuO nanoparticles were previously reported by Borgohain et al. (12) and Mayekar et al., (33) respectively.
As a result, two types of copper oxides were obtained using different Cu/PVP ratios. Cu2O nanoparticles were obtained with a Cu/PVP ratio of 1.62 while nanoparticles of CuO were obtained with lower ratios (0.54 and 0.81). PVP has the structure of a polyvinyl skeleton with polar groups of oxygen and nitrogen that have pairs of free electrons to donate and form an interaction coordinated with copper ions, creating a PVP–Cu2+ compound [eq 13]. If the concentration of PVP is low, it is possible that the complex of PVP–Cu2+ could be reduced to PVP–Cu1+ first (48) and then copper oxide Cu+ (Cu2O) can be formed. Another possibility is that PVP concentration was high enough to directly produce Cu2O by reduction of Cu2+ with NaBH4 according to [eq 16]. (18,44) However, if the concentration of PVP increases, the CuO nanoparticles could be formed by the dehydration process according to [eq 15].
Figure 4 shows the particle size distribution of copper oxide nanoparticles when PVP was used at different concentrations. The three samples show the presence of well-dispersed copper oxide nanoparticles. The distribution of size and mean diameter for each sample is shown in the upper left-hand side of Figure 4. Figure 4a shows a distribution of the particle size ranging from 23.8 to 73.9 nm with a mean diameter of 41.6 ± 12.8 nm for Cu/PVP = 1.62 (sample MBP01A). Cu2O nanoparticles with bigger mean diameters were previously reported by Bai et al., (1) Zhang et al., (34) and Zhang et al. (44) when a small Cu/PVP ratio was used (0.01–0.05). Figure 4b,c shows the distribution of the CuO nanoparticle size ranging from 8.6 to 14.6 nm with a mean diameter of 11.6 ± 1.5 nm (Cu/PVP = 0.54) and from 0.5 to 13.2 nm with a mean diameter of 4.1 ± 1.9 nm (Cu/PVP = 0.81). Details are presented in Table 2. In contrast with this result, a bigger distribution of CuO nanoparticles from 100 to 200 nm was reported by Mayekar et al. (33) when a similar Cu/PVP ratio (Cu/PVP = 0.82) was used.

Figure 4

Figure 4. TEM micrographs of copper oxide nanoparticles prepared at different Cu/PVP ratios: (a) 1.62, (b) 0.81, and (c) 0.54. (d–i) Details of nanoparticles prepared with PVP at different concentrations.

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TEM images show that semispherical CuO nanoparticles were obtained when Cu/PVP ratios of 0.54 and 0.81 were used. In contrast, Mayekar et al. (33) and Shahmiri et al. (43) have described the formation of CuO nanosheets when a similar ratio of Cu/PVP (0.64–0.75) and Cu/PVP (0.82) was used.
In fact, morphology, size, orientation, and dispersion of nanoparticles could be controlled by in situ polymer-assisted particle growth. The polymeric dispersant (PVP) presents the tendency to favor the nucleation step before the growth of the nuclei. In our case, the optimal molar ratio of Cu/PVP seems to be 0.81. When the Cu/PVP ratio is greater than 0.81, the average size of the copper oxide nanoparticles increases drastically, whereas when the Cu/PVP ratio is less than 0.81, the particle size increases slightly. PVP as an effective stabilizer and protecting agent can limit particle growth and prevent the particles from aggregating. But PVP can also induce the reduction of Cu2+ and speed up the kinetics of formation of particles [eqs 13–16], which cannot disperse as quickly as they are formed. If the concentration of PVP is high, it restrains the diffusion of the copper oxide nanoparticles. Therefore, dispersion of the nanoparticles became more difficult and aggregation occurred again, leading to an increase in the nanoparticle size. For this reason, the nanoparticles obtained with a Cu/PVP ratio of 0.54 are slightly larger than those obtained with 0.81. Details of the nanoparticles prepared with different concentrations of PVP are presented in Figure 4d–i.
In Figure 4d–i, a panoramic view of well-dispersed nanoparticles of copper oxides is presented. Figure 4d,e shows semispherical Cu2O nanoparticles when Cu/PVP = 1.62 was used (sample MBP01A). Figure 4f–i indicates that spherical nanoparticles of CuO were obtained with Cu/PVP = 0.81 (sample MBP01) and Cu/PVP = 0.54 (sample MBP01B). It is known that PVP molecules, as surfactants, play an important role in inducing the formation of nuclei and directing the growth of metal oxide crystals through selective and kinetic adsorption on the surface of particles. (16) Wu et al. reported that nonspherical nanoparticles can be obtained when PVP is used. (49) It is possible that PVP can be adsorbed on specific faces of Cu2O, altering their growth rates, thus allowing for the generation of nonspherical shapes.

Effect of Dispersant Addition

To study the effect of dispersant addition once the synthesis had started, two samples were prepared by adding SDS and PVP 30 min after starting the reaction. Figures 1a and 5a show the EDS spectrum of samples MBS01 and MDS01 prepared with addition of SDS at 0 and 30 min of starting the reaction, respectively. Only the K and L emission peaks for copper and oxygen were observed. From the elemental analysis of MDS01 (Cu = 61.69%, O = 38.31%), the atomic Cu/O ratio can be calculated to be 1.6, which is close to the theoretical value of 2.0 for Cu2O.

Figure 5

Figure 5. EDS spectrum of (a) sample MDS01 and XRD spectra of copper oxide nanoparticles prepared at different times of dispersant addition: (b) Cu/SDS = 0.9 (0 min) and 0.9 (30 min), (c) Cu/PVP = 0.81 (0 min) and 0.81 (30 min), and (d) Cu/PVP = 1.62 (0 min) and 1.62 (30 min).

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Figure 5b shows the typical powder X-ray diffraction (XRD) patterns of the as-prepared MBS01 (Cu/SDS = 0.90; 0 min) and MDS01 (Cu/SDS = 0.90; 30 min). The diffraction peaks of MBS01 show the formation of cupric oxide (CuO) with the monoclinic structure of tenorite (JCPDS card no. 00-41-254) and a = 4.68 Å, b = 3.42 Å, c = 5.12 Å, and β = 99.42° as lattice parameters. The XRD spectrum of sample MDS01 confirms that a cubic phase of cuprous oxide (Cu2O) presenting a cuprite structure (JCPDS card no. 005-0667, space group Pn3m, a = 4.23 Å) was formed.
Figure 5c,d shows the XRD patterns of samples MBP01 (Cu/PVP = 0.81; 0 min), MBP01A (Cu/PVP = 1.62; 0 min), MDP01 (Cu/PVP = 0.81; 30 min), and MDP01A (Cu/PVP = 1.62; 30 min). All peaks in Figure 5c can be well indexed to the monoclinic structure of cupric oxide (CuO) (JCPDS card no. 00-41-254). However, small diffraction peaks arising from Cu2O appear in the XRD patterns. Sample MDP01A (Figure 5d) exhibits peaks that confirm the formation of cuprous oxide (Cu2O) with a cuprite structure (JCPDS card no. 005-0667, space group Pn3m, a = 4.23 Å). However, small diffraction peaks of CuO arise in the XRD patterns. Then, XRD spectra show that nanoparticles prepared with PVP added 30 min after starting the reaction are a mixture of CuO and Cu2O. This result is in agreement with results reported previously by Liu et al. (35) In addition, the calculated atomic Cu/O ratios of MDP01 (Cu = 60.15%, O = 39.85%) and MDP01A (Cu = 61.48%, O = 38.52%) from EDS analysis were 1.51 and 1.59, which are close to theoretical values of 1.50 (CuO·3Cu2O) and 1.60 (2CuO·3Cu2O), respectively. These results confirmed that the nanopowder produced was a mixture of CuO and Cu2O, which is in agreement with the XRD results.
The results show that when SDS is used, cuprite nanoparticles are produced, whereas when PVP is used, a mixture of copper oxide nanoparticles is obtained. During the first 30 min, there is no dispersant in the medium. Then, the reduction reaction of Cu2+ ions by BH4– is carried out, producing Cu2O. Several possible mechanisms can be proposed. Cu nanoparticles produced [eqs 2 and 3] are subsequently oxidized to Cu2O [according to eq 4] and CuO [according to eq 5]. In addition, some of the CuO produced can be reduced to Cu2O by Cu nanoparticles [eq 6]. After 30 min, the added SDS is adsorbed on the surfaces of the formed nanoparticles, dispersing them without affecting the reaction mechanism. In the case of PVP addition, the remaining Cu2+ ions form CuO [eqs 13 and 15]. For this reason, a mixture of copper oxides is obtained.
Figure 6a shows well-dispersed Cu2O nanoparticles in sample MDS01 (Cu/SDS = 0.90; 30 min). It could be presumed that stabilization of the copper oxide nanocrystals was carried out through coordinative interactions between the oxygen atoms present in SDS and on the surface of nanoparticles. (50)Figure 6a shows a bimodal distribution of the particle size ranging from 2 to 19 nm and from 22 to 39 nm. The mean diameter calculated by ImageJ was 8.5 ± 5.3 nm. In this case, semispherical nanoparticles were obtained. No significant difference in mean diameter and shape was observed when SDS was added 30 min after the reaction started.

Figure 6

Figure 6. TEM micrographs of copper oxide nanoparticles prepared at different ratios of (a) Cu/SDS = 0.9 (30 min), (b) Cu/PVP = 1.62 (30 min), and (c) Cu/PVP = 0.81 (30 min) and details of nanoparticles prepared with (d, e) SDS and (f, i) PVP at different concentrations.

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Sample MDP01 (Cu/PVP = 0.81; 30 min) shows a bimodal particle size distribution ranging from 1.5 to 9.8 nm and from 10.0 to 22.8 nm with a mean diameter of 6.0 ± 3.8 nm (Figure 6b), while MDP01A presents particle sizes from 1.5 to 27 nm with a mean diameter of 13.1 ± 5.5 nm (Figure 6c). A similar mean diameter of sample MDP01A was reported by Liu et al. (35) for spherical copper oxide nanoparticles (Cu2O and CuO). Figure 6d–i reveals the morphologies of copper oxide nanoparticles synthesized with different amounts of surfactant. By adding surfactant 30 min after the beginning of the reaction, irregular nanoparticles are observed, while spherical nanoparticles are obtained using the surfactant at the beginning of the reaction. When the Cu/PVP ratio increases from 0.81 to 1.62, the average particle size changes from 6.0 ± 3.8 to 13.1 ± 5.5 nm. The presence of PVP seems beneficial to the growth of cubes and hexagonal nanoparticles (Figure 6f–g). If the concentration of PVP increases (sample MDP01A), then all cuprous oxide surfaces are almost covered by PVP. Then, an equiaxial growth occurs, and hexagonal or semispherical cuprous oxide nanoparticles were obtained. If the concentration of PVP is halved (sample MDP01), only a part of the cuprous oxide surface is covered by PVP, resulting in an anisotropic growth of nanocrystals.
Table 2 summarizes the mean diameter and the crystallite size of the different samples. For the Cu/PVP = 0.81 ratio, a slight difference in nanoparticles size is observed when PVP is added at the beginning and at 30 min of the reaction. However, the difference in nanoparticle size is more evident when a smaller amount of PVP (Cu/PVP = 1.62) is added at 0 or 30 min from the start of the reaction. In fact, when PVP is added at the beginning of the reaction, particles of up to four times the size of those produced when the dispersant is added at 30 min are obtained.
Using Scherrer’s formula, the crystallite diameters were determined. The values are 37.1, 11.9, and 12.6 nm for samples MDS01 (Cu/SDS = 0.90; 30 min), MDP01 (Cu/PVP = 0.81; 30 min), and MDP01A (Cu/SDS = 1.62; 30 min), respectively. A smaller crystallite mean diameter of 8 nm for a mixture of Cu2O and CuO nanoparticles was previously reported by Liu et al. (35)

Coating Cotton Fabric

By applying ultrasonic waves, it was possible to incorporate the nanoparticles from samples MDS01 and MDP01 into cotton fabrics of approximately 11.8 cm2 area (Figure 7a). El-Nahhal et al. (51) reported that CuO nanoparticles can be stabilized in cotton fibers thanks to the interaction of some surfactants such as SDS. In fact, the surfactant provides better adhesion of the nanoparticles to the surface of the cotton. Indeed, the use of surfactants has improved the durability of nanoparticles and decreased their leaching. This behavior has been observed by El-Nahhal et al. (51,52) for SDS with ZnO and CuO nanoparticles.

Figure 7

Figure 7. (a) Cotton fabric before and after nanoparticle deposition and scanning electron microscopy (SEM) images of (b) the original cotton fiber, (c) MDS01-CF, (d) MDS01-CF after washing, (e) MDP01-CF, and (f) MDP01-CF after washing.

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The morphology of the fiber surface area before and after deposition of copper oxide nanoparticles was studied using SEM. Figure 7b shows the original cotton fiber before being impregnated with nanoparticles; we can observe grooves and fibrils on the surface of the fabric. SEM images of copper oxide nanoparticles covering cotton fibers are presented in Figure 7c (MDS01-CF) and Figure 7e (MDP01-CF). It is evident that it is possible to incorporate the copper oxide nanoparticles into cotton fibers when ultrasound waves are used. However, some agglomerated nanoparticles were observed. To determine if the particles would be fixed in the fabric or not, the cotton fabric was washed five times in a mini-washing machine with ultrapure water (Millipore Inc.). The copper oxide nanoparticles released into solutions were evaluated by atomic absorption spectroscopy (AAS). The tissues impregnated with ultrasound waves retain 95% (MDS01-CF) and 96% (MDP01-CF) of the copper oxide nanoparticles after having been washed five times (see Figure 7d,f). Based on this result, we can indicate that nanoparticles are strongly and physically adsorbed on the cotton surface, since these particles are not easily removed after several washes. El-Nahhal et al. (51) evaluated the stability of CuO nanoparticles incorporated into cotton fabric in the presence of SDS when 10 washing cycles was used. In our case, the 5% loss of CuO is not very significant compared to the 25% loss reported by El-Nahhal et al. (51)
Depending on their antibacterial activity, these materials can be used to design medical textiles, protective clothes and covers, and many others with the purpose of reducing the possibility of nosocomial infections. (53) Preliminary Kirby–Bauer tests show that there is some antibacterial activity (Table 3). However, further study in this field is needed.
Table 3. Antibacterial Activity (mm) of Copper Oxide Nanoparticle Sols against Gram-Positive and Gram-Negative Strains
sampleMBP01MBP01BMDS01MBP01AMDP01MDP01Araw cotton fabricMDS01-CFMDP01-CF
crystalline featureCuOCuOCu2OCu2OCuO and Cu2OCuO and Cu2O
mean diameter (nm)4.1 ± 1.911.6 ± 1.58.5 ± 5.341.6 ± 12.86.0 ± 3.813.1 ± 5.5
E. coliATCC 1053614 18 1512negativepositivepositive
P. aeruginosaATCC 1014517 16 3418negativepositivepositive
S. aurusCCM 395319 28152017negativepositivepositive
S. aurusMRSA ATCC 902722 29 2315negativepositivepositive

Antibacterial Activity

The antimicrobial susceptibility of copper oxide nanoparticles against four strains was examined. To determine if a strain was susceptible, moderately or highly resistant to the synthesized nanoparticles, the Kirby–Bauer diffusion method as an antimicrobial susceptibility test was performed. For the antibacterial test, two types of strain, Gram-positives and Gram-negatives, were used as bacilli. Staphylococcus aureusstrain (CCM 3953) and S. aureusMRSA strain (ATCC 9027) as Gram-positives and Escherichia colistrain (ATCC 10536) and Pseudomonas aeruginosastrain (ATCC 10145) as Gram-negative strains were used. Six samples of nanoparticles exhibiting different morphologies, average size, and chemical composition were tested. Samples MBP01 and MBP01B are tenorite and samples MDS01 and MBP01A are cuprite, while samples MDP01 and MDP01A are a mixture of copper oxides (mainly tenorite with cuprite).
In this test, disposable Petri dishes, inoculated with Gram-positive and Gram-negative bacteria at a concentration of 105 to 106 CFU/mL, were used. The disposable plate containing a specific bacterium was inoculated with the copper oxide nanoparticle sols. After 24 h of incubation at 35 °C, the inhibition zones were measured. Table 3 shows the diameters of the inhibition zones (in millimeters). The antibiotics, vancomycin and gentamicin, for Gram-positive and Gram-negative bacteria were, respectively, used as controls.
In the case of tenorite (CuO), only sample MBP01 with the smallest average size (4.1 ± 1.9 nm) shows antibacterial activity against all strains. Shahmiri et al. (43) and Naika et al. (54) reported a similar inhibition of the diameter zone against E. coli and S. Aurus when CuO nanoparticles were used. In addition, a greater antibacterial susceptibility against the S. aureusMRSA strain was evidenced. Sample MBP01B (13.1 ± 5.5 nm) did not show positive results for any strains. For cuprite (Cu2O), only sample MDS01 containing small nanoparticles (8.5 ± 5.3 nm) shows some antibacterial activity for all strains. In this case, the highest zones of inhibition were observed for the S. aurus and S. aurus MRSA strains. For the sample (MBP01A) with a larger nanoparticle mean size (41.6 ± 12.8 nm), antibacterial activity was observed only for the S. aurus strain. Instead, the two samples of the copper oxide mixture (CuO–Cu2O) show bactericidal activity against the four strains. However, it is observed that the sample with smaller nanoparticles (6.0 ± 3.8 nm) shows a greater zone of inhibition (sample MDP01). Furthermore, the zone of inhibition for the P. aureginosa strain was remarkable.
Comparing the Gram-negative bacteria, we can observe that for the E. coli strain, the diameters of the inhibition zone are similar when samples of CuO and CuO–Cu2O nanoparticles with close mean diameters were used (Figure 8). Azam et al. (55) reported analogous results using CuO nanoparticles with a mean size of 5 nm. For the P. aeruginosa strain, the best response to the antibacterial test was provided by the sample composed of both copper oxides (CuO and Cu2O). If we compare samples with nanoparticles having similar diameters, MBP01B (CuO; 11.6 ± 1.5 nm) and MDP01A (CuO–Cu2O; 13.1 ± 5.5 nm), we can notice that only the sample with cuprite exhibits antibacterial activity. In this case, inhibition of bacteria is enhanced due to the presence of cuprite. This effect is observed even for the larger nanoparticles. In addition, the inhibition diameters for the other samples remain almost constant. Finally, we can observe that samples MBP01, MDP01, and MDP01A show higher zones of inhibition against the P. aeruginosa strain than against the E. coli strain. Similar results were reported by Das et al. (6) when the bactericidal activity of CuO nanoparticles against these two strains was compared.

Figure 8

Figure 8. Results of the diffusion test of copper oxide nanoparticles against Gram-positive and Gram-negative strains.

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In the case of S. aureus, it is observed that the smallest diameter of the inhibition zone is reported for sample MBP01A, which present larger Cu2O nanoparticles (41.6 ± 12.8 nm). The largest inhibition zone is reported for sample MDS01 (8.5 ± 5.3 nm), which suggests that small Cu2O nanoparticles have a positive effect on bacterial inhibition. (56) Finally, we observe that for each sample, when the mean diameter of the nanoparticle decreases, the diameter of the inhibition zone increases (Table 3).
The interaction between Gram-positive bacteria and CuO and Cu2O nanoparticles with a smaller mean size diameter seems to be stronger than the interaction with Gram-negative bacteria; this is due to the difference in cell walls between the Gram-positive and Gram-negative bacteria. Bacteria E. coli and P. auriginosa have a cell wall that is made up mainly of lipids, proteins, and lipopolysaccharides (LPSs), providing an effective shield against biocides. In contrast, Gram-positive bacteria, such as S. aureus and S. aurusMRSA, do not have LPSs in their cell wall. (57) Similar bactericidal results were previously reported when silver nanoparticles were used. (58) Therefore, the bacterial susceptibility obtained with copper oxide nanoparticles showed encouraging results. However, the MIC of each sample must still be determined.
Preliminary results suggest that copper oxide nanoparticles can be used as antimicrobial agents for the treatment of infections caused by the bacteria studied. (59) Currently, the exact bactericidal mechanism of copper oxide colloid nanoparticles on bacteria has not been identified. Certainly, there are many mechanisms that can result from the direct interaction between copper oxide nanoparticles and the outer membrane surface of bacteria. In this sense, some mechanisms have been proposed to interpret the antibacterial behavior of metal oxides. (6)
Pena et al. (60) and Kim et al. (61) have proposed different forms of action for copper oxide nanoparticles. One possibility is that the released copper ions, in an oxidation process, can intercalate with the nucleic acid strands when they interact with DNA molecules. In this way, copper ions cause a disorder of the helical structure of DNA molecules by joining them and cross-linking within and between the nucleic acid strands. Also, copper ions disrupt biochemical processes within bacterial cells. (60) Another possibility is the action of radical species that are very active. Reactive hydroxyl radicals, which are generated by copper oxides, can oxidize proteins. In this manner, by cleaving DNA and RNA molecules, lipids are oxidized, damaging their membrane. (54) Free oxygen radicals are powerful oxidizing agents. They can break down the cell wall of bacteria through a series of oxidation–reduction reactions. (61) Oxygen free radicals are generated from excited electrons on the surface of Cu2O nanoparticles. Presently, the exact mechanism of action of CuO and Cu2O is not known yet. The bactericidal property of nanoparticles can be associated with the mechanism of copper ions or free radical-generation species or both. Similar results of antibacterial behavior were previously reported. (11,55,56,62)
The antibacterial properties of raw cotton fabric and cotton/nanoparticles were examined against both Gram-negative and Gram-positive bacteria using the disc diffusion method (zone of inhibition test). A small inhibition halo was observed, which shows positive results. However, it is necessary to carry out more studies to determine the optimal nanoparticle dosage per cm2 of cotton fabric. The raw cotton fabric did no show a zone of inhibition.

Conclusions

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Nanoparticles of cupric and cuprous oxides with average diameters from 4.1 ± 1.9 to 41.6 ± 12.8 nm have been obtained using copper sulfate as a source of copper ions and sodium borohydride as a reducing agent. The EDS analysis confirmed the formation of copper oxide nanoparticles, since only elemental signals of copper and oxygen were observed.
We can conclude that the crystalline characteristics, particle size distribution, and the morphology of the nanoparticles change with the variation of the experimental conditions and the nature of the dispersant material used. XRD spectra confirm that tenorite nanoparticles (CuO) were obtained when SDS (Cu/SDS = 0.90; 0 min) and PVP (Cu/PVP = 0.54; 0 min and Cu/PVP = 0.81; 0 min) were used. Cuprite nanoparticles (Cu2O) were obtained when PVP (Cu/PVP = 1.62; 0 min) and SDS (Cu/SDS = 0.90; 30 min) were used. On the other hand, a mixture of copper oxides (CuO and Cu2O) was obtained by adding PVP at two different conditions (Cu/PVP = 0.81; 30 min and Cu/PVP = 1.62; 30 min).
TEM images show that spherical nanoparticles are obtained using SDS. In fact, it can be concluded that the morphology of nanoparticles is not affected by the use of SDS at 0 min or 30 min after the start of the reaction. However, the nanoparticle shape is affected by the use of PVP at different times of the reaction. Semispherical nanoparticles were obtained with two different Cu/PVP ratios (Cu/PVP = 0.54; 0 min and Cu/PVP = 0.81; 0 min). Semispherical and hexagonal nanoparticles were obtained when PVP was added at two different times of the reaction (Cu/PVP = 1.62; 0 min and Cu/PVP = 1.62; 30 min). The influence on morphology is more evident when PVP (Cu/PVP = 0.81; 30 min) is used, since rectangular, hexagonal, and spherical nanoparticles were obtained (sample MDP01).
The influence of the dispersant on the nanoparticle size is evident when PVP is compared to SDS. The size of CuO nanoparticles decreases when the Cu/PVP ratio increases from 0.54 until 0.81. For CuO–Cu2O nanoparticles, the mean size increased when the Cu/PVP ratio increased from 0.81 until 1.62. In this case, the amount of PVP was too low to prevent nanoparticle growth. (22)
The results of the Kirby–Bauer method demonstrated that the growth and multiplication of the E. coli, P. aeruginosa, S. aureus, and S. aureus MRSA bacteria could be inhibited by the copper oxide nanoparticles. The results show that small CuO nanoparticles have a bactericidal effect, including samples containing a small quantity of Cu2O. Bigger nanoparticles of tenorite (CuO) do not show bacteriological activity in any case. For cuprite (Cu2O), small nanoparticles show antibacterial activity against the four bacteria, while larger nanoparticles show only slight antibacterial activity against S. aurus. Based on the results obtained, we can conclude that the optimal Cu/dispersant ratios are 0.90 (Cu/SDS) and 0.81 (Cu/PVP). The nanoparticles obtained under these conditions show a higher antibacterial activity against the tested strains.
XRD revealed that CuO–Cu2O and CuO nanoparticles coated onto cotton fibers are in the crystalline form of the monoclinic phase. The use of ultrasonic waves allows us to retain up to 96% of the nanoparticles adhering to the fabric after washing them up to five times. The minimum inhibitory concentration (MIC) using the standard microdilution method is an ongoing test. The antibacterial test performed on the cotton fabric impregnated with nanoparticles shows positive results. However, more experiments are necessary to determine the optimal ratio of copper oxide nanoparticles per cm2 of fabric.

Experimental Section

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Chemicals

Copper sulfate, CuSO4 (≥98%); sodium borohydride, NaBH4 (98%); ethylenediaminetetraacetic acid, EDTA, C10H16N2O8 (≥98%); potassium hydroxide, KOH (90%); sodium dodecyl sulfate, SDS (≥99%); and poly(vinylpyrrolidone), PVP-300 K (99%) were purchased from Sigma-Aldrich Peru (Lima, Peru). All chemicals were of analytical purity and used as received without further purification. Milli-Q water (18 MΩ cm) was used in all experimental syntheses. The purification system (Millipore, Darmstadt, Germany) is located in our laboratory.

Bacterial Strains

The bacteria tested were P. aeruginosastrain (ATCC 10145) and E. colistrain (ATCC 10536) as Gram-negative strains and S. aureusstrain (CCM 3953) and S. aureusMRSA strain (ATCC 9027) as Gram-positive strains. The bacteriological test was carried out at the Universidad Peruana Cayetano Heredia, Peru.

Copper Oxide Nanoparticle Synthesis

The modified chemical reduction method proposed by Badawy et al. (63) was used for the synthesis of copper oxide nanoparticles. Aqueous solutions of copper sulfate (40 mM), sodium borohydride (30 mM), potassium hydroxide (2,0 mM), ethylenediaminetetraacetic acid (EDTA, 1.0 mM), poly(vinylpyrrolidone) (PVP, 0.25–0.75% v/v), and SDS (20 mM) were used. The synthesis was carried out at room temperature. Copper sulfate solution was added to a 250 mL flask. Certain volumes of potassium hydroxide and EDTA were added. Then, using a glass burette, sodium borohydride was gradually dropped into the copper solution (at a rate of 3 mL/min). To ensure homogenization of the solutions, the reaction was carried out under magnetic stirring at room temperature. As the reaction proceeds, the light blue copper sulfate solution gradually turns into an opaque blue solution. Subsequently, the color of the solution turned reddish-brown, confirming the formation of copper oxides. After completely adding the reducing agent, the solution was stirred continuously for 30 min at room temperature. Then, the respective dispersant was added dropwise. The solution was stirred for a further 40 min. At the end of the reaction time, the nanoparticles were separated by centrifugation (12 000 rpm, 5 min) using a microcentrifuge (Eppendorf 5804). To remove excess copper ions that did not react, the nanoparticles were washed with Milli-Q water at least three times. The filtrate was kept in a desiccator. In the end, a dry copper oxide nanopowder was obtained. A similar procedure was carried out by adding the dispersant agent to the copper sulfate solution. To characterize the nanoparticles and evaluate their bacteriological activity, a certain amount of copper oxide nanopowder was suspended in deionized water using an ultrasonic cleaning container (Fisher Bioblock Scientific).

Characterization Methods for Copper Oxide Nanoparticles

Structural Characterization

Structural analysis was carried out using a Bruker D8 Advance X-ray diffractometer (Karlsruhe, Germany) equipped with a copper anticathode (λ Cu Kα = 1.54056 Å). XRD spectra were obtained in a range of 2θ = 30–100° using a step size of 0.03° (10 s per step as the counting time). The standard database (JCPDS) for XRD was used for phase identification. Using the information obtained from XRD patterns, the crystallite size was determined using the approximate Scherrer equation (D = kλ/ß cos θ). This equation describes the relationship of the crystallite size (D) considering the wavelength of the X-ray radiation (λ = 1.54056 Å), a constant related to the particle shape (k = 0.89 assuming that the particles are spherical), the line width at half maximum intensity of the most important peak (ß), and the diffraction angle (θ).

Elemental Composition Analysis

The sample chemical composition was analyzed using a scanning electron microscope (JEOL JSM 6460LA) coupled with an EDS microprobe (JEOL 1300).

Morphology Analysis

The size and morphology were obtained using transmission electron microscopy, TEM. A Philips CM20-Ultra Twin transmission electron microscope operating at 200 kV (Philips; Eindhoven, the Netherlands) was used. ImageJ software was used to elaborate the nanoparticle size distribution histograms from the TEM images. In this case, the diameters of at least 100 particles were measured. Using ultrasonic equipment, a small portion of nanopowder was dispersed in ethanol (98%) for 1 min. Then, a few drops of the copper oxide nanoparticle solutions were placed on carbon-coated TEM gold grids.

Coating Cotton Fabric

Incorporation of the copper oxide nanocrystals into cotton fibers was carried out by applying ultrasound waves. The literature reports that it is possible to use ultrasound waves to incorporate nanoparticles into textile fibers and porous materials. (64) The nanoparticles were dispersed in 16 mL of Milli-Q water; to ensure a homogeneous dispersion, the vessel was exposed to ultrasonic waves for 10 min. The cotton sample (11 cm2 approximately) was washed with Milli-Q water before being immersed in a small glass beaker containing the dispersed nanoparticles. Then, the cotton fiber was placed in this vessel. The nanoparticles and the cotton fibber sample were placed in a small ultrasonic cleaning container (Fisher Bioblock Scientific) for 30 min. Subsequently, the cotton fibber samples impregnated with the nanoparticles were washed five times and placed in a desiccator. To determine the content of copper not retained in the cotton fiber, the copper concentration in the washing solutions was analyzed using atomic absorption spectroscopy (Varian AA 220). Finally, the cotton fiber was placed in an oven (at 40 °C). The sample was placed in a desiccator for subsequent analysis using XRD and SEM.

Antibacterial Assays of Copper Oxide Nanoparticles

The disc diffusion or Kirby–Bauer method was used to evaluate the antimicrobial susceptibility of copper oxide nanoparticles. (65) After 24 h of incubation at 35 °C, the halos formed, representing the inhibition zones, were measured. Discs containing antibiotics vancomycin and gentamicin were prepared to make the necessary comparisons. The standard dilution method used to determine the minimum inhibitory concentration (MIC) required to inhibit bacterial growth is under investigation.

Author Information

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  • Corresponding Author
  • Authors
    • Mariella Arcos - Sciences Department, Pontifical Catholic University of Peru, Av. Universitaria 1801, Lima 32, Peru
    • Jean Dille - 4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
    • Céline Rousse - LISM, EA 4695, UFR Sciences Exactes et Naturelles, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims cedex 2, France
    • Stéphane Godet - 4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
    • Loïc Malet - 4MAT, Université Libre de Bruxelles, CP 194/03, 50 Avenue Roosevelt, B-1050 Brussels, Belgium
  • Author Contributions

    M.G. conceptualized the idea; proposed the methodology; supervised the project; and wrote, revised, and edited the manuscript. M.A. carried out the experiments; collected and analyzed the data; and wrote a part of the manuscript. J.D. contributed to the TEM analysis and revised and edited the manuscript. C.R. contributed to the SEM and XRD analysis and wrote a part of the manuscript. S.G. provided laboratory facilities and resources. L.M. contributed to the SEM analysis.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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Dr. M.G. thanks the Cayetano Heredia University, Perú, for the antibacterial activity carried out in the Laboratory of Biology. This work was supported by CAP 2012-0098 granted by the Pontifical Catholic University of Peru.

References

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    In this paper, Cu2O nanoparticles were in situ synthesized on cotton fabric through a new simple and cost-effective chem. redn. method using copper sulfate, sodium hydroxide and ammonia. Cotton fabric participates as a reducing agent in redn. of copper sulfate and facilitates synthesis of cuprous oxide in nano-scale as a stabilizer. The produced cotton/nano Cu2O composite were characterized by X-ray diffraction, SEM and Energy-dispersive X-ray spectroscopy. Interaction of Cu2O with cotton fabric in addn. to alteration of cotton functional groups were studied by Fourier transforms IR spectroscopy. The intermediate soln., copper-amine complex, was analyzed by UV-visible spectroscopy. The mech. properties of the cotton/nano Cu2O composite were studied using Instron indicated a higher tensile strain. The antibacterial activity of the fabric samples showed considerable behavior against S. aureus and E. coli. Further, the treated fabric became highly hydrophobic and sensed ammonia and hydrogen peroxide chromatically.
    (d) El-Nahhal, I. M.; Zourab, S. M.; Kodeh, F. S.; Selmane, M.; Genois, I.; Babonneau, F. Nanostructured copper oxide-cotton fibers: synthesis, characterization, and applications. Int. Nano Lett. 2012, 2, 14  DOI: 10.1186/2228-5326-2-14
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    Khodashenas, B.; Ghorbani, H. R. Synthesis of copper nanoparticles: An overview of the various methods. Korean J. Chem. Eng. 2014, 31, 1105– 1109,  DOI: 10.1007/s11814-014-0127-y
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    Synthesis of copper nanoparticles : An overview of the various methods
    Khodashenas, Bahareh; Ghorbani, Hamid Reza
    Korean Journal of Chemical Engineering (2014), 31 (7), 1105-1109CODEN: KJCHE6; ISSN:0256-1115. (Springer)
    The synthesis of metal nanoparticles has received much attention due to their wide range of applications. Copper nanoparticles have attracted much attention due to their unique optical and elec. properties. Copper is relatively cheap in comparison to precious metals like gold and silver and also has high antibacterial properties. This review gives a brief overview of the available research works considering the synthesis of copper nanoparticles by chem., phys., and biol. methods.
  6. 6
    Das, D.; Nath, B. C.; Phukon, P.; Dolui, S. K. Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles. Colloids Surf., B 2013, 101, 430– 433,  DOI: 10.1016/j.colsurfb.2012.07.002
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    Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles
    Das, Dhaneswar; Nath, Bikash Chandra; Phukon, Pinkee; Dolui, Swapan Kumar
    Colloids and Surfaces, B: Biointerfaces (2013), 101 (), 430-433CODEN: CSBBEQ; ISSN:0927-7765. (Elsevier B.V.)
    CuO nanoparticles were synthesized by thermal decompn. methods and characterized by UV-visible spectroscopy, XRD and TEM anal. The resultant particles are nearly spherical and particle size is in the range of 15-30 nm. The antioxidant behavior of synthesized CuO nanoparticles was evaluated by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The free radical scavenging activity of CuO nanoparticles was monitored by UV-visible spectrophotometry. The antibacterial activity of CuO nanoparticles was tested against different bacterial strains. CuO nanoparticles showed efficient antioxidant activity and bactericidal effect against Escherichia coli and Pseudomonas aeruginosa.
  7. 7
    Salavati-Niasari, M.; Davar, F. Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor. Mater. Lett. 2009, 63, 441– 443,  DOI: 10.1016/j.matlet.2008.11.023
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    Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor
    Salavati-Niasari, Masoud; Davar, Fatemeh
    Materials Letters (2009), 63 (3-4), 441-443CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    The present investigation reports, the prepn. of nanoparticles Cu and Cu2O using thermal decompn. and its physicochem. characterization. The nanoparticles copper powder were prepd. using [bis(salicylidiminato)copper(II)], [Cu(sal)2], as precursor. Cu nanoparticles are initially formed and subsequently oxidized to form Cu2O. TEM demonstrated nanoparticles Cu2O with an av. diam. of ≈10 nm. As-prepd. Cu nanoparticles were characterized by x-ray diffraction measurements (XRD), SEM, energy dispersive anal. of x-rays (EDAX), and FTIR. XRD anal. revealed broad pattern for fcc. crystal structure of copper metal and cubic cuprite structure for Cu2O. Optical absorption measured by UV-visible spectroscopy was used to monitor oxidn. course of Cu → Cu2O and to det. the band-gap energy about 2.4 eV for Cu2O nanoshells.
  8. 8
    Zhou, L. J.; Zou, Y. C.; Zhao, J.; Wang, P. P.; Feng, L. L.; Sun, L. W. Facile synthesis of highly stable and porous Cu2O/CuO cubes with enhanced gas sensing properties. Sens. Actuators, B 2013, 188, 533– 539,  DOI: 10.1016/j.snb.2013.07.059
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    Facile synthesis of highly stable and porous Cu2O/CuO cubes with enhanced gas sensing properties
    Zhou, Li-Jing; Zou, Yong-Cun; Zhao, Jun; Wang, Pei-Pei; Feng, Liang-Liang; Sun, Li-Wei; Wang, De-Jun; Li, Guo-Dong
    Sensors and Actuators, B: Chemical (2013), 188 (), 533-539CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
    Highly stable and porous Cu2O/CuO cubes were prepd. by the calcination of the precursor at different temps. (350, 450, and 550°). The precursor which consists of cupric oxalate and cubic Cu2O was obtained by a one-step hydrothermal route with the help of ethylene glycol. The chem. compn. and structure of the products were confirmed by powder x-ray diffraction, SEM, TEM, and XPS. The cube is composed of nanoparticles with diams. around several dozens of nanometers and the calcination temp. has great influence on the size, the amt. of Cu2O and the surface area of the final products. The gas sensing ability of the as-prepd. porous Cu2O/CuO cubes was investigated toward a series of toxic org. mols., in which the sample calcined at 350° exhibits higher sensing response to acetone. The higher sensing response of this sample might be attributed to the heterostructure of CuO and Cu2O and the relatively high surface area.
  9. 9
    Fan, H.; Yang, L.; Hua, W.; Wu, X.; Wu, Z.; Xie, S.; Zou, B. Controlled synthesis of monodispersed CuO nanocrystals. Nanotechnology 2004, 15, 37– 42,  DOI: 10.1088/0957-4484/15/1/007
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    Controlled synthesis of monodispersed CuO nanocrystals
    Fan, Haiming; Yang, Lintao; Hua, Wenshen; Wu, Xingfang; Wu, Zhenyu; Xie, Sishen; Zou, Bingsuo
    Nanotechnology (2004), 15 (1), 37-42CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)
    Controlling the size, shape and structure of nanocrystals is technol. important because of the strong effect of size and shape on optical, elec., and catalytic properties. Monodispersed nanocrystals of CuO were prepd. by the pptn.-pyrolysis method. By controlling the starting materials, reactive concn. and annealing temp., the authors can obtain spherical monodispersed CuO nanocrystals of different sizes or rodlike CuO nanocrystals. The particle sizes of CuO monodispersed nanocrystals can be tuned in the range between ∼7 and 30 nm. The products were characterized by x-ray diffraction, TEM, high-resoln. TEM and the UV-visible absorption spectrum. The absorption spectra of CuO nanocrystals show clear evidence of the quantum size effect. The possible formation mechanism of monodispersed CuO nanocrystals is discussed.
  10. 10
    Shui, A.; Zhu, W.; Xu, L.; Qin, D.; Wang, Y. Green sonochemical synthesis of cupric and cuprous oxides nanoparticles and their optical properties. Ceram. Int. 2013, 39, 8715– 8722,  DOI: 10.1016/j.ceramint.2013.04.055
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    Green sonochemical synthesis of cupric and cuprous oxides nanoparticles and their optical properties
    Shui, Anze; Zhu, Wenli; Xu, Linfeng; Qin, Dong; Wang, Yanmin
    Ceramics International (2013), 39 (8), 8715-8722CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
    Nanoparticles of CuO and Cu2O with various morphologies were prepd. by a green sonochem. process without any surfactants and templates. The Cu2O nanoparticles with the truncated cubic, cubic octahedral, and octahedral morphologies were prepd. via the deoxidn. of the CuO nanoparticles. The Cu2O and CuO samples were characterized by x-ray diffraction (XRD), SEM, and UV visible absorption spectroscopy (UV-vis). The molar ratio of NaOH to copper sulfate affects the morphol. and size of the CuO and Cu2O nanoparticles produced by the sonication. The band gap energy of CuO nanoparticles was 1.45-1.75 eV, the morphol. had a great effect on the optical properties of CuO. The Cu2O nanoparticles had broad emission peaks at the visible region, and the band gap energy was estd. to be 1.95-2.09 eV. The growth mechanisms of the CuO and Cu2O nanoparticles are discussed.
  11. 11
    Jadhav, S.; Gaikwad, S.; Nimse, M.; Rajbhoj, A. Copper Oxide Nanoparticles: Synthesis, Characterization and Their Antibacterial Activity. J. Cluster Sci. 2011, 22, 121– 129,  DOI: 10.1007/s10876-011-0349-7
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    Copper Oxide Nanoparticles: Synthesis, Characterization and Their Antibacterial Activity
    Jadhav, Sunita; Gaikwad, Suresh; Nimse, Madhav; Rajbhoj, Anjali
    Journal of Cluster Science (2011), 22 (2), 121-129CODEN: JCSCEB; ISSN:1040-7278. (Springer)
    Copper oxide nanoparticles were prepd. by electrochem. redn. method using tetra-Bu ammonium bromide (TBAB) as structure directing agent in an org. medium viz. THF and acetonitrile (ACN) in 4:1 ratio by optimizing c.d. and molar concn. of the ligand. The redn. process takes place under inert atm. of nitrogen over a period of 2 h. Such nanoparticles were prepd. using simple electrolysis cell in which the sacrificial anode as a com. available copper metal sheet and platinum (inert) sheet act as a cathode. The parameters such as c.d., solvent polarity, distance between electrodes, and concn. of stabilizers were used to control the size of nanoparticles. The synthesized copper oxide nanoparticles were characterized by using UV-Visible, FTIR, XRD, SEM-EDS and TEM anal. techniques. The nanoparticles were tested for antibacterial activity against human pathogens like Escherichia coli (E. coli) and Staphylococcus strains and which is excellent.
  12. 12
    Borgohain, K.; Murase, N.; Mahamuni, S. Synthesis and properties of Cu2O quantum particles. J. Appl. Phys. 2002, 92, 1292– 1297,  DOI: 10.1063/1.1491020
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    Synthesis and properties of Cu2O quantum particles
    Borgohain, Kavita; Murase, Norio; Mahamuni, Shailaja
    Journal of Applied Physics (2002), 92 (3), 1292-1297CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
    Cuprous oxide quantum particles ≥2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochem. route. Quantum confinement effects are evident from a blueshift in the optical absorption. The optical absorption spectra of Cu2O nanoparticles of different sizes are discussed. Structural anal. by x-ray diffraction as well as electron diffraction shows the nanoparticles to be cubic and single phased Cu2O. x-ray photoelectron spectroscopic studies indicate CuO on the surface of Cu2O core nanoparticles.
  13. 13
    Pandey, P.; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C. Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria. J. Nanopart. Res. 2012, 14, 709  DOI: 10.1007/s11051-011-0709-0
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    Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria
    Pandey, Pratibha; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C.
    Journal of Nanoparticle Research (2012), 14 (1), 709/1-709/13CODEN: JNARFA; ISSN:1388-0764. (Springer)
    Copper (II) oxide multi-armed nanoparticles composed of 500-1000 nm long radiating nanospicules with 100-200 nm width near the base and 50-100 nm width at the tapered ends and ∼25 nm thickness were synthesized by electrochem. deposition in the presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphol. and compn., Raman spectroscopy for compd. identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-pos. and -neg. waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano CuO killed 3 × 108 CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 106 CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, resp. Antibacterial activity of nano CuO has been found many-fold compared with com. bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purifn. and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.
  14. 14
    (a) Dagher, S.; Haik, Y.; Ayesh, A. I.; Tit, N. Synthesis andoptical properties of colloidal CuO nanoparticles. J. Lumin. 2014, 151, 149– 154,  DOI: 10.1016/j.jlumin.2014.02.015
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    14a
    Synthesis and optical properties of colloidal CuO nanoparticles
    Dagher, Sawsan; Haik, Yousef; Ayesh, Ahmad I.; Tit, Nacir
    Journal of Luminescence (2014), 151 (), 149-154CODEN: JLUMA8; ISSN:0022-2313. (Elsevier B.V.)
    Copper oxide nanoparticles of sizes ranging from 1 to 25 nm were synthesized using a colloid microwave-thermal method, where the av. size of CuO nanoparticles can be tailored by controlled microwave treatment time. The particle size was found to significantly decrease as the microwave processing time increases and can be controlled to have narrow size distributions. Both SEM (SEM) and transmission electron microscopy (TEM) were used to characterize the sizes of the prepd. nanoparticles. The UV-visible absorption spectra of the nanoparticles are blue-shifted with the size redn., and this is attributed to quantum-confinement (QC) effect. Furthermore, the photoluminescence spectra showed UV and visible emissions, and were red shifted with increasing particles size and excitation wavelength. While the former observation confirms the QC effect and corroborates the results of UV-visible absorption spectra, the latter one is attributed to selective near band-edge excitonic transitions assocd. with defect states.
    (b) Wang, Y. X.; Tang, X. F.; Yang, Z. G. A novel wet-chemical method of preparing highly monodispersed Cu2O nanoparticles. Colloids Surf., A 2011, 388, 38– 40,  DOI: 10.1016/j.colsurfa.2011.08.004
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    14b
    A novel wet-chemical method of preparing highly monodispersed Cu2O nanoparticles
    Wang, Ying-Xia; Tang, Xiao-Feng; Yang, Zhen-Guo
    Colloids and Surfaces, A: Physicochemical and Engineering Aspects (2011), 388 (1-3), 38-40CODEN: CPEAEH; ISSN:0927-7757. (Elsevier B.V.)
    Highly monodispersed cuprous oxide (Cu2O) nanoparticles, which have a potential application in printed electronics, have been successfully synthesized by a simple wet-chem. route and have been characterized by XRD, HRTEM, UV-vis, and FTIR. The results have shown that the particle size can be controlled by changing the concn. of the stabilizing mol.-oleic acid. Cu2O nanoparticles are spherically shaped with a diam. of about 2 nm and form a face-centered cubic (FCC) crystal structure when the molar ratio of oleic acid to copper precursor is 2. It can be concluded that the Cu2O nanoparticles are capped with oleic acid and polyethylene glycol monododecyl ether. The nano-agglomeration can be filtrated and easily re-dispersed in apolar solvent without ultrasonic method or vigorous stirring.
  15. 15
    (a) Yang, C.; Su, X.; Wang, J.; Cao, X.; Wang, S.; Zhang, L. Facile microwave-assisted hydrothermal synthesis of varied-shaped CuO nanoparticles and their gas sensing properties. Sens. Actuators, B 2013, 185, 159– 165,  DOI: 10.1016/j.snb.2013.04.100
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    15a
    Facile microwave-assisted hydrothermal synthesis of varied-shaped CuO nanoparticles and their gas sensing properties
    Yang, Chao; Su, Xintai; Wang, Jide; Cao, Xudong; Wang, Shoujiang; Zhang, Lu
    Sensors and Actuators, B: Chemical (2013), 185 (), 159-165CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
    CuO nanoparticles of varying shape (tadpole-shaped, spindly, leaf/sphere-like and fusiform) were prepd. by a facile microwave-assisted hydrothermal (MH) method. The products were characterized by x-ray diffraction (XRD), FTIR spectroscopy, and TEM. XRD and TEM results revealed pure phase monoclinic CuO nanoparticles with uniform shapes and sizes. FTIR and UV-vis measurements of these nanoparticles with varying shape showed a highly shape-dependent nature. The gas sensing performance of the obtained nanoparticles was analyzed by detection of target gases, including methanol, ethanol, and acetone at 220°. The tadpole-shaped CuO nanoparticles displayed the best response of ≈5 toward 1000 ppm methanol, ≈7 toward 1000 ppm ethanol, and ≈8 toward 800 ppm acetone, resp. All these CuO-based sensors exhibited a relatively higher response to acetone when compared to their response toward methanol and ethanol. The enhanced sensing performance of the tadpole-shaped CuO sensor may be attributed to their unique shape and small size, which is more favorable in rapid and efficient diffusion of org. vapors than the other shaped CuO nanoparticles.
    (b) Wang, H.; Xu, J. Z.; Zhu, J. J.; Chen, H. Y. Preparation of CuO nanoparticles by microwave irradiation. J. Cryst. Growth 2002, 244, 88– 94,  DOI: 10.1016/S0022-0248(02)01571-3
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    15b
    Preparation of CuO nanoparticles by microwave irradiation
    Wang, Hui; Xu, Jin-Zhong; Zhu, Jun-Jie; Chen, Hong-Yuan
    Journal of Crystal Growth (2002), 244 (1), 88-94CODEN: JCRGAE; ISSN:0022-0248. (Elsevier Science B.V.)
    CuO nanoparticles with an av. size of ∼4 nm have been successfully prepd. by microwave irradn., using copper(II) acetate and sodium hydroxide as the starting materials and ethanol as the solvent. The CuO nanoparticles are characterized by using techniques such as x-ray powder diffraction, transmission electron microscopy, selected area electron diffraction, XPS and UV-visible absorption spectroscopy. The as-prepd. CuO nanoparticles have regular shape, narrow size distribution and high purity. The band gap is estd. to be 2.43 eV according to the results of the optical measurements of the CuO nanoparticles.
  16. 16
    Sahooli, M.; Sabbaghi, S.; Saboori, R. Synthesis and characterization of mono sized CuO nanoparticles. Mater. Lett. 2012, 81, 169– 172,  DOI: 10.1016/j.matlet.2012.04.148
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    Synthesis and characterization of mono-sized CuO nanoparticles
    Sahooli, M.; Sabbaghi, S.; Saboori, R.
    Materials Letters (2012), 81 (), 169-172CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    In this piece of research we have used pptn. method to synthesize CuO nanoparticles. To investigate the characteristics of the CuO nanoparticles, particle size analyzer (PSA), X-ray diffraction technique (XRD), SEM (SEM) and UV-visible absorption spectroscopy were used. To produce nanoparticles with uniform size, we optimized exptl. conditions such as the temp. which was set at 78 °C. The results showed that the synthesized CuO nanoparticles have a suitable dispersion and a thin-size distribution. Also based on the results, the av. size of the nanoparticles was about 4 nm, CuO nanoparticles with various shapes such as clews-like, nanowire, and stretched nanowire-shaped were synthesized by different reaction temps. along with controlled addn. of NaOH, and the surface area was obtained by the BET adsorption method. The max. surface area obtained was 143.7 m2/g which is a considerable surface area.
  17. 17
    (a) Rangel, W. M.; Antunes, R. A.; Gracher, H. A facile method for synthesis of nanostructured copper (II) oxide by coprecipitation. J Mater Res. Technol. 2020, 9, 994– 1004,  DOI: 10.1016/j.jmrt.2019.11.039
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    17a
    A facile method for synthesis of nanostructured copper (II) oxide by coprecipitation
    Rangel, Wellington Marques; Boca Santa, Rozineide A. Antunes; Riella, Humberto Gracher
    Journal of Materials Research and Technology (2020), 9 (1), 994-1004CODEN: JMRTAL; ISSN:2238-7854. (Elsevier B.V.)
    Due to their versatility e wide range of phys. and chem. properties, transition metal oxides are very promising as nanostructured materials. Copper oxides are indicated for applications in increasingly wider areas as gas sensing, catalysts, solar cells, electrochromic devices, and antimicrobial materials. In this study, copper (II) oxide nanoparticles were synthesized by the copptn. method from two precursors: copper sulfate and copper chloride. The evaluated precursor concns. were 0.1 M and 0.2 M and temps. were 50 °C and 75 °C. Different results were found, according to synthesis parameters and precursor used. Using copper sulfate as a precursor, a single phase of polycryst. CuO could be obtained, and only a mixt. of cryst. phases of CuO and cllinoatacamite (Cu2(OH)3Cl) were found using copper chloride as the precursor. A known polymorphism phenomenon was obsd. in clinoatacamite according to synthesis reaction parameters, and all three polymorphs were found mixed with CuO nanoparticles. Crystallite sizes of about 10 nm were found in this study, with leaf and rod-like nanostructured particles with dimensions range from 190 to 700 nm, and very good thermal stability. Under the synthesis conditions selected in this study, nanostructured materials made with copper sulfate precursor exhibited smaller crystallite sizes and better thermal stability. The copptn. method used was considered adequate to obtain nanostructured materials, with the advantages of being simple, fast and inexpensive.
    (b) Phiwdang, K.; Suphankij, S.; Mekprasart, W.; Pecharapa, W. Synthesis of CuO Nanoparticles by Precipitation Method Using Different Precursors. Energy Procedia 2013, 34, 740– 745,  DOI: 10.1016/j.egypro.2013.06.808
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    Synthesis of CuO nanoparticles by precipitation method using different precursors
    Phiwdang, Kankanit; Suphankij, Sineenart; Mekprasart, Wanichaya; Pecharapa, Wisanu
    Energy Procedia (2013), 34 (), 740-745CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
    CuO nanoparticles were synthesized by pptn. method using different precursors as copper nitrate (Cu(NO3)2) and copper chloride (CuCl2) with post-heating comparing between as-synthesized and after calcinations. Relevant properties of as-synthesized nanoparticles were investigated by x-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier Transform IR (FTIR) Spectroscopy. Overall results suggest that the formation of CuO nanostructures with different shape, size and morphol. can be achieved using different precursors via this process. The improvement in their crystallinity and purifn. can be further attained by post calcinations process.
    (c) El-Trass, A.; El-Shamy, H.; El-Mehasseb, I.; El-Kema, M. CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids. Appl. Surf. Sci. 2012, 258, 2997– 3001,  DOI: 10.1016/j.apsusc.2011.11.025
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    CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids
    El-Trass, A.; El Shamy, H.; El-Mehasseb, I.; El-Kemary, M.
    Applied Surface Science (2012), 258 (7), 2997-3001CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
    CuO nanoparticles with an av. size of 6 nm were prepd. by an alcothermal method. The prepd. CuO nanoparticles were characterized by x-ray diffraction, TEM, FTIR, and UV-visible absorption spectroscopy. A strong sharp emission under UV excitation is reported from the prepd. CuO nanoparticles. The CuO nanoparticles have high dispersion and narrow size distribution. The fluorescence emission spectra display an intense sharp emission at 365 nm and weak broad intensity emission at 470 nm. Picosecond fluorescence measurements of the nanoparticles suggest bi-exponential function giving time consts. of τ1 (330 ps, 94.21%) and τ 2 (4.69 ns, 5.79%). In neutral and alk. solns., zeta potential values of CuO nanoparticles are neg., due to the adsorption of COO- group via the coordination of bidentate. At low pH the zeta potential value is pos. due to the increased potential of H+ ions in soln. Comparative UV-visible absorption expts. with the model amino acid compds. of pos. and neg. charges as arginine and aspartic acid, resp. confirmed the neg. surface of CuO nanoparticles. The results should be extremely useful for understanding the mode of the interaction with biol. systems. This binding process also affects the particle behavior inside the body.
    (d) Pike, J.; Chan, F. S. W.; Zhang, F.; Wang, X.; Hanson, J. Formation of stable Cu2O from reduction of CuO nanoparticles. Appl. Catal., A 2006, 303, 273– 277,  DOI: 10.1016/j.apcata.2006.02.008
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    Formation of stable Cu2O from reduction of CuO nanoparticles
    Pike, Jenna; Chan, Siu-Wai; Zhang, Feng; Wang, Xianqin; Hanson, Jonathan
    Applied Catalysis, A: General (2006), 303 (2), 273-277CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
    In situ time-resolved X-ray diffraction (TR-XRD) using synchrotron radiation has been used to capture the dynamics of the redn. of nanocryst. CuO using a normal supply of CO gas. Copper(II) oxide nanoparticles 4-16 nm in width, as measured by XRD peak broadening, are synthesized using an aq. org.-nitrate method and reduced in isothermal and temp. ramping redn. expts. Temp.-programmed redn. of CuO nanoparticles using a ramping heating profile was obsd. to result in the sequential redn. process CuO → Cu2O → Cu, with CuO reducing completely to the intermediate Cu2O phase before further redn. to metallic copper. Isothermal redn. expts. at 250 °C show that CuO nanoparticles completely reduce to Cu2O, and this phase remains stable without further redn. with continued exposure to CO. In contrast to what is typically obsd. in bulk CuO in both isothermal and ramping redn. conditions, nanocryst. CuO reduces to a stable Cu2O phase rather than forming metallic copper directly. The behavior of the CuO nanoparticles in temp. ramping reducing conditions is controlled by the particle size, with the smaller CuO nanoparticles exhibiting a greater stability and withstanding a higher temp. before their redn. to Cu2O and then to metallic copper nanoparticles.
    (e) Zhu, J.; Li, D.; Chen, H.; Yang, X.; Lu, L.; Wan, X. Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method. Mater. Lett. 2004, 58, 3324– 3327,  DOI: 10.1016/j.matlet.2004.06.031
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    Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method
    Zhu, Junwu; Li, Dan; Chen, Haiqun; Yang, Xujie; Lu, Lude; Wang, Xin
    Materials Letters (2004), 58 (26), 3324-3327CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    Highly dispersed CuO nanoparticles with an av. size of 6 nm were prepd. by a novel quick-pptn. method. The as-prepd. CuO nanoparticles were characterized by x-ray diffraction, TEM, UV-visible absorption spectroscopy, and BET nitrogen adsorption. The as-prepd. CuO nanoparticles have high dispersion and narrow size distribution. The influence of reaction conditions on morphol. of CuO nanocrystals was discussed. Spherical, ellipsoidal, and needle-shaped CuO nanocrystals can be obtained simply by varying the reaction temp. and controlling the addn. of NaOH.
  18. 18
    Yagi, S. Potential-pH Diagrams for Oxidation-State Control of Nanoparticles Synthesized via Chemical Reduction. In Thermodynamics - Physical Chemistry of Aqueous Systems; Moreno-Piraján, J. S., Ed.; InTech: London, 2011; pp 223– 239.
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    Arshadi-Rastabi, S.; Moghaddam, J.; Reza, M. Synthesis, characterization and stability of Cu2O nanoparticles produced via supersaturation method considering operational parameters effect. J. Ind. Eng. Chem. 2015, 22, 34– 40,  DOI: 10.1016/j.jiec.2014.06.022
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    Synthesis, characterization and stability of Cu2O nanoparticles produced via supersaturation method considering operational parameters effect
    Arshadi-Rastabi, Shahrzad; Moghaddam, Javad; Reza Eskandarian, Mohammad
    Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2015), 22 (), 34-40CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
    Cuprous oxide (Cu2O) nanoparticles have been successfully synthesized using copper acetate as precursor via supersatn. theory as a facile rout. Synthesis parameters, such as the reducing agent concn., reaction temp., reaction time, type of the reducing agent and rate of adding reducing agent were investigated. The exptl. results indicated that size of the Cu2O nanoparticles is dependent on the above mentioned parameters. The Cu2O samples were characterized by X-ray diffraction (XRD), SEM and also by ultra violet visible spectroscopy (UV-vis). Results showed that temp. has unique influence on to the fabrication of Cu2O nanoparticles which illustrate the higher the temp. of the synthesis the smaller the particles would be. Rate of redn. was specified as an influential factor in detg. the particle size distribution. Particles with crystallite size of 74.01 nm were obtained among this study.
  20. 20
    Dodoo-Arhin, D.; Leoni, M.; Scardi, P.; Garnier, E.; Mittiga, A. Synthesis, characterisation and stability of Cu2O nanoparticles produced via reverse micelles microemulsion. Mater. Chem. Phys. 2010, 122, 602– 608,  DOI: 10.1016/j.matchemphys.2010.03.053
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    Synthesis, characterisation and stability of Cu2O nanoparticles produced via reverse micelles microemulsion
    Dodoo-Arhin, D.; Leoni, M.; Scardi, P.; Garnier, E.; Mittiga, A.
    Materials Chemistry and Physics (2010), 122 (2-3), 602-608CODEN: MCHPDR; ISSN:0254-0584. (Elsevier B.V.)
    Cuprite (Cu2O) nanoparticles were synthesized at room temp. via redn. of CuCl2·2H2O by NaBH4 in water/n-heptane microemulsion stabilized by the non-ionic Brij30 surfactant. Whole Powder Pattern Modeling of the X-ray diffraction patterns shows the presence of a bimodal size distribution in the nanopowders, with a fraction of domains in the 10-40 nm range and a smaller one below 10 nm. Linear and planar defects are absent. A relationship between the av. size of the larger particles and the quantity of water in the system was obtained. The stability of cuprite under visible light irradn. both during the synthesis and after the prepn. was investigated, showing that a self-catalytic conversion of Cu2O into CuO takes place in water.
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    Fan, G.; Li, F. Effect of sodium borohydride on growth process of controlled flower-like nanostructured Cu2O/CuO films and their hydrophobic property. Chem. Eng. J. 2011, 167, 388– 396,  DOI: 10.1016/j.cej.2010.12.090
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    Effect of sodium borohydride on growth process of controlled flower-like nanostructured Cu2O/CuO films and their hydrophobic property
    Fan, Guoli; Li, Feng
    Chemical Engineering Journal (Amsterdam, Netherlands) (2011), 167 (1), 388-396CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    In this paper, we report on the three-dimensional nanostructured Cu2O/CuO films with controlled flower-like shapes using a direct crystn. approach in the presence of sodium borohydride without using any performed template, surfactant or oxidant. The microstructures and shapes of Cu2O/CuO architectures were investigated by field emission SEM, X-ray diffraction and transmission electron microscopy. Three types of chrysanthemum-like, candock-like and dandelion-like CuO microstructures consisting of densely packed building blocks of nanobelts or nanoribbons were achieved by governing the concns. of NaBH4. Possible growth mechanisms for the controlled organization of primary building units into three-dimensional flower-like architectures were proposed. After simple surface modification with sodium laurate, the resulting films displayed hydrophobic and even superhydrophobic properties owing to their special surface nano-/microstructures.
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    (a) Yuan, L.; Yin, Q.; Wang, Y.; Zhou, G. CuO reduction induced formation of CuO/Cu2O hybrid oxides. Chem. Phys. Lett. 2013, 590, 92– 96,  DOI: 10.1016/j.cplett.2013.10.040
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    CuO reduction induced formation of CuO/Cu2O hybrid oxides
    Yuan, Lu; Yin, Qiyue; Wang, Yiqian; Zhou, Guangwen
    Chemical Physics Letters (2013), 590 (), 92-96CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
    Redn. of CuO nanowires results in the formation of a unique hierarchical hybrid nanostructure, in which the parent oxide phase (CuO) works as the skeleton while the lower oxide (Cu2O) resulting from the redn. reaction forms as partially embedded nanoparticles that decorate the skeleton of the parent oxide. Using in situ transmission electron microscopy observations of the redn. process of CuO nanowires, we demonstrate that the formation of such a hierarchical hybrid oxide structure is induced by topotactic nucleation and growth of Cu2O islands on the parent CuO nanowires.
    (b) Srivastava, M.; Singh, J.; Mishra, R. K.; Ojha, A. K. Electro-optical and magnetic properties of monodispersed colloidal Cu2O nanoparticles. J. Alloys Compd. 2013, 555, 123– 130,  DOI: 10.1016/j.jallcom.2012.12.049
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    A facile synthesis of colloidal cuprous oxide (Cu2O) nanoparticles was reported via co-pptn. route. Cryst. structure/phase identification, surface morphol., particles size/shape were studied through x-ray diffraction, SEM and TEM techniques, resp. Transmission electron microscope studies reveal that the synthesized nanoparticles are uniform and having spherical shape with av. size of ∼6 nm. The optical properties were probed through FTIR spectroscopy, Raman spectroscopy and UV-visible spectroscopy. Energy band gap studies of the Cu2O nanoparticles reveal the possibility of both, direct and indirect optical transitions. Magnetic properties of the synthesized nanoparticle were measured through vibrating sample magnetometer technique and the obtained result shows that the synthesized nanoparticles possess weak ferromagnetic nature at room temp. Electrochem. response studies of Cu2O/In Sn oxide electrode were carried out using cyclic voltammetry and electrochem. impedance spectroscopy. The electrode prepd. using the colloidal Cu2O nanoparticle shows excellent selectivity and sensitivity for these measurements, which can further be used for an efficient electrochem. based biosensor applications.
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    Han, D.; Yang, H.; Zhu, C.; Wang, F. Controlled synthesis of CuO nanoparticles using TritonX-100-based water-in-oil reverse micelles. Powder Technol. 2008, 185, 286– 290,  DOI: 10.1016/j.powtec.2007.10.018
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    Controlled synthesis of CuO nanoparticles using TritonX-100-based water-in-oil reverse micelles
    Han, Dongyun; Yang, Huaiyu; Zhu, Chengyun; Wang, Fuhui
    Powder Technology (2008), 185 (3), 286-290CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
    CuO nanoparticles were synthesized by TritonX-100 based water-in-oil reverse micelles system, and characterized by x-ray diffractometer (XRD) and TEM, resp. The grain size, morphol., and distribution were highly dependent on the ratio of water to surfactant (R). The control effect of water content dissolved in reverse micelles was attributed to the enhancement of the exchange rate of reactants among micelles and the relevant change in the interfacial film flexibility of reverse micelles with the increasing amt. of water in the microemulsion.
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    Etefagh, R.; Azhir, E.; Shahtahmasebi, N. Synthesis of CuO nanoparticles and fabrication of nanostructural layer biosensors for detecting Aspergillus niger fungi. Sci. Iran. 2013, 20, 1055– 1058,  DOI: 10.1016/j.scient.2013.05.015
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    Liu, X.; Geng, B.; Du, Q.; Ma, J.; Liu, X. Temperature-controlled self-assembled synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route. Mater. Sci. Eng., A 2007, 448, 7– 14,  DOI: 10.1016/j.msea.2006.08.104
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    Temperature-controlled self-assembled synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route
    Liu, Xiaowang; Geng, Baoyou; Du, Qingbo; Ma, Jinzhu; Liu, Xianming
    Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing (2007), A448 (1-2), 7-14CODEN: MSAPE3; ISSN:0921-5093. (Elsevier B.V.)
    In this paper, we report on the synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route by controlling the growth temp. CuO and Cu2O nanoparticles have nanoporous structural configurations composed of a large no. of primary particles. According to the difference between the crystal planes, we proposed the possible growth mechanisms of CuO, Cu2O and Cu nanoparticles. Selective adsorption of oleylamine on various crystal planes may play an important role in the growth process. The understanding of this self-assembling process will help us to develop reliable and reproducible methods to synthesis other three dimensional nanostructured architectures and increase the knowledge of self-assembly.
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    Lee, W.; Piao, L.; Park, C.; Lim, Y.; Do, Y.; Yoon, S.; Kim, S.-H. Facile synthesis and size control of spherical aggregates composed of Cu2O nanoparticles. J. Colloid Interface Sci. 2010, 342, 198– 201,  DOI: 10.1016/j.jcis.2009.10.027
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    Facile synthesis and size control of spherical aggregates composed of Cu(2)O nanoparticles
    Lee Woo-Ram; Piao Longhai; Park Cheol-Hee; Lim Young Soo; Do Young Rag; Yoon Sungho; Kim Sang-Ho
    Journal of colloid and interface science (2010), 342 (1), 198-201 ISSN:.
    The secondary structures of Cu(2)O nanoparticles were prepared in aqueous solution utilizing self-assembled aggregation process. By introducing polyacrylamide (PAM) as a secondary surfactant, the colloidal nanoparticle aggregates (CNAs) become uniform in size and exhibit spherical shape compared to the random aggregates without PAM. The size of CNA can be systematically controlled from 300nm to 1000nm by varying PAM concentration. The formation mechanism was explained based on a conventional colloidal particle formation mechanism. These control methods may generally be applied to the preparation of secondary nanoparticle structures.
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    (a) Siddiqi, K. S.; Husen, A. Current status of plant metabolite-based fabrication of copper/copper oxide nanoparticles and their applications: a review. Biomater. Res. 2020, 24, 11  DOI: 10.1186/s40824-020-00188-1
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    Current status of plant metabolite-based fabrication of copper/copper oxide nanoparticles and their applications: a review
    Siddiqi, Khwaja Salahuddin; Husen, Azamal
    Biomaterials Research (2020), 24 (1), 11CODEN: BRIEFJ; ISSN:2055-7124. (BioMed Central Ltd.)
    A review. Abstr.: Since green mode of nanoparticles (NPs) synthesis is simple, advantageous and environment friendly relative to chem. and phys. procedures, various plant species have been used to fabricate copper and copper oxide nanoparticles (Cu/CuO-NPs) owing to the presence of phytochems. which often act as capping as well as stabilizing agent. These Cu/CuO-NPs are highly stable and used in the degrdn. of org. dyes like methylene blue and redn. of org. compds. such as phenols. They are also used as antibacterial, antioxidant and antifungal agent due to their cytotoxicity. They are also examd. for agricultural crops growth and productivity. Cu-NPs increased the root and shoot growth of mung bean. In wheat plants, these particles reduced shoot growth; and enhanced the grain yield and stress tolerance through starch degrdn. Similarly, CuO-NPs treated seedlings have shown reduced chlorophyll, carotenoid and sugar content, whereas proline and anthocyanins were increased in Brassica rapa seedlings. Overall, this review presents the recent understanding of plant-mediated Cu and CuO-NPs fabrication and their application in biomedicine, environmental remediation and agricultural practices. A comparison of the traditional/conventional method of fabrication of NPs with those of green protocols has also been made. Some misconception of copper chem. has also been critically discussed in terms of oxidn. and redn. reactions.
    (b) Ananda, H. C.; Desalegn, T.; Kassa, M.; Abebe, B.; Assefa, T. Synthesis of Green Copper Nanoparticles Using Medicinal Plant Hagenia abyssinica (Brace) JF. Gmel. Leaf Extract: Antimicrobial Properties. J. Nanomater. 2020, 1– 12,  DOI: 10.1155/2020/3924081
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    Green and traditional synthesis of copper oxide nanoparticles-comparative study
    Keabadile, Obakeng P.; Aremu, Adeyemi O.; Elugoke, Saheed E.; Fayemi, Omolola E.
    Nanomaterials (2020), 10 (12), 2502CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
    The current study compared the synthesis, characterization and properties of copper oxide nanoparticles (CuO) based on green and traditional chem. methods. The synthesized CuO were confirmed by spectroscopic and morphol. characterization such as UV-visible (UV-vis) spectroscopy, fourier transform IR (FTIR) spectroscopy, zeta potential, SEM (SEM) and energy dispersed X-ray (EDX). Electrochem. behavior of the modified electrodes was done using cyclic voltammetry (CV) in ferricyanide/ferrocyanide ([Fe(CN)6]4-/[Fe(CN)6]3-) redox probe. As revealed by UV spectrophotometer, the absorption peaks ranged from 290-293 nm for all synthesized nanoparticles. Based on SEM images, CuO were spherical in shape with agglomerated particles. Zeta potential revealed that the green CuO have more neg. surface charge than the chem. synthesized CuO. The potential of the green synthesized nanoparticles was higher relative to the chem. synthesized one. Cyclic voltammetry studies indicated that the traditional chem. synthesized CuO and the green CuO have electrocatalytic activity toward the ferricyanide redox probe. This suggests that the green CuO can be modified with other nanomaterials for the prepn. of electrochem. sensors toward analytes of interest.
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    Ganga, B. G.; Santhosh, P. N. Manipulating aggregation of CuO nanoparticles: Correlation between morphology and optical properties. J. Alloys Compd. 2014, 612, 456– 464,  DOI: 10.1016/j.jallcom.2014.05.171
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    Manipulating aggregation of CuO nanoparticles: Correlation between morphology and optical properties
    Ganga, B. G.; Santhosh, P. N.
    Journal of Alloys and Compounds (2014), 612 (), 456-464CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    Controlled synthesis of CuO nanoparticles with various morphologies were achieved by a wet chem. method by the redn. of copper acetate with NaOH. Influence of surfactant, alk. concn. and solvent medium on the morphol. of nanoparticles was investigated. Our studies reveal that these parameters alter the aggregation-growth processes and hence the morphol. Sodium dodecyl sulfate (SDS) as a structure-guiding agent has a strong impact on the morphol. of nanostructure. By adjusting the rate of hydrolysis, two dimensional netted structures consisting of bundles of nanorods were obtained, formed by oriented attachment mechanism. Moreover, well defined and dispersed CuO nanoparticles were produced by manipulating the solvent medium. Optical properties were studied using UV-Vis absorption and Raman spectroscopy. Morphol. and size of nanoparticles have a profound effect on the nature of multi-phonon band obsd. in the Raman spectra of CuO nanostructures.
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    Rao, M. P.; Anandan, S.; Suresh, S.; Asiri, A. M.; Wu, J. J. Surfactant Assisted Synthesis of Copper Oxide Nanoparticles for Photocatalytic Degradation of Methylene Blue in the Presence of Visible Light. Energy Environ. Focus 2015, 4, 250– 255,  DOI: 10.1166/eef.2015.1168
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    Reddy, S.; Kumara Swamy, B. E.; Jayadevappa, H. CuO nanoparticle sensor for the electrochemical determination of dopamine. Electrochim. Acta 2012, 61, 78– 86,  DOI: 10.1016/j.electacta.2011.11.091
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    CuO nanoparticle sensor for the electrochemical determination of dopamine
    Reddy, Sathish; Kumara Swamy, B. E.; Jayadevappa, H.
    Electrochimica Acta (2012), 61 (), 78-86CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
    Different shaped CuO nanoparticles were synthesized using cetyl tri-Me ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) in a co-pptn. method. The CuO nanoparticles were characterized using XRD, SEM, TEM, IR absorption spectroscopy (IR) and UV-visible absorption spectroscopy (UV-visible). The prepd. CuO nanoparticles were used for the prepn. of modified carbon-paste electrodes (MCPE) for the electrochem. detection of dopamine (DA) at pH 6.0. The MCPE prepd. from flake-shaped CuO nanoparticles exhibited an enhanced current response for DA. Electrochem. parameters, such as the surface area of the electrode, the heterogeneous rate const. (ks) and the lower detection limit (5.5 × 10-8 M), were calcd. and compared with those of the MCPE prepd. from rod-shaped CuO nanoparticles. The MCPE prepd. from SDS/polyglycine/flake-shaped CuO nanoparticles exhibited a further improved current response for DA and a high selectivity (E AA - E DA = 0.28 V) for the simultaneous study of DA and ascorbic acid (AA) at pH 6.0. The modified carbon-paste electrochem. sensors were compared, and the MCPE prepd. from SDS/polyglycine/flake-shaped CuO nanoparticles exhibited better performance than the MCPE prepd. from CTAB/polyglycine/flake-shaped CuO nanoparticles.
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    Namburu, P. K.; Kulkarni, D. P.; Misra, D.; Das, D. K. Viscosity of copper oxide nanoparticles dispersed in ethylene glycol and water mixture. Exp. Therm. Fluid Sci. 2007, 32, 397– 402,  DOI: 10.1016/j.expthermflusci.2007.05.001
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    Viscosity of copper oxide nanoparticles dispersed in ethylene glycol and water mixture
    Namburu, Praveen K.; Kulkarni, Devdatta P.; Misra, Debasmita; Das, Debendra K.
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    Nanofluids are new kinds of fluids engineered by dispersing nanoparticles in base fluids. This paper presents an exptl. investigation of rheol. properties of copper oxide nanoparticles suspended in 60:40 (by wt.) ethylene glycol and water mixt. Nanofluids of particle vol. percentage ranging from 0% to 6.12% were tested. The expts. were carried over temps. ranging from -35 °C to 50 °C to demonstrate their applicability in cold regions. For the particle vol. concns. tested, nanofluids exhibited Newtonian behavior. An exptl. correlation was developed based on the data, which relates viscosity with particle vol. percent and the nanofluid temp.
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    Siddiqui, H.; Qureshi, M. S.; Haque, F. Z. Preparation of silver nanoparticles by laser ablation in polyvinylpyrrolidone solutions nanostructures and their spectroscopic analysis. Optik 2016, 127, 2740– 2747,  DOI: 10.1016/j.ijleo.2015.11.220
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    Surfactant assisted wet chemical synthesis of copper oxide (CuO) nanostructures and their spectroscopic analysis
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    Optik (Munich, Germany) (2016), 127 (5), 2740-2747CODEN: OTIKAJ; ISSN:0030-4026. (Elsevier GmbH)
    CuO nanocrystals and their nanoarchitectures with various morphologies were constructed via a simple surfactant-assisted wet chem. process. The introduction of sodium dodecyl sulfate (SDS) as anionic surfactant, cetyltrimethylammonium bromide (CTAB) as cationic surfactant and polyethylene glycol (PEG) as nonionic surfactant leads to the formation of cube, leaf and flower-like CuO nanostructures, resp. The prepd. samples were characterized by different characterization techniques such as X-ray diffraction (XRD), SEM (SEM), Fourier transform IR (FT-IR) spectroscopy, Raman, UV-visible diffused reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. Different spectroscopic results revealed that all the samples have cryst. single-phase CuO monoclinic structures. The av. crystallite size for SDS, PEG and CTAB assisted CuO samples are around 20 nm, 19 nm and 16 nm resp. It was obsd. that the size and shape of particle is affected by the nature of surfactant. Addnl., in all the samples, Raman and FTIR spectra shows three identical Cu-O vibration modes that indicate the presence of cryst. CuO monoclinic structure. Diffuse reflectance results revealed that the addn. of surfactants significantly enhanced the optical bandgap value from 1.40 eV to 1.54 eV, due to quantum confinement effect. Photoluminescence (PL) spectra showed both UV as well as visible emission peaks indicating their good optical properties. The presence of strong visible light absorption in all the samples revealed that it can be used as absorbing material in solar cell.
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    Mayekar, J.; Dhar, V.; Radha, S. Synthesis of Copper Oxide Nanoparticles Using Simple Chemical Route. Int. J. Sci. Eng. Res. 2014, 5, 928– 930
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    Zhang, H.; Ren, X.; Chi, Z. (2007) Shape-controlled synthesis of Cu2O nanocrystals assisted by PVP and application as catalyst for synthesis of carbon nanofibers. J. Cryst. Growth 2007, 304, 206– 210,  DOI: 10.1016/j.jcrysgro.2007.01.043
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    Shape-controlled synthesis of Cu2O nanocrystals assisted by PVP and application as catalyst for synthesis of carbon nanofibers
    Zhang, Hui; Ren, Xue; Cui, Zuolin
    Journal of Crystal Growth (2007), 304 (1), 206-210CODEN: JCRGAE; ISSN:0022-0248. (Elsevier B.V.)
    In this paper, cuprous oxide (Cu2O) nanostructures with different shapes, such as spheres, cubes and rods, have been synthesized by reducing copper nitrate trihydrate with ethylene glycol in the present of poly(vinylpyrrolidone) (PVP). The molar ratio of PVP (in the repeating unit)/Cu(NO3)2·3H2O and reaction temp. have significant effects on the formation and growth of these Cu2O nanostructures. The Cu2O nanorods were fabricated at the molar ratios of PVP/Cu(NO3)2·3H2O 2-3, while spherical and cubic nanoparticles were formed at the ratios of PVP/Cu(NO3)2·3H2O 5-7 and 10-15. Increasing with reaction temps., monodisperse particles were obtained. The as-synthesized nanoparticles and nanorods were investigated by transmission electron microscopy (TEM), and field emission SEM (FE-SEM) and X-ray diffractometry (XRD). With the as-prepd. nanoparticles as catalyst, carbon nanofibers (CNFs) were synthesized by catalytic polymn. of acetylene at a lower temp. (250 °C). The effects of the catalyst particle sizes on the morphologies of the carbon fibers were studied.
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    Liu, P.; Li, Z.; Cai, W.; Fang, M.; Luo, X. Fabrication of cuprous oxide nanoparticles by laser ablation in PVP aqueous solution. RSC Adv. 2011, 1, 847– 851,  DOI: 10.1039/c1ra00261a
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    Fabrication of cuprous oxide nanoparticles by laser ablation in PVP aqueous solution
    Liu, Peisheng; Li, Zhigang; Cai, Weiping; Fang, Ming; Luo, Xiangdong
    RSC Advances (2011), 1 (5), 847-851CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    The cuprous oxide nanoparticles have been fabricated through pulsed laser ablation of copper target in PVP aq. soln. The structure, morphol. and compn. of the nanoparticles have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resoln. TEM (HRTEM), XPS and X-ray excited auger spectra (XAES). The results show that the mean size of the as-prepd. in diam. is about 29 nm with a relative narrow size distribution and samples are polycrystal Cu2O nanoparticles with a shell of thin layer of amorphous CuO. Furthermore, a possible mechanism for formation of such the cuprous oxide nanoparticles is discussed. We concluded that pulsed laser ablation of copper in liq. is a feasible method for the synthesis of cuprous oxide nanoparticles.
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    Qiang, A.-H.; Zhao, L.-M.; Xu, C.-J.; Zhou, M. Effect of Dispersant on the Colloidal Stability of Nano-sized CuO Suspension. J. Dispersion Sci. Technol. 2007, 28, 1004– 1007,  DOI: 10.1080/01932690701522293
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    Effect of dispersant on the colloidal stability of nano-sized CuO suspension
    Qiang, Ai-Hong; Zhao, Li-Ming; Xu, Chun-Jian; Zhou, Ming
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    The stabilization of nanosized CuO suspensions was examd. to look for the primary mechanism of dispersion. The dispersion stability of suspension was characterized by sedimentation tests, zeta potential, granularity tests, and IR spectroscopy (IR). Influence factors such as pH and the concn. of the dispersant on the colloidal stability of the suspension were investigated. Sodium polyacrylate was fit to stabilize the suspension of CuO nanoparticles through electrosteric repulsion. Also, smaller viscosity and better dispersion effects were achieved when sodium polyacrylate mass fraction was 0.4-0.8% (based on the powder), pH was 10.
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    (a) Liu, Q. M.; Zhou, D. B.; Yamamoto, Y.; Ichino, R.; Okido, M. Preparation of Cu nanoparticles with NaBH4 by aqueous reduction method. Trans. Nonferrous Met. Soc. China 2012, 22, 117– 12,  DOI: 10.1016/S1003-6326(11)61149-7
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    Preparation of Cu nanoparticles with NaBH4 by aqueous reduction method
    Liu, Qing-ming; Zhou, De-bi; Yuya, Yamamoto; Ryoichi, Ichino; Masazumi, Okido
    Transactions of Nonferrous Metals Society of China (2012), 22 (1), 117-123CODEN: TNMCEW; ISSN:1003-6326. (Elsevier B.V.)
    Cu nanoparticles were prepd. by reducing Cu2+ ions with NaBH4 in alk. soln. The effects of NaBH4 concn. and dripping rate on the formation of Cu nanoparticles were studied. The optimum conditions are found to be 0.2 mol/L Cu2+, soln. with pH = 12, temp. of 313 K and 1% gelatin as dispersant, to which 0.4 mol/L NaBH4 is added at a dripping rate of 50 mL/min. NH3 · H2O is found to be the optimal complexant to form the Cu precursor. A series expts. were conducted to study the reaction process at different time points.
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    Copper nanoclusters: Synthesis, characterization and properties
    Lu, Yi Zhong; Wei, Wen Tao; Chen, Wei
    Chinese Science Bulletin (2012), 57 (1), 41-47CODEN: CSBUEF; ISSN:1001-6538. (Springer)
    A review. Metal nanoclusters with a core size smaller than 2 nm have attracted much attention because of their unique phys. and chem. properties. Among the studied metal nanoclusters, gold and silver have been studied extensively by size-controlled synthesis, structural characterization and properties investigations. Recently, considerable research effort has been devoted to the investigation of copper nanoclusters. In this review, we highlight recent progress in the study of copper nanoclusters in terms of synthesis methods, characterization techniques and their novel optical and catalytic properties.
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    Zhao, H.; Yang, J.; Wang, L.; Tian, C.; Jiangaand, B.; Fu, H. Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid. Chem. Commun. 2011, 47, 2014– 2016,  DOI: 10.1039/c0cc04432f
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    Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid
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    Chemical Communications (Cambridge, United Kingdom) (2011), 47 (7), 2014-2016CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Small and highly dispersed Pd nanoparticles supported on graphene nanosheets were fabricated via a strategy of etching a Cu template with Pd2+. The obtained hybrid exhibited significant catalytic activity for formic acid oxidn.
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    (a) Fanning, J. C.; Brooks, B. C.; Hoeglund, A. B.; Pelletier, D. A.; Wadford, J. A. The reduction of nitrate and nitrite ions in basic solution with sodium borohydride in the presence of copper(II) ions. Inorg. Chim. Acta 2000, 310, 115– 119,  DOI: 10.1016/S0020-1693(00)00262-0
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    The reduction of nitrate and nitrite ions in basic solution with sodium borohydride in the presence of copper(II) ions
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    The reaction of NaNO3 and NaBH4 with added Cu(OH)2 in 1 M NaOH at 65° under Ar rapidly produced NH3, Cu metal, and H2 with NO2- formed as an intermediate. The overall equation describing the reaction is: Cu(OH)2 + 3NO3- + 7BH4- + 20H2O → Cu + 3NH3 + 7B(OH)4- + 15H2 + 3OH-. A direct reaction of NaNO2 with NaBH4 under the same conditions as those used with NaNO3 follows the equation: Cu(OH)2 + NO2- + 2BH4- + 5H2O → Cu + 4H2 + NH3 + 2B(OH)4- + OH-. The redns. of nitrate and nitrite with NaBH4 did not take place in basic soln. unless Cu(OH)2 was present. The NO3-/BH4- reaction was studied in basic medium since nuclear waste is basic (pH ≈ 14), and since NaBH4 is safely handled and stored in basic soln. Also, having borate ion, a potential glass-former, as a product in the elimination of nitrate from waste would be an advantage.
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    Cobalt(II) removal from water by chemical reduction with sodium borohydride
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    Water Research (1993), 27 (6), 985-92CODEN: WATRAG; ISSN:0043-1354.
    The stoichiometry and kinetics of Co2+ redn. with NaBH4 in aq. soln. were studied. An excess of borohydride is needed to complete Co2+ removal from wastewater. In this case, Co ppts. mainly as Co(OH)2. Absence of dissolved O in the reactor is required to avoid rapid reoxidn. of reduced Co. The elemental anal. of the reduced species is consistent with Co2B. The ease of sludge reoxidn. and the final B concn. in the effluent resulting from the needed borohydride excess are serious disadvantages of this technique to remove Co2+. A kinetic model was proposed to describe the behavior of the system. The model reproduces reasonably well exptl. results, although some discrepancies were obsd. in the early stages of the process. These can be mainly attributed to mass-transfer limitations.
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    Burriel, F.; Lucena, F.; Arribas, S.; Hernández, J. Reacciones de oxido-reducción. In Química Analítica Cuantitativa [Qualitative Analytical Chemistry], 18th ed.; Thomson Paraninfo: Madrid, 2006; pp 175– 234.
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    Chen, D.; Ni, S.; Fang, J. J.; Xiao, T. Preparation of Cu2O nanoparticles in cupric chloride solutions with a simple mechanochemical approach. J. Alloys Compd. 2010, 504, S345– S348,  DOI: 10.1016/j.jallcom.2010.02.138
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    Effects of strontium on microstructure and mechanical properties of as-cast Mg-5 wt.%Sn alloy
    Liu, Hongmei; Chen, Yungui; Zhao, Haofeng; Wei, Shanghai; Gao, Wei
    Journal of Alloys and Compounds (2010), 504 (2), 345-350CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    The Sr addn. to the Mg-5 wt.%Sn alloy results in grain refinement and the formation of a rod-shaped and a bone-shaped MgSnSr intermetallic phase which is mainly located on the grain boundaries. The yield strength is improved, while the tensile strength and elongation first increased, and then decreased with a large addn. of Sr. Optimum mech. properties at ambient temp. are obtained for the alloy with 2.14 wt. %Sr. Tensile properties of the alloys at elevated temps. are also improved, and the decrease in strength at elevated temp. slowed down with increasing Sr addn., indicating that Sr can improve the thermal stability of Mg-Sn alloys.
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    Cudennec, Y.; Lecerf, A. The transformation of Cu(OH)2 into CuO, revisited. Solid State Sci. 2003, 5, 1471– 1474,  DOI: 10.1016/j.solidstatesciences.2003.09.009
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    The transformation of Cu(OH)2 into CuO, revisited
    Cudennec, Yannick; Lecerf, Andre
    Solid State Sciences (2003), 5 (11-12), 1471-1474CODEN: SSSCFJ; ISSN:1293-2558. (Elsevier SAS)
    Cu(OH)2 is metastable. It easily transforms into more stable CuO, either in the solid state by a thermal dehydration or at room temp., in aq. basic solns. In the solid state, the transformation was performed at a relatively low temp., 423 K. It is a topotactic or a pseudomorphic transformation owing to clear relations between axes of the two solids, in the three directions. The reacting process is described and the corresponding vectorial relations between crystal parameters are proposed. It is not the same case in aq. basic solns. Cu(OH)2 gives rise to CuO through the formation of a complex anion, Cu(OH)42-, by a reconstructive transformation involving a dissoln. reaction followed by a pptn.
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    (a) Shahmiri, M.; Ibrahim, N. A.; Zainuddin, N.; Asim, N.; Bakhtyar, B.; Zaharim, A.; Sopian, K. Effect of pH on the Synthesis of CuO Nanosheets by Quick Precipitation Method. WSEAS Trans. Environ. Dev. 2013, 2, 137– 146
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    (b) Shahmiri, M.; Ibrahim, N. A.; Shayesteh, F.; Asim, N.; Motallebi, N. Preparation of PVP-coated copper oxide nanosheets as antibacterial and antifungal agents. J. Mater. Res. 2013, 28, 3109– 3118,  DOI: 10.1557/jmr.2013.316
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    Preparation of PVP-coated copper oxide nanosheets as antibacterial and antifungal agents
    Shahmiri, Mahdi; Ibrahim, Nor Azowa; Shayesteh, Fatemeh; Asim, Nilofar; Motallebi, Nabi
    Journal of Materials Research (2013), 28 (22), 3109-3118CODEN: JMREEE; ISSN:2044-5326. (Cambridge University Press)
    Copper oxide (CuO) nanosheets synthesized in polyvinylpyrrolidone (PVP) were characterized with respect to antimicrobial activity by quick pptn. method. Different sizes and shapes of CuO nanosheets were obtained by simple variations of PVP concns. The x-ray diffraction results revealed the formation of pure-phase CuO with monoclinic structure. Transmission electron microscopy anal. showed that the av. ratio of length to width of these nanosheets increased with increasing PVP concns. Due to the quantum size effect, CuO nanosheets exhibit a blue shift in the UV-visible spectra. Field emission SEM results showed that as the concn. of PVP increased, well-defined morphologies were formed on the surface of the products. Energy dispersive anal. of x-ray clearly confirmed the presence of Cu and O with an at. ratio of 1:1. Fourier transform IR spectroscopy results showed that C=O in PVP coordinated with CuO and formed a protective layer. The mechanism of the reaction was also discussed. CuO nanosheets in suspension showed activity against a range of bacterial pathogens and fungi with min. bactericidal concns. (MBCs) ranging from 100 to 5000 μg/mL. The extent of the inhibition zones and the MBCs was found to be size-dependent.
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    Zhang, J.; Liu, J.; Peng, Q.; Wang, X.; Li, Y. Nearly Monodisperse Cu2O and CuO Nanospheres: Preparation and Applications for Sensitive Gas Sensors. Chem. Mater. 2006, 18, 867– 871,  DOI: 10.1021/cm052256f
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    Nearly Monodisperse Cu2O and CuO Nanospheres: Preparation and Applications for Sensitive Gas Sensors
    Zhang, Jiatao; Liu, Junfeng; Peng, Qing; Wang, Xun; Li, Yadong
    Chemistry of Materials (2006), 18 (4), 867-871CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    A low-temp. soln.-phase method for prepg. nearly monodisperse Cu2O and CuO nanospheres is presented. The rapid prodn. of supersatd. Cu2O nanocrystals and their regular spherical aggregation lead to the monodispersity of Cu2O nanospheres. By modulating the concn. of reactant H2O, the diam., crystn., and monodispersity of Cu2O nanospheres can be kinetically controlled. Because the thin films prepd. by as-obtained Cu2O nanospheres have large surface areas and plentiful spaces to interact with gases, the gas sensors based on as-prepd. Cu2O nanospheres have high sensitivity and good selectivity to some flammable gases. The surface modification with noble metals or n-type metal oxides based on obtained nanospheres will be helpful to enrich their sensor applications.
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    (a) La Mer, V. K. Nucleation in Phase Transitions. Ind. Eng. Chem. 1952, 44, 1270– 1277,  DOI: 10.1021/ie50510a027
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    Kinetics in phase transitions
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    Industrial and Engineering Chemistry (1952), 44 (), 1270-7CODEN: IECHAD; ISSN:0019-7866.
    A detailed review of conceptual and phenomenological aspects of nucleation processes including the historical development, Ostwald's clarifying views, the Volmer extension of Gibbs' fundamental equations for the work involved in forming a new phase, the statistical approach to the characterization and work of formation of embryos and nuclei, the rate of nucleus formation, heterogeneous nucleation and the application to the stability of polydisperse colloidal dispersions, the prepn. of monodisperse aerosols and hydrosols, and the time lag in the supersatn. of BaSO4.
    (b) La Mer, V. K.; Dinegar, R. H. Theory, Production and Mechanism of Formation of Monodispersed Hydrosols. J. Am. Chem. Soc. 1950, 72, 4847– 4854,  DOI: 10.1021/ja01167a001
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    Theory, production, and mechanism of formation of monodispersed hydrosols
    La Mer, Victor K.; Dinegar, Robert H.
    Journal of the American Chemical Society (1950), 72 (), 4847-54CODEN: JACSAT; ISSN:0002-7863.
    Monodispersed colloids exhibiting higher-order Tyndall spectra were prepd. by pptn. of S8 from EtOH and Me2CO solns. by the careful addn. of H2O. The relation between the concn. of S and the vol. fraction of H2O at the crit. point of S-EtOH-H2O solns. was investigated. Sols prepd. by this diln. method were investigated as to dispersion of wave length in their angular scattering of visible light and their transmission as a function of wave length. The size, no., and charge of the particles of such sols are in the same range as those prepd. by the acid decompn. of Na2S2O3. The rates of growth of sols prepd. by such a diln. method were investigated. The growth rates obtained were reproduced from theoretical considerations that allow the estn. of the value of the diffusion coeff. of S8 in EtOH-H2O and Me2CO-H2O mixts. The value of this diffusion coeff. lies in the range 7 to 8 × 10-6 cm.2/sec. for both media. The application of this method for estg. diffusion coeffs. is valid for any colloidal system that is characterized by a small particle-size distribution at all stages of its growth. A qual. explanation is offered for the necessary conditions under which monodispersed colloids can be prepd. for both the diln. and acid-decompn.-of-Na2S2O3 methods.
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    Thanh, N. T. K.; Maclean, N.; Mahiddine, S. Mechanisms of Nucleation and Growth of Nanoparticles in Solution. Chem. Rev. 2014, 114, 7610– 7630,  DOI: 10.1021/cr400544s
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    Mechanisms of Nucleation and Growth of Nanoparticles in Solution
    Thanh, Nguyen T. K.; MacLean, N.; Mahiddine, S.
    Chemical Reviews (Washington, DC, United States) (2014), 114 (15), 7610-7630CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. This work covers the area of crystal growth of nanoparticles in soln. The authors first discuss classical crystal growth and crystal nucleation and the formation of particle size distribution. They then continue the discussion of crystal growth with the coverage of the theories of the LaMer Mechanism, Ostwald Ripening, Digestive Ripening, Finke-Watzky two step mechanism, coalescence and orientated attachment, and intraparticle growth. They then discuss literature examples of nanoparticle formation of copper, silver, and gold noble metals, and metal oxides. The use of nanoparticle formation for the formation of quantum dots are also given.
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    Zhang, X.; Xie, Y.; Xu, F.; Liu, X.; Xu, D. Shape-controlled synthesis of submicro-sized cuprous oxide octahedra. Inorg. Chem. Commun. 2003, 6, 1390– 1392,  DOI: 10.1016/j.inoche.2003.09.002
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    Shape-controlled synthesis of submicro-sized cuprous oxide octahedra
    Zhang, Xu; Xie, Yi; Xu, Fen; Liu, Xiaohui; Xu, Di
    Inorganic Chemistry Communications (2003), 6 (11), 1390-1392CODEN: ICCOFP; ISSN:1387-7003. (Elsevier Science B.V.)
    Monodisperse submicro-sized cuprous oxide (Cu2O) octahedra are successfully prepd. in large quantities assisted by the capping reagent poly(vinyl pyrrolidone) (PVP-K30, MW = 58,000) and the formation mechanism of Cu2O octahedra is analyzed.
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    Guzman, A.; Arroyo, J.; Verde, L.; Rengifo, J. Synthesis and characterization of copper nanoparticles/polyvinyl chloride (Cu NPs/PVC) nanocomposites. Procedia Mater. Sci. 2015, 9, 298– 304,  DOI: 10.1016/j.mspro.2015.04.038
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    Synthesis and characterization of copper nanoparticles/polyvinyl chloride (Cu NPs/PVC) nanocomposites
    Guzman, A.; Arroyo, J.; Verde, L.; Rengifo, J.
    Procedia Materials Science (2015), 9 (), 298-304CODEN: PMSREM; ISSN:2211-8128. (Elsevier B.V.)
    In the present work, two-synthesis method for copper nanoparticles (Cu NPs) in polyvinyl chloride polymer (PVC) had been developed by adding previously synthesized NPs to the resin and by an in situ synthesis of the NPs. The resin was mixed with additives to enhance obtaining a pasty mixt. called plastisol. The obtained plastisol was liq. at room temp. and had viscoelastic and pseudoplastic properties. The plastisol showed changes in its mech. properties by heat action, like a remarkable increase of viscosity at high temps., passing from the initial liq. state to solid state at curing temp. (180-200°C). Cu NPs were synthesized previously by microwave assisted polyol method, using copper acetate (CuAc2) as precursor, ascorbic acid (AA) as reducing agent, polivinilpirrolidone (PVP) as stabilizer and ethylene glycol as solvent. In this synthesis ethylene glycol (EG), a diol widely used in polyol method; was used as a solvent. Microwaves provided thermal heating, an alternative to the conventional heating by convection. The microwave irradn. was successfully used to warm dielec. materials, considering the property of tangent loss (tan δ), the higher the value, the greater transformation of electromagnetic microwave energy into heat energy was achieved, this one occurs preferably in polyol, such as ethylene, which has high dielec. const. Different concns. of plasticizer and several temps. were evaluated for curing nanocomposites (Cu NPs/PVC). To obtain films of Cu NPs/PVC, a coating technique over a substrate (paper or fabric transfer) was used. Films were prepd. in order to produce a material with further bactericidal activity. The characterization was performed by x-ray diffraction and UV visible spectrophotometry.
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    Wu, S.; Liu, T.; Zeng, W.; He, J.; Yu, W.; Gou, Z. Rose-like Cu2O synthesized by assisted PVP K30 hydrothermal Method. J Mater Sci: Mater Electron. 2013, 24, 2404– 2409,  DOI: 10.1007/s10854-013-1109-2
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    Rose-like Cu2O synthesized by assisted PVP K30 hydrothermal method
    Wu, Shufang; Liu, Tianmo; Zeng, Wen; He, Jiejun; Yu, Weijie; Gou, Zhongping
    Journal of Materials Science: Materials in Electronics (2013), 24 (7), 2404-2409CODEN: JSMEEV; ISSN:0957-4522. (Springer)
    Rose-like Cu2O nanoflowers have been synthesized by polyvinylpyrrolidone K30 (PVP K30)-assisted hydrothermal method. Here, copper sulfate CuSO4 and sodium hydroxide NaOH were used as raw materials. The synthesized Cu2O powders were characterized by X-ray diffraction (XRD) and field emission SEM (FESEM). XRD pattern exhibited the nanocryst. nature with cubic structure for the synthesized nanostructures. FESEM images indicated that the rose-like Cu2O nanostructures are composed of many nearly rectangular shape nanosheets in size of about 1-2 μm in width and length and approx. 50-60 nm in thickness. Anal. results reveal that PVP K30 plays a vital role in formation of rose-like Cu2O nanoflower in this work. The probable formation mechanism of rose-like Cu2O nanoflower was discussed.
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    Zhang, X.; Yin, H.; Cheng, X.; Hu, H.; Yu, Q.; Wang, A. Effects of various polyoxyethylene sorbitan monooils (Tweens) and sodium dodecyl sulfate on reflux synthesis of copper nanoparticles. Mater. Res. Bull. 2006, 41, 2041– 2048,  DOI: 10.1016/j.materresbull.2006.04.008
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    Effects of various polyoxyethylene sorbitan monooils (Tweens) and sodium dodecyl sulfate on reflux synthesis of copper nanoparticles
    Zhang, Xifeng; Yin, Hengbo; Cheng, Xiaonong; Hu, Huifeng; Yu, Qi; Wang, Aili
    Materials Research Bulletin (2006), 41 (11), 2041-2048CODEN: MRBUAC; ISSN:0025-5408. (Elsevier B.V.)
    Size-controlled synthesis of phase pure Cu nanoparticles was carried out by using copper sulfate pentahydrate as a precursor, ascorbic acid as a reductant, Tweens and sodium dodecyl sulfate (SDS) as modifiers in an aq. soln. at 80°. The as-prepd. Cu nanoparticles were characterized by powder XRD, TEM, selected area electron diffraction (SAED), and FTIR. The stabilizing effects of SDS and Tweens on the Cu nanoparticles should be through the coordination between Cu nanoparticles and the resp. sulfate group and oxygen-contg. bond. The synergic effect of the composite SDS and Tweens on Cu nanoparticles was different from those arising from the individuals.
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    El-Nahhal, I. M.; Salem, J.; Anbar, R.; Kodeh, F. S.; Elmanama, A. Preparation and antimicrobial activity of ZnO-NPs coated cotton/starch and their functionalized ZnO-Ag/cotton and Zn(II) curcumin/cotton materials. Sci. Rep. 2020, 10, 5410  DOI: 10.1038/s41598-020-61306-6
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    Preparation and antimicrobial activity of ZnO-NPs coated cotton/starch and their functionalized ZnO-Ag/cotton and Zn(II) curcumin/cotton materials
    El-Nahhal, Issa M.; Salem, Jamil; Anbar, Rawan; Kodeh, Fawzi S.; Elmanama, Abdelraouf
    Scientific Reports (2020), 10 (1), 5410CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)
    ZnO-NPs coated cotton or starched cotton fibers were successfully prepd. via ultrasound irradn. Different concns. of sol. corn starch (1-3 starch wt.%) were used to stabilize ZnO-NPs onto the surface of cotton fabrics as entrapped species. The use of none-toxic biocompatible starch has improved the adhesion properties of the cotton fibers towards ZnO-NPs. This also enhanced the durability of ZnO-NPs onto the cotton fabrics and decreased their leaching from the surface of cotton fabrics. When 3 starch wt.% soln. was used, deposition of ZnO-NP increased by 53% after 10 washing cycles. The antibacterial activity against Staphylococcus aureus and Escherichia coli increased by 50 and 21.5%, resp. Functionalization of ZnO coated cotton with silver nanoparticles (Ag-NPs) and curcumin results in formation of ZnO-Ag/cotton and Zn(II) curcumin/cotton composites. The functionalized nanocomposites ZnO-Ag coated cotton material showed a synergistic antimicrobial behavior than that of individual ZnO/cotton material. The Zn(II) curcumin complex coated cotton showed higher antibacterial activities against both Staphylococcus aureus (Gram-pos.) and Escherichia coli (Gram-neg.) bacteria than that of the ZnO/cotton material.
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    El-Nahhal, I. M.; Elmanama, A. A.; El Ashgar, N. A.; Amara, N.; Selmane, M.; Chehimi, M. C. Stabilization of nano-structured ZnO particles onto the surface of cotton fibers using different surfactants and their antimicrobial activity. Ultrason. Sonochem. 2017, 38, 478– 487,  DOI: 10.1016/j.ultsonch.2017.03.050
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    Stabilization of nano-structured ZnO particles onto the surface of cotton fibers using different surfactants and their antimicrobial activity
    El-Nahhal, Issa M.; Manamah, Abed El Raouf; Al Ashgar, Nizam M.; Amara, Nadia; Selmane, Mohamed; Chehimi, Mohamed M.
    Ultrasonics Sonochemistry (2017), 38 (), 478-487CODEN: ULSOER; ISSN:1350-4177. (Elsevier B.V.)
    ZnO NPs were prepd. and deposited onto cotton fibers via ultrasound irradn. successfully. Different surfactants (SDS, HY, CTAB, TX-100) have been used to stabilize, homogenize the coated ZnO NPs and control their shape and size as encapsulated species. The use of surfactants has improved the durability of ZnO NPs and decreased its leaching in particular SDS. The small mean crystallite size for ZnO particles due to the use of surfactants is the main reason for decreasing the leached of ZnO particles from cotton substrate. SEM and XRD anal. revealed information about the shape and size of the coated ZnO nanoparticles. The use of SDS and HY surfactants in the synthesis of ZnO NPs coated fabrics showed the highest antibacterial and antifungal activities against different pathogenic bacterial and fungal species with high redn. reached over 90%.
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    Román, L. E.; Gomez, E. D.; Solís, J. L.; Gómez, M. M. Antibacterial Cotton Fabric Functionalized with Copper Oxide Nanoparticles. Molecules 2020, 25, 5802  DOI: 10.3390/molecules25245802
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    Antibacterial cotton fabric functionalized with copper oxide nanoparticles
    Roman, Luz E.; Gomez, Enrique D.; Solis, Jose L.; Gomez, Monica M.
    Molecules (2020), 25 (24), 5802CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
    Textiles functionalized with cupric oxide (CuO) nanoparticles have become a promising option to prevent the spread of diseases due to their antimicrobial properties, which strongly depend on the structure and morphol. of the nanoparticles and the method used for the functionalization process. This article presents a review of work focused on textiles functionalized with CuO nanoparticles, which were classified into two groups, namely, in situ and ex situ. Moreover, the analyzed bacterial strains, the resistance of the antimicrobial properties of textiles to washing processes, and their cytotoxicity were identified. Finally, the possible antimicrobial mechanisms that could develop in Gram-pos. and Gram-neg. bacteria were described.
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    Naika, H. R.; Lingaraju, K.; Manjunath, K.; Kumar, D.; Nagaraju, G.; Suresh, D.; Nagabhushana, H. Green synthesis of CuO nanoparticles using Gloriosa superba L. extract and their antibacterial activity. J. Taibah Univ. Sci. 2015, 9, 7– 12,  DOI: 10.1016/j.jtusci.2014.04.006
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    (a) Azam, A.; Ahmed, A. S.; Oves, M.; Khan, M. S.; Habib, S. S.; Memic, A. Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study. Int. J. Nanomed. 2012, 7, 6003– 6009,  DOI: 10.2147/IJN.S35347
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    Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study
    Azam, Ameer; Ahmed, Arham S.; Oves, Mohammad; Khan, Mohammad S.; Habib, Sami S.; Memic, Adnan
    International Journal of Nanomedicine (2012), 7 (), 6003-6009CODEN: IJNNHQ; ISSN:1178-2013. (Dove Medical Press Ltd.)
    Background: Nanomaterials have unique properties compared to their bulk counterparts. For this reason, nanotechnol. has attracted a great deal of attention from the scientific community. Metal oxide nanomaterials like ZnO and CuO have been used industrially for several purposes, including cosmetics, paints, plastics and textiles. A common feature that these nanoparticles exhibit is their antimicrobial behavior against pathogenic bacteria. In this report, we demonstrate the antimicrobial activity of ZnO, CuO and Fe2O3 nanoparticles against Gram-pos. and Gram-neg. bacteria. Methods and Results: Nanosized particles of three metal oxides (ZnO, CuO and Fe2O3) were synthesized by a sol-gel combustion route and characterized by X-ray diffraction, Fourier-transform IR spectroscopy and transmission electron microscopy techniques. X-ray diffraction results confirmed the single-phase formation of all three nanomaterials. The particle sizes were obsd. to be 18, 22 and 28 nm for ZnO, CuO and Fe2O3, resp. We used these nanomaterials to evaluate their antibacterial activity against both Gram-neg. (Escherichia coli and Pseudomonas aeruginosa) and Gram-pos. (Staphylococcus aureus and Bacillus subtilis) bacteria. Conclusion: Among the three metal oxide nanomaterials, ZnO showed greatest antimicrobial activity against both Gram-pos. and Gram-neg. bacteria used in this study. It was obsd. that ZnO nanoparticles have excellent bactericidal potential, while Fe2O3 nanoparticles exhibited the least bactericidal activity. The order of antibacterial activity was demonstrated to be the following: ZnO > CuO > Fe2O3.
    (b) Azam, A.; Ahmed, A. S.; Oves, M.; Khan, M. S.; Habib, S. S.; Memic, A. Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study. Int. J. Nanomed. 2012, 7, 6003– 6009,  DOI: 10.2147/IJN.S35347
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    Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study
    Azam, Ameer; Ahmed, Arham S.; Oves, Mohammad; Khan, Mohammad S.; Habib, Sami S.; Memic, Adnan
    International Journal of Nanomedicine (2012), 7 (), 6003-6009CODEN: IJNNHQ; ISSN:1178-2013. (Dove Medical Press Ltd.)
    Background: Nanomaterials have unique properties compared to their bulk counterparts. For this reason, nanotechnol. has attracted a great deal of attention from the scientific community. Metal oxide nanomaterials like ZnO and CuO have been used industrially for several purposes, including cosmetics, paints, plastics and textiles. A common feature that these nanoparticles exhibit is their antimicrobial behavior against pathogenic bacteria. In this report, we demonstrate the antimicrobial activity of ZnO, CuO and Fe2O3 nanoparticles against Gram-pos. and Gram-neg. bacteria. Methods and Results: Nanosized particles of three metal oxides (ZnO, CuO and Fe2O3) were synthesized by a sol-gel combustion route and characterized by X-ray diffraction, Fourier-transform IR spectroscopy and transmission electron microscopy techniques. X-ray diffraction results confirmed the single-phase formation of all three nanomaterials. The particle sizes were obsd. to be 18, 22 and 28 nm for ZnO, CuO and Fe2O3, resp. We used these nanomaterials to evaluate their antibacterial activity against both Gram-neg. (Escherichia coli and Pseudomonas aeruginosa) and Gram-pos. (Staphylococcus aureus and Bacillus subtilis) bacteria. Conclusion: Among the three metal oxide nanomaterials, ZnO showed greatest antimicrobial activity against both Gram-pos. and Gram-neg. bacteria used in this study. It was obsd. that ZnO nanoparticles have excellent bactericidal potential, while Fe2O3 nanoparticles exhibited the least bactericidal activity. The order of antibacterial activity was demonstrated to be the following: ZnO > CuO > Fe2O3.
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    Abboud, Y.; Saffaj, T.; Chagraoui, A.; El Bouari, A.; Brouzi, K.; Tanane, O.; Ihssane, B. Biosynthesis, characterization and antimicrobial activity of copper oxide nanoparticles (CONPs) produced using brown alga extract (Bifurcaria bifurcata). Appl. Nanosci. 2014, 4, 571– 576,  DOI: 10.1007/s13204-013-0233-x
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    Biosynthesis, characterization and antimicrobial activity of copper oxide nanoparticles (CONPs) produced using brown alga extract (Bifurcaria bifurcata)
    Abboud, Y.; Saffaj, T.; Chagraoui, A.; El Bouari, A.; Brouzi, K.; Tanane, O.; Ihssane, B.
    Applied Nanoscience (2014), 4 (5), 571-576CODEN: ANPACY; ISSN:2190-5517. (Springer GmbH)
    Recently, biosynthesis of nanoparticles has attracted scientists' attention because of the necessity to develop new clean, cost-effective and efficient synthesis techniques. In particular, metal oxide nanoparticles are receiving increasing attention in a large variety of applications. However, up to now, the reports on the biopreparation and characterization of nanocryst. copper oxide are relatively few compared to some other metal oxides. In this paper, we report for the first time the use of brown alga (Bifurcaria bifurcata) in the biosynthesis of copper oxide nanoparticles of dimensions 5-45 nm. The synthesized nanomaterial is characterized by UV-visible absorption spectroscopy and Fourier transform IR spectrum anal. X-ray diffraction confirms the formation and the cryst. nature of copper oxide nanomaterial. Further, these nanoparticles were found to exhibit high antibacterial activity against two different strains of bacteria Enterobacter aerogenes (Gram neg.) and Staphylococcus aureus (Gram pos.).
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    Speranza, G.; Gottardi, G.; Pederzolli, C.; Lunelli, L.; Canteri, R.; Pasquardini, L. Role of chemical interactions in bacterial adhesion to polymer surfaces. Biomaterials 2004, 25, 2029– 2037,  DOI: 10.1016/j.biomaterials.2003.08.061
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    Role of chemical interactions in bacterial adhesion to polymer surfaces
    Speranza, G.; Gottardi, G.; Pederzolli, C.; Lunelli, L.; Canteri, R.; Pasquardini, L.; Carli, E.; Lui, A.; Maniglio, D.; Brugnara, M.; Anderle, M.
    Biomaterials (2004), 25 (11), 2029-2037CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
    Development of biomaterial-related infections is attracting an increasing interest due to the significant percentage of implant failure in the hospital care. Recent literature puts in evidence the dependence of the infection risk on the different biomaterials used, because of the different interactions between material surface and micro-organisms. Despite this, the mechanisms underlying the adhesion of bacteria to the biomaterial surface are still unclear. Aim of this work was to study the initial events of the processes responsible for the bacterial adhesion on polymers in order to prevent the development of bacterial infections and the consequent failure and replacement of biomedical devices. Electrostatic and Lifshitz-van der Waals forces are usually considered responsible for the interactions at the biomaterial interface. A new term that involves Lewis acid-base interactions was here introduced to better describe the bacterial adhesion to the polymer surface. Two requirements are needed to test this hypothesis: the development of an ideal polymeric surface in terms of chem. and morphol. properties and the choice of a specific bacterial strain to be utilized as "probe". Expts. were worked out using an Escherichia coli (Gram-) strain that represent one of the principal isolates from infected biomaterial implants and its adhesion was investigated on polymers having different acid/basic character. The findings indicated that the bacterial adhesion is influenced by the chem. properties of the polymeric surface. These results may be interpreted taking into account a mechanism in which the acid/base (Lewis) interaction plays an important role.
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    Guzman, M.; Dille, J.; Godet, S. Synthesis and antibacterial activity of silver nanoparticles against gram-positive and gram-negative bacteria. Nanomedicine 2012, 8, 37– 45,  DOI: 10.1016/j.nano.2011.05.007
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    Synthesis and antibacterial activity of silver nanoparticles against gram-positive and gram-negative bacteria
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    Synthesis of nanosized particles with antibacterial properties is of great interest in the development of new pharmaceutical products. Silver nanoparticles (Ag NPs) are known to have inhibitory and bactericidal effects. In this article we present the synthesis of Ag NPs prepd. by chem. redn. from aq. solns. of silver nitrate, contg. a mixt. of hydrazine hydrate and sodium citrate as reductants and sodium dodecyl sulfate as a stabilizer. The results of the characterization of the Ag NPs show agglomerates of grains with a narrow size distribution (from 40 to 60 nm), whereas the radii of the individual particles are between 10 and 20 nm. Finally, the antibacterial activity was measured by the Kirby-Bauer method. The results showed reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The std. diln. micromethod, detg. the min. inhibitory concn. leading to inhibition of bacterial growth, is still under way. Preliminary results have been obtained. From the Clin. Editor: In this paper the synthesis of Ag NPs via chem. redn. from aq. solns. is discussed. Reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus was demonstrated.
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    Copper oxide (CuO) nanoparticles were characterized and investigated with respect to potential antimicrobial applications. It was found that nanoscaled CuO, generated by thermal plasma technol., contains traces of pure Cu and Cu2O nanoparticles. Transmission electron microscopy (TEM) demonstrated particle sizes in the range 20-95 nm. TEM energy dispersive spectroscopy gave the ratio of copper to oxygen elements as 54.18% to 45.26%. The mean surface area was detd. as 15.69 m2/g by Brunau-Emmet-Teller (BET) anal. CuO nanoparticles in suspension showed activity against a range of bacterial pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli, with min. bactericidal concns. (MBCs) ranging from 100 μg/mL to 5000 μg/mL. The ability of CuO nanoparticles to reduce bacterial populations to zero was enhanced in the presence of sub-MBC concns. of silver nanoparticles. Studies of CuO nanoparticles incorporated into polymers suggest release of ions may be required for optimum killing.
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    The essential yet toxic nature of copper demands tight regulation of the copper homeostatic machinery to ensure that sufficient copper is present in the cell to drive essential biochem. processes yet prevent the accumulation to toxic levels. In Saccharomyces cerevisiae, the nutritional copper sensor Mac1p regulates the copper-dependent expression of the high affinity Cu(I) uptake genes CTR1, CTR3, and FRE1, while the toxic copper sensor Ace1p regulates the transcriptional activation of the detoxification genes CUP1, CRS5, and SOD1 in response to copper. In this study, the authors characterized the tandem regulation of the copper uptake and detoxification pathways in response to the chronic presence of elevated concns. of copper ions in the growth medium. Upon addn. of CuSO4, mRNA levels of CTR3 were rapidly reduced to eightfold the original basal level whereas the Ace1p-mediated transcriptional activation of CUP1 was rapid and potent but transient. CUP1 expression driven by an Ace1p DNA binding domain-herpes simplex virus VP16 transactivation domain fusion was also transient, demonstrating that this mode of regulation occurs via modulation of the Ace1p copper-activated DNA binding domain. In vivo di-Me sulfate footprinting anal. of the CUP1 promoter demonstrated transient occupation of the metal response elements by Ace1p which paralleled CUP1 mRNA expression. Anal. of a Mac1p mutant, refractile for copper-dependent repression of the Cu(I) transport genes, showed an aberrant pattern of CUP1 expression and copper sensitivity. These studies (i) demonstrate that the nutritional and toxic copper metalloregulatory transcription factors Mac1p and Ace1p must sense and respond to copper ions in a dynamic fashion to appropriately regulate copper ion homeostasis and (ii) establish the requirement for a wild-type Mac1p for survival in the presence of toxic copper levels.
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    Kim, J. H.; Cho, H.; Ryu, S. E.; Choi, M. U. Effects of metals ions on the activity of protein tyrosine phosphate VHR: Highly potent and reversible oxidative inactivation by Cu2O ion. Arch. Biochem. Biophys. 2000, 382, 72– 80,  DOI: 10.1006/abbi.2000.1996
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    Effects of Metal Ions on the Activity of Protein Tyrosine Phosphatase VHR: Highly Potent and Reversible Oxidative Inactivation by Cu2+ Ion
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    Archives of Biochemistry and Biophysics (2000), 382 (1), 72-80CODEN: ABBIA4; ISSN:0003-9861. (Academic Press)
    The posttranslational regulation of protein tyrosine phosphatases (PTPs) has been suggested to have a crucial role in maintaining the phosphotyrosine level in cells. Here we examd. the regulatory effects of metal ions on human dual-specificity vaccinia H1-related protein tyrosine phosphatase (VHR) in vitro. Among various metal ions examd., Fe3+, Cu2+, Zn2+, and Cd2+ exerted their inactivation effects on VHR, and Cu2+ is the most potent inactivator. The VHR activity inactivated by the metal ions except Cu2+ was significantly restored by EDTA. The efficacy of Cu2+ for the VHR inactivation was about 200-fold more potent than that of H2O2. Cu2+ also inactivated other PTPs including PTP1B and SHP-1. The Cu2+-mediated inactivation at the submicromolar range was eradicated by dithiothreitol treatment. The loss of VHR activity correlated with the decreased [14C]iodoacetate labeling of active-site cysteine, suggesting that Cu2+ brought about the oxidn. of the active-site cysteine. In contrast, Zn2+ that exerted an inactivation effect at millimolar concns. appeared not directly linked to the active-site cysteine, as indicated by the fact that [14C]iodoacetate labeling was unaffected and that the effect of Zn2+ on the Y78F mutant was increased. The redn. potential of VHR was estd. to be -331 mV by utilizing the reversibility of the redox state of VHR. Thus, we conclude that the highly potent Cu2+ inactivation of VHR is a consequence of the oxidn. of the active-site cysteine and the mode of Zn2+ inactivation is distinct from that of Cu2+. (c) 2000 Academic Press.
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    Guzman, M.; Arcos, M.; Dille, J.; Godet, S.; Rousse, C. Effect of the Concentration of NaBH4 and N2H4 as Reductant Agent on the Synthesis of Copper Oxide Nanoparticles and its Potential Antimicrobial Applications. Nano Biomed. Eng. 2018, 10, 392– 405,  DOI: 10.5101/nbe.v10i4.p392-405
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    Effect of the concentration of NaBH4 and N2H4 as reductant agent on the synthesis of copper oxide nanoparticles and its potential antimicrobial applications
    Guzman, Maribel; Arcos, Mariella; Dille, Jean; Godet, Stephane; Rousse, Celine
    Nano Biomedicine and Engineering (2018), 10 (4), 392-405CODEN: NBEAA2; ISSN:2150-5578. (Nano Biomedicine and Engineering)
    The antibacterial activity of various nanoparticles is gaining increasing interest due to its potential medical applications. In this work, we presented the synthesis of copper oxide nanoparticles prepd. by chem. redn. from aq. solns. of copper sulfate (CuSO4) with sodium borohydride (NaBH4) and hydrazine hydrate (N2H4) as reductant and polyvinylpyrrolidone (PVP) as stabilizer. The X-ray diffraction spectra showed the formation of tenorite (CuO) and cuprite (Cu2O) nanoparticles when different ratios of CuSO4/NaBH4 and CuSO4/N2H4 were used. Photographs obtained by transmission electron microscopy (TEM) showed agglomerates of grains with a narrow size distribution (from 20 to 70 nm), whereas the radii of the individual particles were between 2 and 20 nm. Smaller nanoparticles and narrower particle size distributions were obtained when NaBH4 was used. The results of antibacterial activity using the Kirby-Bauer method showed that nanoparticles obtained with NaBH4 presented a reasonable bactericidal activity. Pseudomonas aureginosa and Staphylococcus aureus were more susceptible to the particle size than Escherichia coli. In addn., with small amts. of Cu2O in samples of CuO nanoparticles, the antibacterial susceptibility against Pseudomonas aureginosa was improved. Finally, nanoparticles of CuO incorporated into cotton by applying ultrasound waves remained impregnated after five washes.
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    Copper/Copper oxide (Cu/Cu2O) nanoparticles were synthesized by modified chem. redn. method in an aq. medium using hydrazine as reducing agent and copper sulfate pentahydrate as precursor. The Cu/Cu2O nanoparticles were characterized by X-ray Diffraction (XRD), Energy Disper-sive X-ray Fluorescence (EDXRF), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The anal. revealed the pattern of face-centered cubic (fcc) crystal structure of copper Cu metal and cubic cuprites structure for Cu2O. The SEM result showed monodispersed and ag-glomerated particles with two micron sizes of about 180 nm and 800 nm, resp. The TEM result showed few single crystal particles of face-centered cubic structures with av. particle size about 11-14 nm. The catalytic activity of Cu/Cu2O nanoparticles for the decompn. of hydrogen peroxide was investigated and compared with manganese oxide MnO2. The results showed that the second-order equation provides the best correlation for the catalytic decompn. of H2O2 on Cu/Cu2O. The catalytic activity of hydrogen peroxide by Cu/Cu2O is less than the catalytic activity of MnO2 due to the presence of copper metal Cu with cuprous oxide Cu2O. 2015 BCREC UNDIP. All rights reserved.
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    A method for the prodn. of antibacterial ZnO nanoparticles has been developed. The technique combines passing an elec. current with simultaneous application of ultrasonic waves. By using high-power ultrasound a cavitation zone is created between two zinc electrodes. This leads to the possibility to create a spatial elec. discharge in water. Creation of such discharge leads to the depletion of the electrodes and the formation of ZnO nanoparticles, which demonstrate antibacterial properties. At the end of this reaction the suspension of ZnO nanoparticles is transported to a specially developed ultrasonic reactor, in which the nanoparticles are deposited on the textile. The nanoparticles are embedded into the fibers by the cavitation jets, which are formed by asym. collapsing bubbles in the presence of a solid surface and are directed towards the surface of textile at very high velocities. Fabrics coated with ZnO nanoparticles by using the developed method showed good antibacterial activity against E. coli.
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  • Abstract

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    Figure 1

    Figure 1. EDS spectrum of (a) samples MBS01 and (b) MBP01 and (c) X-ray diffraction (XRD) spectra of copper oxide nanoparticles obtained at different ratios of Cu/SDS = 0.90 (MBS01) and Cu/PVP = 0.81 (MBP01).

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    Figure 2

    Figure 2. TEM micrographs of CuO nanoparticles prepared at different ratios of (a) Cu/SDS = 0.9 and (b) Cu/PVP = 0.81 and details of nanoparticles prepared with (c, d) SDS and (e, f) PVP.

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    Figure 3

    Figure 3. EDS spectrum of samples (a) MBP01A and (b) MBP01B and (c) XRD spectra of copper oxide nanoparticles prepared at different Cu/PVP ratios (1.62; 0.81; 0.54).

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    Figure 4

    Figure 4. TEM micrographs of copper oxide nanoparticles prepared at different Cu/PVP ratios: (a) 1.62, (b) 0.81, and (c) 0.54. (d–i) Details of nanoparticles prepared with PVP at different concentrations.

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    Figure 5

    Figure 5. EDS spectrum of (a) sample MDS01 and XRD spectra of copper oxide nanoparticles prepared at different times of dispersant addition: (b) Cu/SDS = 0.9 (0 min) and 0.9 (30 min), (c) Cu/PVP = 0.81 (0 min) and 0.81 (30 min), and (d) Cu/PVP = 1.62 (0 min) and 1.62 (30 min).

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    Figure 6

    Figure 6. TEM micrographs of copper oxide nanoparticles prepared at different ratios of (a) Cu/SDS = 0.9 (30 min), (b) Cu/PVP = 1.62 (30 min), and (c) Cu/PVP = 0.81 (30 min) and details of nanoparticles prepared with (d, e) SDS and (f, i) PVP at different concentrations.

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    Figure 7

    Figure 7. (a) Cotton fabric before and after nanoparticle deposition and scanning electron microscopy (SEM) images of (b) the original cotton fiber, (c) MDS01-CF, (d) MDS01-CF after washing, (e) MDP01-CF, and (f) MDP01-CF after washing.

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    Figure 8

    Figure 8. Results of the diffusion test of copper oxide nanoparticles against Gram-positive and Gram-negative strains.

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      Bai, Yakui; Yang, Tengfei; Gu, Qing; Cheng, Guoan; Zheng, Ruiting
      Powder Technology (2012), 227 (), 35-42CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
      Cuprous oxide (Cu2O) nanoparticles with various particle shapes were synthesized via colloidal chem. approach. Using ascorbic acid as a reducing agent and polyvinylpyrrolidone (PVP) as a surfactant, cuprous oxide monocryst. nanoparticles with various sizes have been successfully synthesized by reaction of bivalent copper in aq. soln. The samples were characterized by XRD, SEM and UVs spectroscopy. The results indicate the shape of as-prepd. cuprous oxide nanoparticles has close relationship with thermodn. conditions, kinetic conditions and stirring rate. Self-assembly mechanism of cubic cuprous oxide monocryst. nanoparticles has also been investigated.
    2. 2
      (a) Ramyadevi, J.; Jeyasubramanian, K.; Marikani, A.; Rajakumar, G.; Rahuman, A. A. Synthesis and antimicrobial activity of copper nanoparticles. Mater. Lett. 2012, 71, 114– 116,  DOI: 10.1016/j.matlet.2011.12.055
      2a
      Synthesis and antimicrobial activity of copper nanoparticles
      Ramyadevi, Jeyaraman; Jeyasubramanian, Kadarkaraithangam; Marikani, Arumugam; Rajakumar, Govindasamy; Abdul Rahuman, Abdul
      Materials Letters (2012), 71 (), 114-116CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      Cu nanoparticles were prepd. using modified polyol method by the redn. of copper acetate hydrate in the presence of Tween 80 by refluxing between 190 and 200°. The x-ray diffraction pattern was used to analyze the formations of phase and crystal structure. The antimicrobial activity was carried out against Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, fungus like Aspergillus flavus, Aspergillus niger, and Candida albicans. The Cu nanoparticles showed more inhibitory activity in bacteria than the fungus and it also showed more zone of inhibition in E.coli (26 mm) than C. albicans (23 mm).
      (b) Pal, S.; Tak, Y. K.; Song, J. M. Does the Antibacterial Activity of Silver Nanoparticles Depend on the Shape of the Nanoparticle? A Study of the Gram-Negative Bacterium Escherichia coli. Appl. Environ. Microbiol 2007, 73, 1712– 1720,  DOI: 10.1128/AEM.02218-06
      2b
      Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the Gram-negative bacterium Escherichia coli
      Pal, Sukdeb; Tak, Yu Kyung; Song, Joon Myong
      Applied and Environmental Microbiology (2007), 73 (6), 1712-1720CODEN: AEMIDF; ISSN:0099-2240. (American Society for Microbiology)
      The authors investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-neg. bacterium Escherichia coli, both in liq. systems and on agar plates. Energy-filtering TEM images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag+ (in the form of AgNO3). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To the authors' knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and the authors' results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-neg. organism E. coli.
    3. 3
      Jillani, S.; Jelani, M.; Hassan, N. U.; Ahmad, S.; Hafeez, M. Synthesis, characterization and biological studies of copper oxide nanostructures. Mater. Res. Express 2018, 5, 045006  DOI: 10.1088/2053-1591/aab864
      3
      Synthesis, characterization and biological studies of copper oxide nanostructures
      Jillani, Saquf; Jelani, Mohsan; Ul Hassan, Najam; Ahmad, Shahbaz; Hafeez, Muhammad
      Materials Research Express (2018), 5 (4), 045006/1-045006/8CODEN: MREAC3; ISSN:2053-1591. (IOP Publishing Ltd.)
      The development of synthetic methods has been broadly accepted as an area of fundamental importance to the understanding and application of nanoscale materials. It allows the individual to modulate basic parameters such as morphol., particle size, size distributions, and compn. Several methods have been developed to synthesize CuO nanostructures with diverse morphologies, sizes, and dimensions using different chem. and phys. based approaches. In this work, CuO nanostructures have been synthesized by aq. pptn. method and simple chem. deposition method. The characterization of these products has been carried out by the x-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform IR (FTIR) and UV-vis spectroscopy. Biol. activity such as antibacterial nature of synthesized CuO is also explored. XRD peaks anal. revealed the monoclinic cryst. phase of copper oxide nanostructures. While the rod-like and particle-like morphologies have been obsd. in SEM results. FTIR spectra have confirmed the formation of CuO nanoparticles by exhibiting its characteristic peaks corresponding to 494 cm-1 and 604 cm-1. The energy band gap of the as-prepd. CuO nanostructures detd. from UV-vis spectra is found to be 2.18 eV and 2.0 eV for pptn. and chem. deposited samples resp. The antibacterial activity results described that the synthesized CuO nanoparticles showed better activity against Staphylococcus aureus.
    4. 4
      (a) El-Nahhal, I. M.; Elmanama, A. A.; Amara, N. A. Synthesis of Nanometal Oxide–Coated Cotton Composites. In Cotton Research; Abdurakhmonov, Y. I., Ed.; IntechOpen: London, 2016; pp 279– 297.
      There is no corresponding record for this reference.
      (b) Rivero, P. J.; Urrutia, A.; Goicoechea, J.; Arregui, F. J. Nanomaterials for Functional Textiles and Fibers. Nanoscale Res Lett. 2015, 10, 501  DOI: 10.1186/s11671-015-1195-6
      4b
      Nanomaterials for Functional Textiles and Fibers
      Rivero Pedro J; Urrutia Aitor; Goicoechea Javier; Arregui Francisco J
      Nanoscale research letters (2015), 10 (1), 501 ISSN:1931-7573.
      Nanoparticles are very interesting because of their surface properties, different from bulk materials. Such properties make possible to endow ordinary products with new functionalities. Their relatively low cost with respect to other nano-additives make them a promising choice for industrial mass-production systems. Nanoparticles of different kind of materials such as silver, titania, and zinc oxide have been used in the functionalization of fibers and fabrics achieving significantly improved products with new macroscopic properties. This article reviews the most relevant approaches for incorporating such nanoparticles into synthetic fibers used traditionally in the textile industry allowing to give a solution to traditional problems for textiles such as the microorganism growth onto fibers, flammability, robustness against ultraviolet radiation, and many others. In addition, the incorporation of such nanoparticles into special ultrathin fibers is also analyzed. In this field, electrospinning is a very promising technique that allows the fabrication of ultrathin fiber mats with an extraordinary control of their structure and properties, being an ideal alternative for applications such as wound healing or even functional membranes.
      (c) Sedighi, A.; Montazer, M.; Samadi, N. Synthesis of nano Cu2O on cotton: Morphological, physical, biological and optical sensing characterizations. Carbohydr. Polym. 2014, 110, 489– 498,  DOI: 10.1016/j.carbpol.2014.04.030
      4c
      Synthesis of nano Cu2O on cotton: Morphological, physical, biological and optical sensing characterizations
      Sedighi, Ali; Montazer, Majid; Samadi, Nasrin
      Carbohydrate Polymers (2014), 110 (), 489-498CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
      In this paper, Cu2O nanoparticles were in situ synthesized on cotton fabric through a new simple and cost-effective chem. redn. method using copper sulfate, sodium hydroxide and ammonia. Cotton fabric participates as a reducing agent in redn. of copper sulfate and facilitates synthesis of cuprous oxide in nano-scale as a stabilizer. The produced cotton/nano Cu2O composite were characterized by X-ray diffraction, SEM and Energy-dispersive X-ray spectroscopy. Interaction of Cu2O with cotton fabric in addn. to alteration of cotton functional groups were studied by Fourier transforms IR spectroscopy. The intermediate soln., copper-amine complex, was analyzed by UV-visible spectroscopy. The mech. properties of the cotton/nano Cu2O composite were studied using Instron indicated a higher tensile strain. The antibacterial activity of the fabric samples showed considerable behavior against S. aureus and E. coli. Further, the treated fabric became highly hydrophobic and sensed ammonia and hydrogen peroxide chromatically.
      (d) El-Nahhal, I. M.; Zourab, S. M.; Kodeh, F. S.; Selmane, M.; Genois, I.; Babonneau, F. Nanostructured copper oxide-cotton fibers: synthesis, characterization, and applications. Int. Nano Lett. 2012, 2, 14  DOI: 10.1186/2228-5326-2-14
      There is no corresponding record for this reference.
    5. 5
      Khodashenas, B.; Ghorbani, H. R. Synthesis of copper nanoparticles: An overview of the various methods. Korean J. Chem. Eng. 2014, 31, 1105– 1109,  DOI: 10.1007/s11814-014-0127-y
      5
      Synthesis of copper nanoparticles : An overview of the various methods
      Khodashenas, Bahareh; Ghorbani, Hamid Reza
      Korean Journal of Chemical Engineering (2014), 31 (7), 1105-1109CODEN: KJCHE6; ISSN:0256-1115. (Springer)
      The synthesis of metal nanoparticles has received much attention due to their wide range of applications. Copper nanoparticles have attracted much attention due to their unique optical and elec. properties. Copper is relatively cheap in comparison to precious metals like gold and silver and also has high antibacterial properties. This review gives a brief overview of the available research works considering the synthesis of copper nanoparticles by chem., phys., and biol. methods.
    6. 6
      Das, D.; Nath, B. C.; Phukon, P.; Dolui, S. K. Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles. Colloids Surf., B 2013, 101, 430– 433,  DOI: 10.1016/j.colsurfb.2012.07.002
      6
      Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles
      Das, Dhaneswar; Nath, Bikash Chandra; Phukon, Pinkee; Dolui, Swapan Kumar
      Colloids and Surfaces, B: Biointerfaces (2013), 101 (), 430-433CODEN: CSBBEQ; ISSN:0927-7765. (Elsevier B.V.)
      CuO nanoparticles were synthesized by thermal decompn. methods and characterized by UV-visible spectroscopy, XRD and TEM anal. The resultant particles are nearly spherical and particle size is in the range of 15-30 nm. The antioxidant behavior of synthesized CuO nanoparticles was evaluated by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The free radical scavenging activity of CuO nanoparticles was monitored by UV-visible spectrophotometry. The antibacterial activity of CuO nanoparticles was tested against different bacterial strains. CuO nanoparticles showed efficient antioxidant activity and bactericidal effect against Escherichia coli and Pseudomonas aeruginosa.
    7. 7
      Salavati-Niasari, M.; Davar, F. Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor. Mater. Lett. 2009, 63, 441– 443,  DOI: 10.1016/j.matlet.2008.11.023
      7
      Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor
      Salavati-Niasari, Masoud; Davar, Fatemeh
      Materials Letters (2009), 63 (3-4), 441-443CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      The present investigation reports, the prepn. of nanoparticles Cu and Cu2O using thermal decompn. and its physicochem. characterization. The nanoparticles copper powder were prepd. using [bis(salicylidiminato)copper(II)], [Cu(sal)2], as precursor. Cu nanoparticles are initially formed and subsequently oxidized to form Cu2O. TEM demonstrated nanoparticles Cu2O with an av. diam. of ≈10 nm. As-prepd. Cu nanoparticles were characterized by x-ray diffraction measurements (XRD), SEM, energy dispersive anal. of x-rays (EDAX), and FTIR. XRD anal. revealed broad pattern for fcc. crystal structure of copper metal and cubic cuprite structure for Cu2O. Optical absorption measured by UV-visible spectroscopy was used to monitor oxidn. course of Cu → Cu2O and to det. the band-gap energy about 2.4 eV for Cu2O nanoshells.
    8. 8
      Zhou, L. J.; Zou, Y. C.; Zhao, J.; Wang, P. P.; Feng, L. L.; Sun, L. W. Facile synthesis of highly stable and porous Cu2O/CuO cubes with enhanced gas sensing properties. Sens. Actuators, B 2013, 188, 533– 539,  DOI: 10.1016/j.snb.2013.07.059
      8
      Facile synthesis of highly stable and porous Cu2O/CuO cubes with enhanced gas sensing properties
      Zhou, Li-Jing; Zou, Yong-Cun; Zhao, Jun; Wang, Pei-Pei; Feng, Liang-Liang; Sun, Li-Wei; Wang, De-Jun; Li, Guo-Dong
      Sensors and Actuators, B: Chemical (2013), 188 (), 533-539CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
      Highly stable and porous Cu2O/CuO cubes were prepd. by the calcination of the precursor at different temps. (350, 450, and 550°). The precursor which consists of cupric oxalate and cubic Cu2O was obtained by a one-step hydrothermal route with the help of ethylene glycol. The chem. compn. and structure of the products were confirmed by powder x-ray diffraction, SEM, TEM, and XPS. The cube is composed of nanoparticles with diams. around several dozens of nanometers and the calcination temp. has great influence on the size, the amt. of Cu2O and the surface area of the final products. The gas sensing ability of the as-prepd. porous Cu2O/CuO cubes was investigated toward a series of toxic org. mols., in which the sample calcined at 350° exhibits higher sensing response to acetone. The higher sensing response of this sample might be attributed to the heterostructure of CuO and Cu2O and the relatively high surface area.
    9. 9
      Fan, H.; Yang, L.; Hua, W.; Wu, X.; Wu, Z.; Xie, S.; Zou, B. Controlled synthesis of monodispersed CuO nanocrystals. Nanotechnology 2004, 15, 37– 42,  DOI: 10.1088/0957-4484/15/1/007
      9
      Controlled synthesis of monodispersed CuO nanocrystals
      Fan, Haiming; Yang, Lintao; Hua, Wenshen; Wu, Xingfang; Wu, Zhenyu; Xie, Sishen; Zou, Bingsuo
      Nanotechnology (2004), 15 (1), 37-42CODEN: NNOTER; ISSN:0957-4484. (Institute of Physics Publishing)
      Controlling the size, shape and structure of nanocrystals is technol. important because of the strong effect of size and shape on optical, elec., and catalytic properties. Monodispersed nanocrystals of CuO were prepd. by the pptn.-pyrolysis method. By controlling the starting materials, reactive concn. and annealing temp., the authors can obtain spherical monodispersed CuO nanocrystals of different sizes or rodlike CuO nanocrystals. The particle sizes of CuO monodispersed nanocrystals can be tuned in the range between ∼7 and 30 nm. The products were characterized by x-ray diffraction, TEM, high-resoln. TEM and the UV-visible absorption spectrum. The absorption spectra of CuO nanocrystals show clear evidence of the quantum size effect. The possible formation mechanism of monodispersed CuO nanocrystals is discussed.
    10. 10
      Shui, A.; Zhu, W.; Xu, L.; Qin, D.; Wang, Y. Green sonochemical synthesis of cupric and cuprous oxides nanoparticles and their optical properties. Ceram. Int. 2013, 39, 8715– 8722,  DOI: 10.1016/j.ceramint.2013.04.055
      10
      Green sonochemical synthesis of cupric and cuprous oxides nanoparticles and their optical properties
      Shui, Anze; Zhu, Wenli; Xu, Linfeng; Qin, Dong; Wang, Yanmin
      Ceramics International (2013), 39 (8), 8715-8722CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
      Nanoparticles of CuO and Cu2O with various morphologies were prepd. by a green sonochem. process without any surfactants and templates. The Cu2O nanoparticles with the truncated cubic, cubic octahedral, and octahedral morphologies were prepd. via the deoxidn. of the CuO nanoparticles. The Cu2O and CuO samples were characterized by x-ray diffraction (XRD), SEM, and UV visible absorption spectroscopy (UV-vis). The molar ratio of NaOH to copper sulfate affects the morphol. and size of the CuO and Cu2O nanoparticles produced by the sonication. The band gap energy of CuO nanoparticles was 1.45-1.75 eV, the morphol. had a great effect on the optical properties of CuO. The Cu2O nanoparticles had broad emission peaks at the visible region, and the band gap energy was estd. to be 1.95-2.09 eV. The growth mechanisms of the CuO and Cu2O nanoparticles are discussed.
    11. 11
      Jadhav, S.; Gaikwad, S.; Nimse, M.; Rajbhoj, A. Copper Oxide Nanoparticles: Synthesis, Characterization and Their Antibacterial Activity. J. Cluster Sci. 2011, 22, 121– 129,  DOI: 10.1007/s10876-011-0349-7
      11
      Copper Oxide Nanoparticles: Synthesis, Characterization and Their Antibacterial Activity
      Jadhav, Sunita; Gaikwad, Suresh; Nimse, Madhav; Rajbhoj, Anjali
      Journal of Cluster Science (2011), 22 (2), 121-129CODEN: JCSCEB; ISSN:1040-7278. (Springer)
      Copper oxide nanoparticles were prepd. by electrochem. redn. method using tetra-Bu ammonium bromide (TBAB) as structure directing agent in an org. medium viz. THF and acetonitrile (ACN) in 4:1 ratio by optimizing c.d. and molar concn. of the ligand. The redn. process takes place under inert atm. of nitrogen over a period of 2 h. Such nanoparticles were prepd. using simple electrolysis cell in which the sacrificial anode as a com. available copper metal sheet and platinum (inert) sheet act as a cathode. The parameters such as c.d., solvent polarity, distance between electrodes, and concn. of stabilizers were used to control the size of nanoparticles. The synthesized copper oxide nanoparticles were characterized by using UV-Visible, FTIR, XRD, SEM-EDS and TEM anal. techniques. The nanoparticles were tested for antibacterial activity against human pathogens like Escherichia coli (E. coli) and Staphylococcus strains and which is excellent.
    12. 12
      Borgohain, K.; Murase, N.; Mahamuni, S. Synthesis and properties of Cu2O quantum particles. J. Appl. Phys. 2002, 92, 1292– 1297,  DOI: 10.1063/1.1491020
      12
      Synthesis and properties of Cu2O quantum particles
      Borgohain, Kavita; Murase, Norio; Mahamuni, Shailaja
      Journal of Applied Physics (2002), 92 (3), 1292-1297CODEN: JAPIAU; ISSN:0021-8979. (American Institute of Physics)
      Cuprous oxide quantum particles ≥2 nm (comparable to the Bohr exciton radius) were synthesized using an electrochem. route. Quantum confinement effects are evident from a blueshift in the optical absorption. The optical absorption spectra of Cu2O nanoparticles of different sizes are discussed. Structural anal. by x-ray diffraction as well as electron diffraction shows the nanoparticles to be cubic and single phased Cu2O. x-ray photoelectron spectroscopic studies indicate CuO on the surface of Cu2O core nanoparticles.
    13. 13
      Pandey, P.; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C. Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria. J. Nanopart. Res. 2012, 14, 709  DOI: 10.1007/s11051-011-0709-0
      13
      Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria
      Pandey, Pratibha; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C.
      Journal of Nanoparticle Research (2012), 14 (1), 709/1-709/13CODEN: JNARFA; ISSN:1388-0764. (Springer)
      Copper (II) oxide multi-armed nanoparticles composed of 500-1000 nm long radiating nanospicules with 100-200 nm width near the base and 50-100 nm width at the tapered ends and ∼25 nm thickness were synthesized by electrochem. deposition in the presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphol. and compn., Raman spectroscopy for compd. identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-pos. and -neg. waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano CuO killed 3 × 108 CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 106 CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, resp. Antibacterial activity of nano CuO has been found many-fold compared with com. bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purifn. and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.
    14. 14
      (a) Dagher, S.; Haik, Y.; Ayesh, A. I.; Tit, N. Synthesis andoptical properties of colloidal CuO nanoparticles. J. Lumin. 2014, 151, 149– 154,  DOI: 10.1016/j.jlumin.2014.02.015
      14a
      Synthesis and optical properties of colloidal CuO nanoparticles
      Dagher, Sawsan; Haik, Yousef; Ayesh, Ahmad I.; Tit, Nacir
      Journal of Luminescence (2014), 151 (), 149-154CODEN: JLUMA8; ISSN:0022-2313. (Elsevier B.V.)
      Copper oxide nanoparticles of sizes ranging from 1 to 25 nm were synthesized using a colloid microwave-thermal method, where the av. size of CuO nanoparticles can be tailored by controlled microwave treatment time. The particle size was found to significantly decrease as the microwave processing time increases and can be controlled to have narrow size distributions. Both SEM (SEM) and transmission electron microscopy (TEM) were used to characterize the sizes of the prepd. nanoparticles. The UV-visible absorption spectra of the nanoparticles are blue-shifted with the size redn., and this is attributed to quantum-confinement (QC) effect. Furthermore, the photoluminescence spectra showed UV and visible emissions, and were red shifted with increasing particles size and excitation wavelength. While the former observation confirms the QC effect and corroborates the results of UV-visible absorption spectra, the latter one is attributed to selective near band-edge excitonic transitions assocd. with defect states.
      (b) Wang, Y. X.; Tang, X. F.; Yang, Z. G. A novel wet-chemical method of preparing highly monodispersed Cu2O nanoparticles. Colloids Surf., A 2011, 388, 38– 40,  DOI: 10.1016/j.colsurfa.2011.08.004
      14b
      A novel wet-chemical method of preparing highly monodispersed Cu2O nanoparticles
      Wang, Ying-Xia; Tang, Xiao-Feng; Yang, Zhen-Guo
      Colloids and Surfaces, A: Physicochemical and Engineering Aspects (2011), 388 (1-3), 38-40CODEN: CPEAEH; ISSN:0927-7757. (Elsevier B.V.)
      Highly monodispersed cuprous oxide (Cu2O) nanoparticles, which have a potential application in printed electronics, have been successfully synthesized by a simple wet-chem. route and have been characterized by XRD, HRTEM, UV-vis, and FTIR. The results have shown that the particle size can be controlled by changing the concn. of the stabilizing mol.-oleic acid. Cu2O nanoparticles are spherically shaped with a diam. of about 2 nm and form a face-centered cubic (FCC) crystal structure when the molar ratio of oleic acid to copper precursor is 2. It can be concluded that the Cu2O nanoparticles are capped with oleic acid and polyethylene glycol monododecyl ether. The nano-agglomeration can be filtrated and easily re-dispersed in apolar solvent without ultrasonic method or vigorous stirring.
    15. 15
      (a) Yang, C.; Su, X.; Wang, J.; Cao, X.; Wang, S.; Zhang, L. Facile microwave-assisted hydrothermal synthesis of varied-shaped CuO nanoparticles and their gas sensing properties. Sens. Actuators, B 2013, 185, 159– 165,  DOI: 10.1016/j.snb.2013.04.100
      15a
      Facile microwave-assisted hydrothermal synthesis of varied-shaped CuO nanoparticles and their gas sensing properties
      Yang, Chao; Su, Xintai; Wang, Jide; Cao, Xudong; Wang, Shoujiang; Zhang, Lu
      Sensors and Actuators, B: Chemical (2013), 185 (), 159-165CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
      CuO nanoparticles of varying shape (tadpole-shaped, spindly, leaf/sphere-like and fusiform) were prepd. by a facile microwave-assisted hydrothermal (MH) method. The products were characterized by x-ray diffraction (XRD), FTIR spectroscopy, and TEM. XRD and TEM results revealed pure phase monoclinic CuO nanoparticles with uniform shapes and sizes. FTIR and UV-vis measurements of these nanoparticles with varying shape showed a highly shape-dependent nature. The gas sensing performance of the obtained nanoparticles was analyzed by detection of target gases, including methanol, ethanol, and acetone at 220°. The tadpole-shaped CuO nanoparticles displayed the best response of ≈5 toward 1000 ppm methanol, ≈7 toward 1000 ppm ethanol, and ≈8 toward 800 ppm acetone, resp. All these CuO-based sensors exhibited a relatively higher response to acetone when compared to their response toward methanol and ethanol. The enhanced sensing performance of the tadpole-shaped CuO sensor may be attributed to their unique shape and small size, which is more favorable in rapid and efficient diffusion of org. vapors than the other shaped CuO nanoparticles.
      (b) Wang, H.; Xu, J. Z.; Zhu, J. J.; Chen, H. Y. Preparation of CuO nanoparticles by microwave irradiation. J. Cryst. Growth 2002, 244, 88– 94,  DOI: 10.1016/S0022-0248(02)01571-3
      15b
      Preparation of CuO nanoparticles by microwave irradiation
      Wang, Hui; Xu, Jin-Zhong; Zhu, Jun-Jie; Chen, Hong-Yuan
      Journal of Crystal Growth (2002), 244 (1), 88-94CODEN: JCRGAE; ISSN:0022-0248. (Elsevier Science B.V.)
      CuO nanoparticles with an av. size of ∼4 nm have been successfully prepd. by microwave irradn., using copper(II) acetate and sodium hydroxide as the starting materials and ethanol as the solvent. The CuO nanoparticles are characterized by using techniques such as x-ray powder diffraction, transmission electron microscopy, selected area electron diffraction, XPS and UV-visible absorption spectroscopy. The as-prepd. CuO nanoparticles have regular shape, narrow size distribution and high purity. The band gap is estd. to be 2.43 eV according to the results of the optical measurements of the CuO nanoparticles.
    16. 16
      Sahooli, M.; Sabbaghi, S.; Saboori, R. Synthesis and characterization of mono sized CuO nanoparticles. Mater. Lett. 2012, 81, 169– 172,  DOI: 10.1016/j.matlet.2012.04.148
      16
      Synthesis and characterization of mono-sized CuO nanoparticles
      Sahooli, M.; Sabbaghi, S.; Saboori, R.
      Materials Letters (2012), 81 (), 169-172CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      In this piece of research we have used pptn. method to synthesize CuO nanoparticles. To investigate the characteristics of the CuO nanoparticles, particle size analyzer (PSA), X-ray diffraction technique (XRD), SEM (SEM) and UV-visible absorption spectroscopy were used. To produce nanoparticles with uniform size, we optimized exptl. conditions such as the temp. which was set at 78 °C. The results showed that the synthesized CuO nanoparticles have a suitable dispersion and a thin-size distribution. Also based on the results, the av. size of the nanoparticles was about 4 nm, CuO nanoparticles with various shapes such as clews-like, nanowire, and stretched nanowire-shaped were synthesized by different reaction temps. along with controlled addn. of NaOH, and the surface area was obtained by the BET adsorption method. The max. surface area obtained was 143.7 m2/g which is a considerable surface area.
    17. 17
      (a) Rangel, W. M.; Antunes, R. A.; Gracher, H. A facile method for synthesis of nanostructured copper (II) oxide by coprecipitation. J Mater Res. Technol. 2020, 9, 994– 1004,  DOI: 10.1016/j.jmrt.2019.11.039
      17a
      A facile method for synthesis of nanostructured copper (II) oxide by coprecipitation
      Rangel, Wellington Marques; Boca Santa, Rozineide A. Antunes; Riella, Humberto Gracher
      Journal of Materials Research and Technology (2020), 9 (1), 994-1004CODEN: JMRTAL; ISSN:2238-7854. (Elsevier B.V.)
      Due to their versatility e wide range of phys. and chem. properties, transition metal oxides are very promising as nanostructured materials. Copper oxides are indicated for applications in increasingly wider areas as gas sensing, catalysts, solar cells, electrochromic devices, and antimicrobial materials. In this study, copper (II) oxide nanoparticles were synthesized by the copptn. method from two precursors: copper sulfate and copper chloride. The evaluated precursor concns. were 0.1 M and 0.2 M and temps. were 50 °C and 75 °C. Different results were found, according to synthesis parameters and precursor used. Using copper sulfate as a precursor, a single phase of polycryst. CuO could be obtained, and only a mixt. of cryst. phases of CuO and cllinoatacamite (Cu2(OH)3Cl) were found using copper chloride as the precursor. A known polymorphism phenomenon was obsd. in clinoatacamite according to synthesis reaction parameters, and all three polymorphs were found mixed with CuO nanoparticles. Crystallite sizes of about 10 nm were found in this study, with leaf and rod-like nanostructured particles with dimensions range from 190 to 700 nm, and very good thermal stability. Under the synthesis conditions selected in this study, nanostructured materials made with copper sulfate precursor exhibited smaller crystallite sizes and better thermal stability. The copptn. method used was considered adequate to obtain nanostructured materials, with the advantages of being simple, fast and inexpensive.
      (b) Phiwdang, K.; Suphankij, S.; Mekprasart, W.; Pecharapa, W. Synthesis of CuO Nanoparticles by Precipitation Method Using Different Precursors. Energy Procedia 2013, 34, 740– 745,  DOI: 10.1016/j.egypro.2013.06.808
      17b
      Synthesis of CuO nanoparticles by precipitation method using different precursors
      Phiwdang, Kankanit; Suphankij, Sineenart; Mekprasart, Wanichaya; Pecharapa, Wisanu
      Energy Procedia (2013), 34 (), 740-745CODEN: EPNRCV; ISSN:1876-6102. (Elsevier Ltd.)
      CuO nanoparticles were synthesized by pptn. method using different precursors as copper nitrate (Cu(NO3)2) and copper chloride (CuCl2) with post-heating comparing between as-synthesized and after calcinations. Relevant properties of as-synthesized nanoparticles were investigated by x-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier Transform IR (FTIR) Spectroscopy. Overall results suggest that the formation of CuO nanostructures with different shape, size and morphol. can be achieved using different precursors via this process. The improvement in their crystallinity and purifn. can be further attained by post calcinations process.
      (c) El-Trass, A.; El-Shamy, H.; El-Mehasseb, I.; El-Kema, M. CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids. Appl. Surf. Sci. 2012, 258, 2997– 3001,  DOI: 10.1016/j.apsusc.2011.11.025
      17c
      CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids
      El-Trass, A.; El Shamy, H.; El-Mehasseb, I.; El-Kemary, M.
      Applied Surface Science (2012), 258 (7), 2997-3001CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
      CuO nanoparticles with an av. size of 6 nm were prepd. by an alcothermal method. The prepd. CuO nanoparticles were characterized by x-ray diffraction, TEM, FTIR, and UV-visible absorption spectroscopy. A strong sharp emission under UV excitation is reported from the prepd. CuO nanoparticles. The CuO nanoparticles have high dispersion and narrow size distribution. The fluorescence emission spectra display an intense sharp emission at 365 nm and weak broad intensity emission at 470 nm. Picosecond fluorescence measurements of the nanoparticles suggest bi-exponential function giving time consts. of τ1 (330 ps, 94.21%) and τ 2 (4.69 ns, 5.79%). In neutral and alk. solns., zeta potential values of CuO nanoparticles are neg., due to the adsorption of COO- group via the coordination of bidentate. At low pH the zeta potential value is pos. due to the increased potential of H+ ions in soln. Comparative UV-visible absorption expts. with the model amino acid compds. of pos. and neg. charges as arginine and aspartic acid, resp. confirmed the neg. surface of CuO nanoparticles. The results should be extremely useful for understanding the mode of the interaction with biol. systems. This binding process also affects the particle behavior inside the body.
      (d) Pike, J.; Chan, F. S. W.; Zhang, F.; Wang, X.; Hanson, J. Formation of stable Cu2O from reduction of CuO nanoparticles. Appl. Catal., A 2006, 303, 273– 277,  DOI: 10.1016/j.apcata.2006.02.008
      17d
      Formation of stable Cu2O from reduction of CuO nanoparticles
      Pike, Jenna; Chan, Siu-Wai; Zhang, Feng; Wang, Xianqin; Hanson, Jonathan
      Applied Catalysis, A: General (2006), 303 (2), 273-277CODEN: ACAGE4; ISSN:0926-860X. (Elsevier B.V.)
      In situ time-resolved X-ray diffraction (TR-XRD) using synchrotron radiation has been used to capture the dynamics of the redn. of nanocryst. CuO using a normal supply of CO gas. Copper(II) oxide nanoparticles 4-16 nm in width, as measured by XRD peak broadening, are synthesized using an aq. org.-nitrate method and reduced in isothermal and temp. ramping redn. expts. Temp.-programmed redn. of CuO nanoparticles using a ramping heating profile was obsd. to result in the sequential redn. process CuO → Cu2O → Cu, with CuO reducing completely to the intermediate Cu2O phase before further redn. to metallic copper. Isothermal redn. expts. at 250 °C show that CuO nanoparticles completely reduce to Cu2O, and this phase remains stable without further redn. with continued exposure to CO. In contrast to what is typically obsd. in bulk CuO in both isothermal and ramping redn. conditions, nanocryst. CuO reduces to a stable Cu2O phase rather than forming metallic copper directly. The behavior of the CuO nanoparticles in temp. ramping reducing conditions is controlled by the particle size, with the smaller CuO nanoparticles exhibiting a greater stability and withstanding a higher temp. before their redn. to Cu2O and then to metallic copper nanoparticles.
      (e) Zhu, J.; Li, D.; Chen, H.; Yang, X.; Lu, L.; Wan, X. Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method. Mater. Lett. 2004, 58, 3324– 3327,  DOI: 10.1016/j.matlet.2004.06.031
      17e
      Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method
      Zhu, Junwu; Li, Dan; Chen, Haiqun; Yang, Xujie; Lu, Lude; Wang, Xin
      Materials Letters (2004), 58 (26), 3324-3327CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      Highly dispersed CuO nanoparticles with an av. size of 6 nm were prepd. by a novel quick-pptn. method. The as-prepd. CuO nanoparticles were characterized by x-ray diffraction, TEM, UV-visible absorption spectroscopy, and BET nitrogen adsorption. The as-prepd. CuO nanoparticles have high dispersion and narrow size distribution. The influence of reaction conditions on morphol. of CuO nanocrystals was discussed. Spherical, ellipsoidal, and needle-shaped CuO nanocrystals can be obtained simply by varying the reaction temp. and controlling the addn. of NaOH.
    18. 18
      Yagi, S. Potential-pH Diagrams for Oxidation-State Control of Nanoparticles Synthesized via Chemical Reduction. In Thermodynamics - Physical Chemistry of Aqueous Systems; Moreno-Piraján, J. S., Ed.; InTech: London, 2011; pp 223– 239.
      There is no corresponding record for this reference.
    19. 19
      Arshadi-Rastabi, S.; Moghaddam, J.; Reza, M. Synthesis, characterization and stability of Cu2O nanoparticles produced via supersaturation method considering operational parameters effect. J. Ind. Eng. Chem. 2015, 22, 34– 40,  DOI: 10.1016/j.jiec.2014.06.022
      19
      Synthesis, characterization and stability of Cu2O nanoparticles produced via supersaturation method considering operational parameters effect
      Arshadi-Rastabi, Shahrzad; Moghaddam, Javad; Reza Eskandarian, Mohammad
      Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2015), 22 (), 34-40CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
      Cuprous oxide (Cu2O) nanoparticles have been successfully synthesized using copper acetate as precursor via supersatn. theory as a facile rout. Synthesis parameters, such as the reducing agent concn., reaction temp., reaction time, type of the reducing agent and rate of adding reducing agent were investigated. The exptl. results indicated that size of the Cu2O nanoparticles is dependent on the above mentioned parameters. The Cu2O samples were characterized by X-ray diffraction (XRD), SEM and also by ultra violet visible spectroscopy (UV-vis). Results showed that temp. has unique influence on to the fabrication of Cu2O nanoparticles which illustrate the higher the temp. of the synthesis the smaller the particles would be. Rate of redn. was specified as an influential factor in detg. the particle size distribution. Particles with crystallite size of 74.01 nm were obtained among this study.
    20. 20
      Dodoo-Arhin, D.; Leoni, M.; Scardi, P.; Garnier, E.; Mittiga, A. Synthesis, characterisation and stability of Cu2O nanoparticles produced via reverse micelles microemulsion. Mater. Chem. Phys. 2010, 122, 602– 608,  DOI: 10.1016/j.matchemphys.2010.03.053
      20
      Synthesis, characterisation and stability of Cu2O nanoparticles produced via reverse micelles microemulsion
      Dodoo-Arhin, D.; Leoni, M.; Scardi, P.; Garnier, E.; Mittiga, A.
      Materials Chemistry and Physics (2010), 122 (2-3), 602-608CODEN: MCHPDR; ISSN:0254-0584. (Elsevier B.V.)
      Cuprite (Cu2O) nanoparticles were synthesized at room temp. via redn. of CuCl2·2H2O by NaBH4 in water/n-heptane microemulsion stabilized by the non-ionic Brij30 surfactant. Whole Powder Pattern Modeling of the X-ray diffraction patterns shows the presence of a bimodal size distribution in the nanopowders, with a fraction of domains in the 10-40 nm range and a smaller one below 10 nm. Linear and planar defects are absent. A relationship between the av. size of the larger particles and the quantity of water in the system was obtained. The stability of cuprite under visible light irradn. both during the synthesis and after the prepn. was investigated, showing that a self-catalytic conversion of Cu2O into CuO takes place in water.
    21. 21
      Fan, G.; Li, F. Effect of sodium borohydride on growth process of controlled flower-like nanostructured Cu2O/CuO films and their hydrophobic property. Chem. Eng. J. 2011, 167, 388– 396,  DOI: 10.1016/j.cej.2010.12.090
      21
      Effect of sodium borohydride on growth process of controlled flower-like nanostructured Cu2O/CuO films and their hydrophobic property
      Fan, Guoli; Li, Feng
      Chemical Engineering Journal (Amsterdam, Netherlands) (2011), 167 (1), 388-396CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      In this paper, we report on the three-dimensional nanostructured Cu2O/CuO films with controlled flower-like shapes using a direct crystn. approach in the presence of sodium borohydride without using any performed template, surfactant or oxidant. The microstructures and shapes of Cu2O/CuO architectures were investigated by field emission SEM, X-ray diffraction and transmission electron microscopy. Three types of chrysanthemum-like, candock-like and dandelion-like CuO microstructures consisting of densely packed building blocks of nanobelts or nanoribbons were achieved by governing the concns. of NaBH4. Possible growth mechanisms for the controlled organization of primary building units into three-dimensional flower-like architectures were proposed. After simple surface modification with sodium laurate, the resulting films displayed hydrophobic and even superhydrophobic properties owing to their special surface nano-/microstructures.
    22. 22
      (a) Yuan, L.; Yin, Q.; Wang, Y.; Zhou, G. CuO reduction induced formation of CuO/Cu2O hybrid oxides. Chem. Phys. Lett. 2013, 590, 92– 96,  DOI: 10.1016/j.cplett.2013.10.040
      22a
      CuO reduction induced formation of CuO/Cu2O hybrid oxides
      Yuan, Lu; Yin, Qiyue; Wang, Yiqian; Zhou, Guangwen
      Chemical Physics Letters (2013), 590 (), 92-96CODEN: CHPLBC; ISSN:0009-2614. (Elsevier B.V.)
      Redn. of CuO nanowires results in the formation of a unique hierarchical hybrid nanostructure, in which the parent oxide phase (CuO) works as the skeleton while the lower oxide (Cu2O) resulting from the redn. reaction forms as partially embedded nanoparticles that decorate the skeleton of the parent oxide. Using in situ transmission electron microscopy observations of the redn. process of CuO nanowires, we demonstrate that the formation of such a hierarchical hybrid oxide structure is induced by topotactic nucleation and growth of Cu2O islands on the parent CuO nanowires.
      (b) Srivastava, M.; Singh, J.; Mishra, R. K.; Ojha, A. K. Electro-optical and magnetic properties of monodispersed colloidal Cu2O nanoparticles. J. Alloys Compd. 2013, 555, 123– 130,  DOI: 10.1016/j.jallcom.2012.12.049
      22b
      Electro-optical and magnetic properties of monodispersed colloidal Cu2O nanoparticles
      Srivastava, Manish; Singh, Jay; Mishra, Rajneesh K.; Ojha, Animesh K.
      Journal of Alloys and Compounds (2013), 555 (), 123-130CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      A facile synthesis of colloidal cuprous oxide (Cu2O) nanoparticles was reported via co-pptn. route. Cryst. structure/phase identification, surface morphol., particles size/shape were studied through x-ray diffraction, SEM and TEM techniques, resp. Transmission electron microscope studies reveal that the synthesized nanoparticles are uniform and having spherical shape with av. size of ∼6 nm. The optical properties were probed through FTIR spectroscopy, Raman spectroscopy and UV-visible spectroscopy. Energy band gap studies of the Cu2O nanoparticles reveal the possibility of both, direct and indirect optical transitions. Magnetic properties of the synthesized nanoparticle were measured through vibrating sample magnetometer technique and the obtained result shows that the synthesized nanoparticles possess weak ferromagnetic nature at room temp. Electrochem. response studies of Cu2O/In Sn oxide electrode were carried out using cyclic voltammetry and electrochem. impedance spectroscopy. The electrode prepd. using the colloidal Cu2O nanoparticle shows excellent selectivity and sensitivity for these measurements, which can further be used for an efficient electrochem. based biosensor applications.
      (c) Zhu, J.; Bi, H.; Wang, Y.; Wang, X.; Yang, X.; Lu, L. Solution-phase synthesis of Cu2O cubes using CuO as a precursor. Mater. Lett. 2008, 62, 2081– 2083,  DOI: 10.1016/j.matlet.2007.11.020
      There is no corresponding record for this reference.
    23. 23
      Han, D.; Yang, H.; Zhu, C.; Wang, F. Controlled synthesis of CuO nanoparticles using TritonX-100-based water-in-oil reverse micelles. Powder Technol. 2008, 185, 286– 290,  DOI: 10.1016/j.powtec.2007.10.018
      23
      Controlled synthesis of CuO nanoparticles using TritonX-100-based water-in-oil reverse micelles
      Han, Dongyun; Yang, Huaiyu; Zhu, Chengyun; Wang, Fuhui
      Powder Technology (2008), 185 (3), 286-290CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
      CuO nanoparticles were synthesized by TritonX-100 based water-in-oil reverse micelles system, and characterized by x-ray diffractometer (XRD) and TEM, resp. The grain size, morphol., and distribution were highly dependent on the ratio of water to surfactant (R). The control effect of water content dissolved in reverse micelles was attributed to the enhancement of the exchange rate of reactants among micelles and the relevant change in the interfacial film flexibility of reverse micelles with the increasing amt. of water in the microemulsion.
    24. 24
      Etefagh, R.; Azhir, E.; Shahtahmasebi, N. Synthesis of CuO nanoparticles and fabrication of nanostructural layer biosensors for detecting Aspergillus niger fungi. Sci. Iran. 2013, 20, 1055– 1058,  DOI: 10.1016/j.scient.2013.05.015
      There is no corresponding record for this reference.
    25. 25
      Liu, X.; Geng, B.; Du, Q.; Ma, J.; Liu, X. Temperature-controlled self-assembled synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route. Mater. Sci. Eng., A 2007, 448, 7– 14,  DOI: 10.1016/j.msea.2006.08.104
      25
      Temperature-controlled self-assembled synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route
      Liu, Xiaowang; Geng, Baoyou; Du, Qingbo; Ma, Jinzhu; Liu, Xianming
      Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing (2007), A448 (1-2), 7-14CODEN: MSAPE3; ISSN:0921-5093. (Elsevier B.V.)
      In this paper, we report on the synthesis of CuO, Cu2O and Cu nanoparticles through a single-precursor route by controlling the growth temp. CuO and Cu2O nanoparticles have nanoporous structural configurations composed of a large no. of primary particles. According to the difference between the crystal planes, we proposed the possible growth mechanisms of CuO, Cu2O and Cu nanoparticles. Selective adsorption of oleylamine on various crystal planes may play an important role in the growth process. The understanding of this self-assembling process will help us to develop reliable and reproducible methods to synthesis other three dimensional nanostructured architectures and increase the knowledge of self-assembly.
    26. 26
      Lee, W.; Piao, L.; Park, C.; Lim, Y.; Do, Y.; Yoon, S.; Kim, S.-H. Facile synthesis and size control of spherical aggregates composed of Cu2O nanoparticles. J. Colloid Interface Sci. 2010, 342, 198– 201,  DOI: 10.1016/j.jcis.2009.10.027
      26
      Facile synthesis and size control of spherical aggregates composed of Cu(2)O nanoparticles
      Lee Woo-Ram; Piao Longhai; Park Cheol-Hee; Lim Young Soo; Do Young Rag; Yoon Sungho; Kim Sang-Ho
      Journal of colloid and interface science (2010), 342 (1), 198-201 ISSN:.
      The secondary structures of Cu(2)O nanoparticles were prepared in aqueous solution utilizing self-assembled aggregation process. By introducing polyacrylamide (PAM) as a secondary surfactant, the colloidal nanoparticle aggregates (CNAs) become uniform in size and exhibit spherical shape compared to the random aggregates without PAM. The size of CNA can be systematically controlled from 300nm to 1000nm by varying PAM concentration. The formation mechanism was explained based on a conventional colloidal particle formation mechanism. These control methods may generally be applied to the preparation of secondary nanoparticle structures.
    27. 27
      (a) Siddiqi, K. S.; Husen, A. Current status of plant metabolite-based fabrication of copper/copper oxide nanoparticles and their applications: a review. Biomater. Res. 2020, 24, 11  DOI: 10.1186/s40824-020-00188-1
      27a
      Current status of plant metabolite-based fabrication of copper/copper oxide nanoparticles and their applications: a review
      Siddiqi, Khwaja Salahuddin; Husen, Azamal
      Biomaterials Research (2020), 24 (1), 11CODEN: BRIEFJ; ISSN:2055-7124. (BioMed Central Ltd.)
      A review. Abstr.: Since green mode of nanoparticles (NPs) synthesis is simple, advantageous and environment friendly relative to chem. and phys. procedures, various plant species have been used to fabricate copper and copper oxide nanoparticles (Cu/CuO-NPs) owing to the presence of phytochems. which often act as capping as well as stabilizing agent. These Cu/CuO-NPs are highly stable and used in the degrdn. of org. dyes like methylene blue and redn. of org. compds. such as phenols. They are also used as antibacterial, antioxidant and antifungal agent due to their cytotoxicity. They are also examd. for agricultural crops growth and productivity. Cu-NPs increased the root and shoot growth of mung bean. In wheat plants, these particles reduced shoot growth; and enhanced the grain yield and stress tolerance through starch degrdn. Similarly, CuO-NPs treated seedlings have shown reduced chlorophyll, carotenoid and sugar content, whereas proline and anthocyanins were increased in Brassica rapa seedlings. Overall, this review presents the recent understanding of plant-mediated Cu and CuO-NPs fabrication and their application in biomedicine, environmental remediation and agricultural practices. A comparison of the traditional/conventional method of fabrication of NPs with those of green protocols has also been made. Some misconception of copper chem. has also been critically discussed in terms of oxidn. and redn. reactions.
      (b) Ananda, H. C.; Desalegn, T.; Kassa, M.; Abebe, B.; Assefa, T. Synthesis of Green Copper Nanoparticles Using Medicinal Plant Hagenia abyssinica (Brace) JF. Gmel. Leaf Extract: Antimicrobial Properties. J. Nanomater. 2020, 1– 12,  DOI: 10.1155/2020/3924081
      There is no corresponding record for this reference.
      (c) Keabadile, O. P.; Aremu, A. O.; Elugoke, S. E.; Fayemi, O. E. Green and Traditional Synthesis of Copper Oxide Nanoparticles-Comparative Study. Nanomaterials 2020, 10, 2502  DOI: 10.3390/nano10122502
      27c
      Green and traditional synthesis of copper oxide nanoparticles-comparative study
      Keabadile, Obakeng P.; Aremu, Adeyemi O.; Elugoke, Saheed E.; Fayemi, Omolola E.
      Nanomaterials (2020), 10 (12), 2502CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
      The current study compared the synthesis, characterization and properties of copper oxide nanoparticles (CuO) based on green and traditional chem. methods. The synthesized CuO were confirmed by spectroscopic and morphol. characterization such as UV-visible (UV-vis) spectroscopy, fourier transform IR (FTIR) spectroscopy, zeta potential, SEM (SEM) and energy dispersed X-ray (EDX). Electrochem. behavior of the modified electrodes was done using cyclic voltammetry (CV) in ferricyanide/ferrocyanide ([Fe(CN)6]4-/[Fe(CN)6]3-) redox probe. As revealed by UV spectrophotometer, the absorption peaks ranged from 290-293 nm for all synthesized nanoparticles. Based on SEM images, CuO were spherical in shape with agglomerated particles. Zeta potential revealed that the green CuO have more neg. surface charge than the chem. synthesized CuO. The potential of the green synthesized nanoparticles was higher relative to the chem. synthesized one. Cyclic voltammetry studies indicated that the traditional chem. synthesized CuO and the green CuO have electrocatalytic activity toward the ferricyanide redox probe. This suggests that the green CuO can be modified with other nanomaterials for the prepn. of electrochem. sensors toward analytes of interest.
    28. 28
      Ganga, B. G.; Santhosh, P. N. Manipulating aggregation of CuO nanoparticles: Correlation between morphology and optical properties. J. Alloys Compd. 2014, 612, 456– 464,  DOI: 10.1016/j.jallcom.2014.05.171
      28
      Manipulating aggregation of CuO nanoparticles: Correlation between morphology and optical properties
      Ganga, B. G.; Santhosh, P. N.
      Journal of Alloys and Compounds (2014), 612 (), 456-464CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      Controlled synthesis of CuO nanoparticles with various morphologies were achieved by a wet chem. method by the redn. of copper acetate with NaOH. Influence of surfactant, alk. concn. and solvent medium on the morphol. of nanoparticles was investigated. Our studies reveal that these parameters alter the aggregation-growth processes and hence the morphol. Sodium dodecyl sulfate (SDS) as a structure-guiding agent has a strong impact on the morphol. of nanostructure. By adjusting the rate of hydrolysis, two dimensional netted structures consisting of bundles of nanorods were obtained, formed by oriented attachment mechanism. Moreover, well defined and dispersed CuO nanoparticles were produced by manipulating the solvent medium. Optical properties were studied using UV-Vis absorption and Raman spectroscopy. Morphol. and size of nanoparticles have a profound effect on the nature of multi-phonon band obsd. in the Raman spectra of CuO nanostructures.
    29. 29
      Rao, M. P.; Anandan, S.; Suresh, S.; Asiri, A. M.; Wu, J. J. Surfactant Assisted Synthesis of Copper Oxide Nanoparticles for Photocatalytic Degradation of Methylene Blue in the Presence of Visible Light. Energy Environ. Focus 2015, 4, 250– 255,  DOI: 10.1166/eef.2015.1168
      There is no corresponding record for this reference.
    30. 30
      Reddy, S.; Kumara Swamy, B. E.; Jayadevappa, H. CuO nanoparticle sensor for the electrochemical determination of dopamine. Electrochim. Acta 2012, 61, 78– 86,  DOI: 10.1016/j.electacta.2011.11.091
      30
      CuO nanoparticle sensor for the electrochemical determination of dopamine
      Reddy, Sathish; Kumara Swamy, B. E.; Jayadevappa, H.
      Electrochimica Acta (2012), 61 (), 78-86CODEN: ELCAAV; ISSN:0013-4686. (Elsevier Ltd.)
      Different shaped CuO nanoparticles were synthesized using cetyl tri-Me ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) in a co-pptn. method. The CuO nanoparticles were characterized using XRD, SEM, TEM, IR absorption spectroscopy (IR) and UV-visible absorption spectroscopy (UV-visible). The prepd. CuO nanoparticles were used for the prepn. of modified carbon-paste electrodes (MCPE) for the electrochem. detection of dopamine (DA) at pH 6.0. The MCPE prepd. from flake-shaped CuO nanoparticles exhibited an enhanced current response for DA. Electrochem. parameters, such as the surface area of the electrode, the heterogeneous rate const. (ks) and the lower detection limit (5.5 × 10-8 M), were calcd. and compared with those of the MCPE prepd. from rod-shaped CuO nanoparticles. The MCPE prepd. from SDS/polyglycine/flake-shaped CuO nanoparticles exhibited a further improved current response for DA and a high selectivity (E AA - E DA = 0.28 V) for the simultaneous study of DA and ascorbic acid (AA) at pH 6.0. The modified carbon-paste electrochem. sensors were compared, and the MCPE prepd. from SDS/polyglycine/flake-shaped CuO nanoparticles exhibited better performance than the MCPE prepd. from CTAB/polyglycine/flake-shaped CuO nanoparticles.
    31. 31
      Namburu, P. K.; Kulkarni, D. P.; Misra, D.; Das, D. K. Viscosity of copper oxide nanoparticles dispersed in ethylene glycol and water mixture. Exp. Therm. Fluid Sci. 2007, 32, 397– 402,  DOI: 10.1016/j.expthermflusci.2007.05.001
      31
      Viscosity of copper oxide nanoparticles dispersed in ethylene glycol and water mixture
      Namburu, Praveen K.; Kulkarni, Devdatta P.; Misra, Debasmita; Das, Debendra K.
      Experimental Thermal and Fluid Science (2007), 32 (2), 397-402CODEN: ETFSEO; ISSN:0894-1777. (Elsevier B.V.)
      Nanofluids are new kinds of fluids engineered by dispersing nanoparticles in base fluids. This paper presents an exptl. investigation of rheol. properties of copper oxide nanoparticles suspended in 60:40 (by wt.) ethylene glycol and water mixt. Nanofluids of particle vol. percentage ranging from 0% to 6.12% were tested. The expts. were carried over temps. ranging from -35 °C to 50 °C to demonstrate their applicability in cold regions. For the particle vol. concns. tested, nanofluids exhibited Newtonian behavior. An exptl. correlation was developed based on the data, which relates viscosity with particle vol. percent and the nanofluid temp.
    32. 32
      Siddiqui, H.; Qureshi, M. S.; Haque, F. Z. Preparation of silver nanoparticles by laser ablation in polyvinylpyrrolidone solutions nanostructures and their spectroscopic analysis. Optik 2016, 127, 2740– 2747,  DOI: 10.1016/j.ijleo.2015.11.220
      32
      Surfactant assisted wet chemical synthesis of copper oxide (CuO) nanostructures and their spectroscopic analysis
      Siddiqui, Hafsa; Qureshi, M. S.; Haque, Fozia Z.
      Optik (Munich, Germany) (2016), 127 (5), 2740-2747CODEN: OTIKAJ; ISSN:0030-4026. (Elsevier GmbH)
      CuO nanocrystals and their nanoarchitectures with various morphologies were constructed via a simple surfactant-assisted wet chem. process. The introduction of sodium dodecyl sulfate (SDS) as anionic surfactant, cetyltrimethylammonium bromide (CTAB) as cationic surfactant and polyethylene glycol (PEG) as nonionic surfactant leads to the formation of cube, leaf and flower-like CuO nanostructures, resp. The prepd. samples were characterized by different characterization techniques such as X-ray diffraction (XRD), SEM (SEM), Fourier transform IR (FT-IR) spectroscopy, Raman, UV-visible diffused reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. Different spectroscopic results revealed that all the samples have cryst. single-phase CuO monoclinic structures. The av. crystallite size for SDS, PEG and CTAB assisted CuO samples are around 20 nm, 19 nm and 16 nm resp. It was obsd. that the size and shape of particle is affected by the nature of surfactant. Addnl., in all the samples, Raman and FTIR spectra shows three identical Cu-O vibration modes that indicate the presence of cryst. CuO monoclinic structure. Diffuse reflectance results revealed that the addn. of surfactants significantly enhanced the optical bandgap value from 1.40 eV to 1.54 eV, due to quantum confinement effect. Photoluminescence (PL) spectra showed both UV as well as visible emission peaks indicating their good optical properties. The presence of strong visible light absorption in all the samples revealed that it can be used as absorbing material in solar cell.
    33. 33
      Mayekar, J.; Dhar, V.; Radha, S. Synthesis of Copper Oxide Nanoparticles Using Simple Chemical Route. Int. J. Sci. Eng. Res. 2014, 5, 928– 930
      There is no corresponding record for this reference.
    34. 34
      Zhang, H.; Ren, X.; Chi, Z. (2007) Shape-controlled synthesis of Cu2O nanocrystals assisted by PVP and application as catalyst for synthesis of carbon nanofibers. J. Cryst. Growth 2007, 304, 206– 210,  DOI: 10.1016/j.jcrysgro.2007.01.043
      34
      Shape-controlled synthesis of Cu2O nanocrystals assisted by PVP and application as catalyst for synthesis of carbon nanofibers
      Zhang, Hui; Ren, Xue; Cui, Zuolin
      Journal of Crystal Growth (2007), 304 (1), 206-210CODEN: JCRGAE; ISSN:0022-0248. (Elsevier B.V.)
      In this paper, cuprous oxide (Cu2O) nanostructures with different shapes, such as spheres, cubes and rods, have been synthesized by reducing copper nitrate trihydrate with ethylene glycol in the present of poly(vinylpyrrolidone) (PVP). The molar ratio of PVP (in the repeating unit)/Cu(NO3)2·3H2O and reaction temp. have significant effects on the formation and growth of these Cu2O nanostructures. The Cu2O nanorods were fabricated at the molar ratios of PVP/Cu(NO3)2·3H2O 2-3, while spherical and cubic nanoparticles were formed at the ratios of PVP/Cu(NO3)2·3H2O 5-7 and 10-15. Increasing with reaction temps., monodisperse particles were obtained. The as-synthesized nanoparticles and nanorods were investigated by transmission electron microscopy (TEM), and field emission SEM (FE-SEM) and X-ray diffractometry (XRD). With the as-prepd. nanoparticles as catalyst, carbon nanofibers (CNFs) were synthesized by catalytic polymn. of acetylene at a lower temp. (250 °C). The effects of the catalyst particle sizes on the morphologies of the carbon fibers were studied.
    35. 35
      Liu, P.; Li, Z.; Cai, W.; Fang, M.; Luo, X. Fabrication of cuprous oxide nanoparticles by laser ablation in PVP aqueous solution. RSC Adv. 2011, 1, 847– 851,  DOI: 10.1039/c1ra00261a
      35
      Fabrication of cuprous oxide nanoparticles by laser ablation in PVP aqueous solution
      Liu, Peisheng; Li, Zhigang; Cai, Weiping; Fang, Ming; Luo, Xiangdong
      RSC Advances (2011), 1 (5), 847-851CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      The cuprous oxide nanoparticles have been fabricated through pulsed laser ablation of copper target in PVP aq. soln. The structure, morphol. and compn. of the nanoparticles have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resoln. TEM (HRTEM), XPS and X-ray excited auger spectra (XAES). The results show that the mean size of the as-prepd. in diam. is about 29 nm with a relative narrow size distribution and samples are polycrystal Cu2O nanoparticles with a shell of thin layer of amorphous CuO. Furthermore, a possible mechanism for formation of such the cuprous oxide nanoparticles is discussed. We concluded that pulsed laser ablation of copper in liq. is a feasible method for the synthesis of cuprous oxide nanoparticles.
    36. 36
      Qiang, A.-H.; Zhao, L.-M.; Xu, C.-J.; Zhou, M. Effect of Dispersant on the Colloidal Stability of Nano-sized CuO Suspension. J. Dispersion Sci. Technol. 2007, 28, 1004– 1007,  DOI: 10.1080/01932690701522293
      36
      Effect of dispersant on the colloidal stability of nano-sized CuO suspension
      Qiang, Ai-Hong; Zhao, Li-Ming; Xu, Chun-Jian; Zhou, Ming
      Journal of Dispersion Science and Technology (2007), 28 (7), 1004-1007CODEN: JDTEDS; ISSN:0193-2691. (Taylor & Francis, Inc.)
      The stabilization of nanosized CuO suspensions was examd. to look for the primary mechanism of dispersion. The dispersion stability of suspension was characterized by sedimentation tests, zeta potential, granularity tests, and IR spectroscopy (IR). Influence factors such as pH and the concn. of the dispersant on the colloidal stability of the suspension were investigated. Sodium polyacrylate was fit to stabilize the suspension of CuO nanoparticles through electrosteric repulsion. Also, smaller viscosity and better dispersion effects were achieved when sodium polyacrylate mass fraction was 0.4-0.8% (based on the powder), pH was 10.
    37. 37
      (a) Liu, Q. M.; Zhou, D. B.; Yamamoto, Y.; Ichino, R.; Okido, M. Preparation of Cu nanoparticles with NaBH4 by aqueous reduction method. Trans. Nonferrous Met. Soc. China 2012, 22, 117– 12,  DOI: 10.1016/S1003-6326(11)61149-7
      37a
      Preparation of Cu nanoparticles with NaBH4 by aqueous reduction method
      Liu, Qing-ming; Zhou, De-bi; Yuya, Yamamoto; Ryoichi, Ichino; Masazumi, Okido
      Transactions of Nonferrous Metals Society of China (2012), 22 (1), 117-123CODEN: TNMCEW; ISSN:1003-6326. (Elsevier B.V.)
      Cu nanoparticles were prepd. by reducing Cu2+ ions with NaBH4 in alk. soln. The effects of NaBH4 concn. and dripping rate on the formation of Cu nanoparticles were studied. The optimum conditions are found to be 0.2 mol/L Cu2+, soln. with pH = 12, temp. of 313 K and 1% gelatin as dispersant, to which 0.4 mol/L NaBH4 is added at a dripping rate of 50 mL/min. NH3 · H2O is found to be the optimal complexant to form the Cu precursor. A series expts. were conducted to study the reaction process at different time points.
      (b) Lu, Y.; Wei, W.; Chen, W. Copper nanoclusters: Synthesis, characterization and properties. Chin. Sci. Bull. 2012, 57, 41– 47,  DOI: 10.1007/s11434-011-4896-y
      37b
      Copper nanoclusters: Synthesis, characterization and properties
      Lu, Yi Zhong; Wei, Wen Tao; Chen, Wei
      Chinese Science Bulletin (2012), 57 (1), 41-47CODEN: CSBUEF; ISSN:1001-6538. (Springer)
      A review. Metal nanoclusters with a core size smaller than 2 nm have attracted much attention because of their unique phys. and chem. properties. Among the studied metal nanoclusters, gold and silver have been studied extensively by size-controlled synthesis, structural characterization and properties investigations. Recently, considerable research effort has been devoted to the investigation of copper nanoclusters. In this review, we highlight recent progress in the study of copper nanoclusters in terms of synthesis methods, characterization techniques and their novel optical and catalytic properties.
    38. 38
      Zhao, H.; Yang, J.; Wang, L.; Tian, C.; Jiangaand, B.; Fu, H. Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid. Chem. Commun. 2011, 47, 2014– 2016,  DOI: 10.1039/c0cc04432f
      38
      Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid
      Zhao, Hong; Yang, Jun; Wang, Lei; Tian, Chungui; Jiang, Baojiang; Fu, Honggang
      Chemical Communications (Cambridge, United Kingdom) (2011), 47 (7), 2014-2016CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Small and highly dispersed Pd nanoparticles supported on graphene nanosheets were fabricated via a strategy of etching a Cu template with Pd2+. The obtained hybrid exhibited significant catalytic activity for formic acid oxidn.
    39. 39
      (a) Fanning, J. C.; Brooks, B. C.; Hoeglund, A. B.; Pelletier, D. A.; Wadford, J. A. The reduction of nitrate and nitrite ions in basic solution with sodium borohydride in the presence of copper(II) ions. Inorg. Chim. Acta 2000, 310, 115– 119,  DOI: 10.1016/S0020-1693(00)00262-0
      39a
      The reduction of nitrate and nitrite ions in basic solution with sodium borohydride in the presence of copper(II) ions
      Fanning, James C.; Brooks, Benjamin C.; Hoeglund, Adrienne B.; Pelletier, Daryl A.; Wadford, Julie A.
      Inorganica Chimica Acta (2000), 310 (1), 115-119CODEN: ICHAA3; ISSN:0020-1693. (Elsevier Science S.A.)
      The reaction of NaNO3 and NaBH4 with added Cu(OH)2 in 1 M NaOH at 65° under Ar rapidly produced NH3, Cu metal, and H2 with NO2- formed as an intermediate. The overall equation describing the reaction is: Cu(OH)2 + 3NO3- + 7BH4- + 20H2O → Cu + 3NH3 + 7B(OH)4- + 15H2 + 3OH-. A direct reaction of NaNO2 with NaBH4 under the same conditions as those used with NaNO3 follows the equation: Cu(OH)2 + NO2- + 2BH4- + 5H2O → Cu + 4H2 + NH3 + 2B(OH)4- + OH-. The redns. of nitrate and nitrite with NaBH4 did not take place in basic soln. unless Cu(OH)2 was present. The NO3-/BH4- reaction was studied in basic medium since nuclear waste is basic (pH ≈ 14), and since NaBH4 is safely handled and stored in basic soln. Also, having borate ion, a potential glass-former, as a product in the elimination of nitrate from waste would be an advantage.
      (b) Gómez-Lahoz, C.; Garcia-Herruzo, F.; Rodriguez-Maroto, J. M.; Rodriguez, J. J. Cobalt (II) removal from water by chemical reduction with sodium borohydride. Water Res. 1993, 27, 985– 992,  DOI: 10.1016/0043-1354(93)90062-M
      39b
      Cobalt(II) removal from water by chemical reduction with sodium borohydride
      Gomez-Lahoz, C.; Garcia-Herruzo, F.; Rodriguez-Maroto, J. M.; Rodriguez, J. J.
      Water Research (1993), 27 (6), 985-92CODEN: WATRAG; ISSN:0043-1354.
      The stoichiometry and kinetics of Co2+ redn. with NaBH4 in aq. soln. were studied. An excess of borohydride is needed to complete Co2+ removal from wastewater. In this case, Co ppts. mainly as Co(OH)2. Absence of dissolved O in the reactor is required to avoid rapid reoxidn. of reduced Co. The elemental anal. of the reduced species is consistent with Co2B. The ease of sludge reoxidn. and the final B concn. in the effluent resulting from the needed borohydride excess are serious disadvantages of this technique to remove Co2+. A kinetic model was proposed to describe the behavior of the system. The model reproduces reasonably well exptl. results, although some discrepancies were obsd. in the early stages of the process. These can be mainly attributed to mass-transfer limitations.
    40. 40
      Burriel, F.; Lucena, F.; Arribas, S.; Hernández, J. Reacciones de oxido-reducción. In Química Analítica Cuantitativa [Qualitative Analytical Chemistry], 18th ed.; Thomson Paraninfo: Madrid, 2006; pp 175– 234.
      There is no corresponding record for this reference.
    41. 41
      Chen, D.; Ni, S.; Fang, J. J.; Xiao, T. Preparation of Cu2O nanoparticles in cupric chloride solutions with a simple mechanochemical approach. J. Alloys Compd. 2010, 504, S345– S348,  DOI: 10.1016/j.jallcom.2010.02.138
      41
      Effects of strontium on microstructure and mechanical properties of as-cast Mg-5 wt.%Sn alloy
      Liu, Hongmei; Chen, Yungui; Zhao, Haofeng; Wei, Shanghai; Gao, Wei
      Journal of Alloys and Compounds (2010), 504 (2), 345-350CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      The Sr addn. to the Mg-5 wt.%Sn alloy results in grain refinement and the formation of a rod-shaped and a bone-shaped MgSnSr intermetallic phase which is mainly located on the grain boundaries. The yield strength is improved, while the tensile strength and elongation first increased, and then decreased with a large addn. of Sr. Optimum mech. properties at ambient temp. are obtained for the alloy with 2.14 wt. %Sr. Tensile properties of the alloys at elevated temps. are also improved, and the decrease in strength at elevated temp. slowed down with increasing Sr addn., indicating that Sr can improve the thermal stability of Mg-Sn alloys.
    42. 42
      Cudennec, Y.; Lecerf, A. The transformation of Cu(OH)2 into CuO, revisited. Solid State Sci. 2003, 5, 1471– 1474,  DOI: 10.1016/j.solidstatesciences.2003.09.009
      42
      The transformation of Cu(OH)2 into CuO, revisited
      Cudennec, Yannick; Lecerf, Andre
      Solid State Sciences (2003), 5 (11-12), 1471-1474CODEN: SSSCFJ; ISSN:1293-2558. (Elsevier SAS)
      Cu(OH)2 is metastable. It easily transforms into more stable CuO, either in the solid state by a thermal dehydration or at room temp., in aq. basic solns. In the solid state, the transformation was performed at a relatively low temp., 423 K. It is a topotactic or a pseudomorphic transformation owing to clear relations between axes of the two solids, in the three directions. The reacting process is described and the corresponding vectorial relations between crystal parameters are proposed. It is not the same case in aq. basic solns. Cu(OH)2 gives rise to CuO through the formation of a complex anion, Cu(OH)42-, by a reconstructive transformation involving a dissoln. reaction followed by a pptn.
    43. 43
      (a) Shahmiri, M.; Ibrahim, N. A.; Zainuddin, N.; Asim, N.; Bakhtyar, B.; Zaharim, A.; Sopian, K. Effect of pH on the Synthesis of CuO Nanosheets by Quick Precipitation Method. WSEAS Trans. Environ. Dev. 2013, 2, 137– 146
      There is no corresponding record for this reference.
      (b) Shahmiri, M.; Ibrahim, N. A.; Shayesteh, F.; Asim, N.; Motallebi, N. Preparation of PVP-coated copper oxide nanosheets as antibacterial and antifungal agents. J. Mater. Res. 2013, 28, 3109– 3118,  DOI: 10.1557/jmr.2013.316
      43b
      Preparation of PVP-coated copper oxide nanosheets as antibacterial and antifungal agents
      Shahmiri, Mahdi; Ibrahim, Nor Azowa; Shayesteh, Fatemeh; Asim, Nilofar; Motallebi, Nabi
      Journal of Materials Research (2013), 28 (22), 3109-3118CODEN: JMREEE; ISSN:2044-5326. (Cambridge University Press)
      Copper oxide (CuO) nanosheets synthesized in polyvinylpyrrolidone (PVP) were characterized with respect to antimicrobial activity by quick pptn. method. Different sizes and shapes of CuO nanosheets were obtained by simple variations of PVP concns. The x-ray diffraction results revealed the formation of pure-phase CuO with monoclinic structure. Transmission electron microscopy anal. showed that the av. ratio of length to width of these nanosheets increased with increasing PVP concns. Due to the quantum size effect, CuO nanosheets exhibit a blue shift in the UV-visible spectra. Field emission SEM results showed that as the concn. of PVP increased, well-defined morphologies were formed on the surface of the products. Energy dispersive anal. of x-ray clearly confirmed the presence of Cu and O with an at. ratio of 1:1. Fourier transform IR spectroscopy results showed that C=O in PVP coordinated with CuO and formed a protective layer. The mechanism of the reaction was also discussed. CuO nanosheets in suspension showed activity against a range of bacterial pathogens and fungi with min. bactericidal concns. (MBCs) ranging from 100 to 5000 μg/mL. The extent of the inhibition zones and the MBCs was found to be size-dependent.
    44. 44
      Zhang, J.; Liu, J.; Peng, Q.; Wang, X.; Li, Y. Nearly Monodisperse Cu2O and CuO Nanospheres: Preparation and Applications for Sensitive Gas Sensors. Chem. Mater. 2006, 18, 867– 871,  DOI: 10.1021/cm052256f
      44
      Nearly Monodisperse Cu2O and CuO Nanospheres: Preparation and Applications for Sensitive Gas Sensors
      Zhang, Jiatao; Liu, Junfeng; Peng, Qing; Wang, Xun; Li, Yadong
      Chemistry of Materials (2006), 18 (4), 867-871CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      A low-temp. soln.-phase method for prepg. nearly monodisperse Cu2O and CuO nanospheres is presented. The rapid prodn. of supersatd. Cu2O nanocrystals and their regular spherical aggregation lead to the monodispersity of Cu2O nanospheres. By modulating the concn. of reactant H2O, the diam., crystn., and monodispersity of Cu2O nanospheres can be kinetically controlled. Because the thin films prepd. by as-obtained Cu2O nanospheres have large surface areas and plentiful spaces to interact with gases, the gas sensors based on as-prepd. Cu2O nanospheres have high sensitivity and good selectivity to some flammable gases. The surface modification with noble metals or n-type metal oxides based on obtained nanospheres will be helpful to enrich their sensor applications.
    45. 45
      (a) La Mer, V. K. Nucleation in Phase Transitions. Ind. Eng. Chem. 1952, 44, 1270– 1277,  DOI: 10.1021/ie50510a027
      45a
      Kinetics in phase transitions
      LaMer, Victor K.
      Industrial and Engineering Chemistry (1952), 44 (), 1270-7CODEN: IECHAD; ISSN:0019-7866.
      A detailed review of conceptual and phenomenological aspects of nucleation processes including the historical development, Ostwald's clarifying views, the Volmer extension of Gibbs' fundamental equations for the work involved in forming a new phase, the statistical approach to the characterization and work of formation of embryos and nuclei, the rate of nucleus formation, heterogeneous nucleation and the application to the stability of polydisperse colloidal dispersions, the prepn. of monodisperse aerosols and hydrosols, and the time lag in the supersatn. of BaSO4.
      (b) La Mer, V. K.; Dinegar, R. H. Theory, Production and Mechanism of Formation of Monodispersed Hydrosols. J. Am. Chem. Soc. 1950, 72, 4847– 4854,  DOI: 10.1021/ja01167a001
      45b
      Theory, production, and mechanism of formation of monodispersed hydrosols
      La Mer, Victor K.; Dinegar, Robert H.
      Journal of the American Chemical Society (1950), 72 (), 4847-54CODEN: JACSAT; ISSN:0002-7863.
      Monodispersed colloids exhibiting higher-order Tyndall spectra were prepd. by pptn. of S8 from EtOH and Me2CO solns. by the careful addn. of H2O. The relation between the concn. of S and the vol. fraction of H2O at the crit. point of S-EtOH-H2O solns. was investigated. Sols prepd. by this diln. method were investigated as to dispersion of wave length in their angular scattering of visible light and their transmission as a function of wave length. The size, no., and charge of the particles of such sols are in the same range as those prepd. by the acid decompn. of Na2S2O3. The rates of growth of sols prepd. by such a diln. method were investigated. The growth rates obtained were reproduced from theoretical considerations that allow the estn. of the value of the diffusion coeff. of S8 in EtOH-H2O and Me2CO-H2O mixts. The value of this diffusion coeff. lies in the range 7 to 8 × 10-6 cm.2/sec. for both media. The application of this method for estg. diffusion coeffs. is valid for any colloidal system that is characterized by a small particle-size distribution at all stages of its growth. A qual. explanation is offered for the necessary conditions under which monodispersed colloids can be prepd. for both the diln. and acid-decompn.-of-Na2S2O3 methods.
    46. 46
      Thanh, N. T. K.; Maclean, N.; Mahiddine, S. Mechanisms of Nucleation and Growth of Nanoparticles in Solution. Chem. Rev. 2014, 114, 7610– 7630,  DOI: 10.1021/cr400544s
      46
      Mechanisms of Nucleation and Growth of Nanoparticles in Solution
      Thanh, Nguyen T. K.; MacLean, N.; Mahiddine, S.
      Chemical Reviews (Washington, DC, United States) (2014), 114 (15), 7610-7630CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. This work covers the area of crystal growth of nanoparticles in soln. The authors first discuss classical crystal growth and crystal nucleation and the formation of particle size distribution. They then continue the discussion of crystal growth with the coverage of the theories of the LaMer Mechanism, Ostwald Ripening, Digestive Ripening, Finke-Watzky two step mechanism, coalescence and orientated attachment, and intraparticle growth. They then discuss literature examples of nanoparticle formation of copper, silver, and gold noble metals, and metal oxides. The use of nanoparticle formation for the formation of quantum dots are also given.
    47. 47
      Zhang, X.; Xie, Y.; Xu, F.; Liu, X.; Xu, D. Shape-controlled synthesis of submicro-sized cuprous oxide octahedra. Inorg. Chem. Commun. 2003, 6, 1390– 1392,  DOI: 10.1016/j.inoche.2003.09.002
      47
      Shape-controlled synthesis of submicro-sized cuprous oxide octahedra
      Zhang, Xu; Xie, Yi; Xu, Fen; Liu, Xiaohui; Xu, Di
      Inorganic Chemistry Communications (2003), 6 (11), 1390-1392CODEN: ICCOFP; ISSN:1387-7003. (Elsevier Science B.V.)
      Monodisperse submicro-sized cuprous oxide (Cu2O) octahedra are successfully prepd. in large quantities assisted by the capping reagent poly(vinyl pyrrolidone) (PVP-K30, MW = 58,000) and the formation mechanism of Cu2O octahedra is analyzed.
    48. 48
      Guzman, A.; Arroyo, J.; Verde, L.; Rengifo, J. Synthesis and characterization of copper nanoparticles/polyvinyl chloride (Cu NPs/PVC) nanocomposites. Procedia Mater. Sci. 2015, 9, 298– 304,  DOI: 10.1016/j.mspro.2015.04.038
      48
      Synthesis and characterization of copper nanoparticles/polyvinyl chloride (Cu NPs/PVC) nanocomposites
      Guzman, A.; Arroyo, J.; Verde, L.; Rengifo, J.
      Procedia Materials Science (2015), 9 (), 298-304CODEN: PMSREM; ISSN:2211-8128. (Elsevier B.V.)
      In the present work, two-synthesis method for copper nanoparticles (Cu NPs) in polyvinyl chloride polymer (PVC) had been developed by adding previously synthesized NPs to the resin and by an in situ synthesis of the NPs. The resin was mixed with additives to enhance obtaining a pasty mixt. called plastisol. The obtained plastisol was liq. at room temp. and had viscoelastic and pseudoplastic properties. The plastisol showed changes in its mech. properties by heat action, like a remarkable increase of viscosity at high temps., passing from the initial liq. state to solid state at curing temp. (180-200°C). Cu NPs were synthesized previously by microwave assisted polyol method, using copper acetate (CuAc2) as precursor, ascorbic acid (AA) as reducing agent, polivinilpirrolidone (PVP) as stabilizer and ethylene glycol as solvent. In this synthesis ethylene glycol (EG), a diol widely used in polyol method; was used as a solvent. Microwaves provided thermal heating, an alternative to the conventional heating by convection. The microwave irradn. was successfully used to warm dielec. materials, considering the property of tangent loss (tan δ), the higher the value, the greater transformation of electromagnetic microwave energy into heat energy was achieved, this one occurs preferably in polyol, such as ethylene, which has high dielec. const. Different concns. of plasticizer and several temps. were evaluated for curing nanocomposites (Cu NPs/PVC). To obtain films of Cu NPs/PVC, a coating technique over a substrate (paper or fabric transfer) was used. Films were prepd. in order to produce a material with further bactericidal activity. The characterization was performed by x-ray diffraction and UV visible spectrophotometry.
    49. 49
      Wu, S.; Liu, T.; Zeng, W.; He, J.; Yu, W.; Gou, Z. Rose-like Cu2O synthesized by assisted PVP K30 hydrothermal Method. J Mater Sci: Mater Electron. 2013, 24, 2404– 2409,  DOI: 10.1007/s10854-013-1109-2
      49
      Rose-like Cu2O synthesized by assisted PVP K30 hydrothermal method
      Wu, Shufang; Liu, Tianmo; Zeng, Wen; He, Jiejun; Yu, Weijie; Gou, Zhongping
      Journal of Materials Science: Materials in Electronics (2013), 24 (7), 2404-2409CODEN: JSMEEV; ISSN:0957-4522. (Springer)
      Rose-like Cu2O nanoflowers have been synthesized by polyvinylpyrrolidone K30 (PVP K30)-assisted hydrothermal method. Here, copper sulfate CuSO4 and sodium hydroxide NaOH were used as raw materials. The synthesized Cu2O powders were characterized by X-ray diffraction (XRD) and field emission SEM (FESEM). XRD pattern exhibited the nanocryst. nature with cubic structure for the synthesized nanostructures. FESEM images indicated that the rose-like Cu2O nanostructures are composed of many nearly rectangular shape nanosheets in size of about 1-2 μm in width and length and approx. 50-60 nm in thickness. Anal. results reveal that PVP K30 plays a vital role in formation of rose-like Cu2O nanoflower in this work. The probable formation mechanism of rose-like Cu2O nanoflower was discussed.
    50. 50
      Zhang, X.; Yin, H.; Cheng, X.; Hu, H.; Yu, Q.; Wang, A. Effects of various polyoxyethylene sorbitan monooils (Tweens) and sodium dodecyl sulfate on reflux synthesis of copper nanoparticles. Mater. Res. Bull. 2006, 41, 2041– 2048,  DOI: 10.1016/j.materresbull.2006.04.008
      50
      Effects of various polyoxyethylene sorbitan monooils (Tweens) and sodium dodecyl sulfate on reflux synthesis of copper nanoparticles
      Zhang, Xifeng; Yin, Hengbo; Cheng, Xiaonong; Hu, Huifeng; Yu, Qi; Wang, Aili
      Materials Research Bulletin (2006), 41 (11), 2041-2048CODEN: MRBUAC; ISSN:0025-5408. (Elsevier B.V.)
      Size-controlled synthesis of phase pure Cu nanoparticles was carried out by using copper sulfate pentahydrate as a precursor, ascorbic acid as a reductant, Tweens and sodium dodecyl sulfate (SDS) as modifiers in an aq. soln. at 80°. The as-prepd. Cu nanoparticles were characterized by powder XRD, TEM, selected area electron diffraction (SAED), and FTIR. The stabilizing effects of SDS and Tweens on the Cu nanoparticles should be through the coordination between Cu nanoparticles and the resp. sulfate group and oxygen-contg. bond. The synergic effect of the composite SDS and Tweens on Cu nanoparticles was different from those arising from the individuals.
    51. 51
      El-Nahhal, I. M.; Salem, J.; Anbar, R.; Kodeh, F. S.; Elmanama, A. Preparation and antimicrobial activity of ZnO-NPs coated cotton/starch and their functionalized ZnO-Ag/cotton and Zn(II) curcumin/cotton materials. Sci. Rep. 2020, 10, 5410  DOI: 10.1038/s41598-020-61306-6
      51
      Preparation and antimicrobial activity of ZnO-NPs coated cotton/starch and their functionalized ZnO-Ag/cotton and Zn(II) curcumin/cotton materials
      El-Nahhal, Issa M.; Salem, Jamil; Anbar, Rawan; Kodeh, Fawzi S.; Elmanama, Abdelraouf
      Scientific Reports (2020), 10 (1), 5410CODEN: SRCEC3; ISSN:2045-2322. (Nature Research)
      ZnO-NPs coated cotton or starched cotton fibers were successfully prepd. via ultrasound irradn. Different concns. of sol. corn starch (1-3 starch wt.%) were used to stabilize ZnO-NPs onto the surface of cotton fabrics as entrapped species. The use of none-toxic biocompatible starch has improved the adhesion properties of the cotton fibers towards ZnO-NPs. This also enhanced the durability of ZnO-NPs onto the cotton fabrics and decreased their leaching from the surface of cotton fabrics. When 3 starch wt.% soln. was used, deposition of ZnO-NP increased by 53% after 10 washing cycles. The antibacterial activity against Staphylococcus aureus and Escherichia coli increased by 50 and 21.5%, resp. Functionalization of ZnO coated cotton with silver nanoparticles (Ag-NPs) and curcumin results in formation of ZnO-Ag/cotton and Zn(II) curcumin/cotton composites. The functionalized nanocomposites ZnO-Ag coated cotton material showed a synergistic antimicrobial behavior than that of individual ZnO/cotton material. The Zn(II) curcumin complex coated cotton showed higher antibacterial activities against both Staphylococcus aureus (Gram-pos.) and Escherichia coli (Gram-neg.) bacteria than that of the ZnO/cotton material.
    52. 52
      El-Nahhal, I. M.; Elmanama, A. A.; El Ashgar, N. A.; Amara, N.; Selmane, M.; Chehimi, M. C. Stabilization of nano-structured ZnO particles onto the surface of cotton fibers using different surfactants and their antimicrobial activity. Ultrason. Sonochem. 2017, 38, 478– 487,  DOI: 10.1016/j.ultsonch.2017.03.050
      52
      Stabilization of nano-structured ZnO particles onto the surface of cotton fibers using different surfactants and their antimicrobial activity
      El-Nahhal, Issa M.; Manamah, Abed El Raouf; Al Ashgar, Nizam M.; Amara, Nadia; Selmane, Mohamed; Chehimi, Mohamed M.
      Ultrasonics Sonochemistry (2017), 38 (), 478-487CODEN: ULSOER; ISSN:1350-4177. (Elsevier B.V.)
      ZnO NPs were prepd. and deposited onto cotton fibers via ultrasound irradn. successfully. Different surfactants (SDS, HY, CTAB, TX-100) have been used to stabilize, homogenize the coated ZnO NPs and control their shape and size as encapsulated species. The use of surfactants has improved the durability of ZnO NPs and decreased its leaching in particular SDS. The small mean crystallite size for ZnO particles due to the use of surfactants is the main reason for decreasing the leached of ZnO particles from cotton substrate. SEM and XRD anal. revealed information about the shape and size of the coated ZnO nanoparticles. The use of SDS and HY surfactants in the synthesis of ZnO NPs coated fabrics showed the highest antibacterial and antifungal activities against different pathogenic bacterial and fungal species with high redn. reached over 90%.
    53. 53
      Román, L. E.; Gomez, E. D.; Solís, J. L.; Gómez, M. M. Antibacterial Cotton Fabric Functionalized with Copper Oxide Nanoparticles. Molecules 2020, 25, 5802  DOI: 10.3390/molecules25245802
      53
      Antibacterial cotton fabric functionalized with copper oxide nanoparticles
      Roman, Luz E.; Gomez, Enrique D.; Solis, Jose L.; Gomez, Monica M.
      Molecules (2020), 25 (24), 5802CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
      Textiles functionalized with cupric oxide (CuO) nanoparticles have become a promising option to prevent the spread of diseases due to their antimicrobial properties, which strongly depend on the structure and morphol. of the nanoparticles and the method used for the functionalization process. This article presents a review of work focused on textiles functionalized with CuO nanoparticles, which were classified into two groups, namely, in situ and ex situ. Moreover, the analyzed bacterial strains, the resistance of the antimicrobial properties of textiles to washing processes, and their cytotoxicity were identified. Finally, the possible antimicrobial mechanisms that could develop in Gram-pos. and Gram-neg. bacteria were described.
    54. 54
      Naika, H. R.; Lingaraju, K.; Manjunath, K.; Kumar, D.; Nagaraju, G.; Suresh, D.; Nagabhushana, H. Green synthesis of CuO nanoparticles using Gloriosa superba L. extract and their antibacterial activity. J. Taibah Univ. Sci. 2015, 9, 7– 12,  DOI: 10.1016/j.jtusci.2014.04.006
      There is no corresponding record for this reference.
    55. 55
      (a) Azam, A.; Ahmed, A. S.; Oves, M.; Khan, M. S.; Habib, S. S.; Memic, A. Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study. Int. J. Nanomed. 2012, 7, 6003– 6009,  DOI: 10.2147/IJN.S35347
      55a
      Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study
      Azam, Ameer; Ahmed, Arham S.; Oves, Mohammad; Khan, Mohammad S.; Habib, Sami S.; Memic, Adnan
      International Journal of Nanomedicine (2012), 7 (), 6003-6009CODEN: IJNNHQ; ISSN:1178-2013. (Dove Medical Press Ltd.)
      Background: Nanomaterials have unique properties compared to their bulk counterparts. For this reason, nanotechnol. has attracted a great deal of attention from the scientific community. Metal oxide nanomaterials like ZnO and CuO have been used industrially for several purposes, including cosmetics, paints, plastics and textiles. A common feature that these nanoparticles exhibit is their antimicrobial behavior against pathogenic bacteria. In this report, we demonstrate the antimicrobial activity of ZnO, CuO and Fe2O3 nanoparticles against Gram-pos. and Gram-neg. bacteria. Methods and Results: Nanosized particles of three metal oxides (ZnO, CuO and Fe2O3) were synthesized by a sol-gel combustion route and characterized by X-ray diffraction, Fourier-transform IR spectroscopy and transmission electron microscopy techniques. X-ray diffraction results confirmed the single-phase formation of all three nanomaterials. The particle sizes were obsd. to be 18, 22 and 28 nm for ZnO, CuO and Fe2O3, resp. We used these nanomaterials to evaluate their antibacterial activity against both Gram-neg. (Escherichia coli and Pseudomonas aeruginosa) and Gram-pos. (Staphylococcus aureus and Bacillus subtilis) bacteria. Conclusion: Among the three metal oxide nanomaterials, ZnO showed greatest antimicrobial activity against both Gram-pos. and Gram-neg. bacteria used in this study. It was obsd. that ZnO nanoparticles have excellent bactericidal potential, while Fe2O3 nanoparticles exhibited the least bactericidal activity. The order of antibacterial activity was demonstrated to be the following: ZnO > CuO > Fe2O3.
      (b) Azam, A.; Ahmed, A. S.; Oves, M.; Khan, M. S.; Habib, S. S.; Memic, A. Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study. Int. J. Nanomed. 2012, 7, 6003– 6009,  DOI: 10.2147/IJN.S35347
      55b
      Antimicrobial activity of metal oxide nanoparticles against Gram-positive and Gram-negative bacteria: a comparative study
      Azam, Ameer; Ahmed, Arham S.; Oves, Mohammad; Khan, Mohammad S.; Habib, Sami S.; Memic, Adnan
      International Journal of Nanomedicine (2012), 7 (), 6003-6009CODEN: IJNNHQ; ISSN:1178-2013. (Dove Medical Press Ltd.)
      Background: Nanomaterials have unique properties compared to their bulk counterparts. For this reason, nanotechnol. has attracted a great deal of attention from the scientific community. Metal oxide nanomaterials like ZnO and CuO have been used industrially for several purposes, including cosmetics, paints, plastics and textiles. A common feature that these nanoparticles exhibit is their antimicrobial behavior against pathogenic bacteria. In this report, we demonstrate the antimicrobial activity of ZnO, CuO and Fe2O3 nanoparticles against Gram-pos. and Gram-neg. bacteria. Methods and Results: Nanosized particles of three metal oxides (ZnO, CuO and Fe2O3) were synthesized by a sol-gel combustion route and characterized by X-ray diffraction, Fourier-transform IR spectroscopy and transmission electron microscopy techniques. X-ray diffraction results confirmed the single-phase formation of all three nanomaterials. The particle sizes were obsd. to be 18, 22 and 28 nm for ZnO, CuO and Fe2O3, resp. We used these nanomaterials to evaluate their antibacterial activity against both Gram-neg. (Escherichia coli and Pseudomonas aeruginosa) and Gram-pos. (Staphylococcus aureus and Bacillus subtilis) bacteria. Conclusion: Among the three metal oxide nanomaterials, ZnO showed greatest antimicrobial activity against both Gram-pos. and Gram-neg. bacteria used in this study. It was obsd. that ZnO nanoparticles have excellent bactericidal potential, while Fe2O3 nanoparticles exhibited the least bactericidal activity. The order of antibacterial activity was demonstrated to be the following: ZnO > CuO > Fe2O3.
    56. 56
      Abboud, Y.; Saffaj, T.; Chagraoui, A.; El Bouari, A.; Brouzi, K.; Tanane, O.; Ihssane, B. Biosynthesis, characterization and antimicrobial activity of copper oxide nanoparticles (CONPs) produced using brown alga extract (Bifurcaria bifurcata). Appl. Nanosci. 2014, 4, 571– 576,  DOI: 10.1007/s13204-013-0233-x
      56
      Biosynthesis, characterization and antimicrobial activity of copper oxide nanoparticles (CONPs) produced using brown alga extract (Bifurcaria bifurcata)
      Abboud, Y.; Saffaj, T.; Chagraoui, A.; El Bouari, A.; Brouzi, K.; Tanane, O.; Ihssane, B.
      Applied Nanoscience (2014), 4 (5), 571-576CODEN: ANPACY; ISSN:2190-5517. (Springer GmbH)
      Recently, biosynthesis of nanoparticles has attracted scientists' attention because of the necessity to develop new clean, cost-effective and efficient synthesis techniques. In particular, metal oxide nanoparticles are receiving increasing attention in a large variety of applications. However, up to now, the reports on the biopreparation and characterization of nanocryst. copper oxide are relatively few compared to some other metal oxides. In this paper, we report for the first time the use of brown alga (Bifurcaria bifurcata) in the biosynthesis of copper oxide nanoparticles of dimensions 5-45 nm. The synthesized nanomaterial is characterized by UV-visible absorption spectroscopy and Fourier transform IR spectrum anal. X-ray diffraction confirms the formation and the cryst. nature of copper oxide nanomaterial. Further, these nanoparticles were found to exhibit high antibacterial activity against two different strains of bacteria Enterobacter aerogenes (Gram neg.) and Staphylococcus aureus (Gram pos.).
    57. 57
      Speranza, G.; Gottardi, G.; Pederzolli, C.; Lunelli, L.; Canteri, R.; Pasquardini, L. Role of chemical interactions in bacterial adhesion to polymer surfaces. Biomaterials 2004, 25, 2029– 2037,  DOI: 10.1016/j.biomaterials.2003.08.061
      57
      Role of chemical interactions in bacterial adhesion to polymer surfaces
      Speranza, G.; Gottardi, G.; Pederzolli, C.; Lunelli, L.; Canteri, R.; Pasquardini, L.; Carli, E.; Lui, A.; Maniglio, D.; Brugnara, M.; Anderle, M.
      Biomaterials (2004), 25 (11), 2029-2037CODEN: BIMADU; ISSN:0142-9612. (Elsevier Science Ltd.)
      Development of biomaterial-related infections is attracting an increasing interest due to the significant percentage of implant failure in the hospital care. Recent literature puts in evidence the dependence of the infection risk on the different biomaterials used, because of the different interactions between material surface and micro-organisms. Despite this, the mechanisms underlying the adhesion of bacteria to the biomaterial surface are still unclear. Aim of this work was to study the initial events of the processes responsible for the bacterial adhesion on polymers in order to prevent the development of bacterial infections and the consequent failure and replacement of biomedical devices. Electrostatic and Lifshitz-van der Waals forces are usually considered responsible for the interactions at the biomaterial interface. A new term that involves Lewis acid-base interactions was here introduced to better describe the bacterial adhesion to the polymer surface. Two requirements are needed to test this hypothesis: the development of an ideal polymeric surface in terms of chem. and morphol. properties and the choice of a specific bacterial strain to be utilized as "probe". Expts. were worked out using an Escherichia coli (Gram-) strain that represent one of the principal isolates from infected biomaterial implants and its adhesion was investigated on polymers having different acid/basic character. The findings indicated that the bacterial adhesion is influenced by the chem. properties of the polymeric surface. These results may be interpreted taking into account a mechanism in which the acid/base (Lewis) interaction plays an important role.
    58. 58
      Guzman, M.; Dille, J.; Godet, S. Synthesis and antibacterial activity of silver nanoparticles against gram-positive and gram-negative bacteria. Nanomedicine 2012, 8, 37– 45,  DOI: 10.1016/j.nano.2011.05.007
      58
      Synthesis and antibacterial activity of silver nanoparticles against gram-positive and gram-negative bacteria
      Guzman, Maribel; Dille, Jean; Godet, Stephane
      Nanomedicine (New York, NY, United States) (2012), 8 (1), 37-45CODEN: NANOBF; ISSN:1549-9634. (Elsevier)
      Synthesis of nanosized particles with antibacterial properties is of great interest in the development of new pharmaceutical products. Silver nanoparticles (Ag NPs) are known to have inhibitory and bactericidal effects. In this article we present the synthesis of Ag NPs prepd. by chem. redn. from aq. solns. of silver nitrate, contg. a mixt. of hydrazine hydrate and sodium citrate as reductants and sodium dodecyl sulfate as a stabilizer. The results of the characterization of the Ag NPs show agglomerates of grains with a narrow size distribution (from 40 to 60 nm), whereas the radii of the individual particles are between 10 and 20 nm. Finally, the antibacterial activity was measured by the Kirby-Bauer method. The results showed reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The std. diln. micromethod, detg. the min. inhibitory concn. leading to inhibition of bacterial growth, is still under way. Preliminary results have been obtained. From the Clin. Editor: In this paper the synthesis of Ag NPs via chem. redn. from aq. solns. is discussed. Reasonable bactericidal activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus was demonstrated.
    59. 59
      (a) Rai, V. R.; Bai, A. J. Nanoparticles and Their Potential Application as Antimicrobials, Science against Microbial Pathogens: Communicating Current Research and Technological Advances. In Microbiology Series; Méndez-Vilas, A., Ed.; Formatex: Madrid, 2011; pp 197– 209.
      There is no corresponding record for this reference.
      (b) Ren, G.; Hu, D.; Cheng, E.; Vargas-Reus, M. A.; Reip, P.; Allaker, R. P. Characterisation of copper oxide nanoparticles for antimicrobial applications. Int. J. Antimicrob. Agents 2009, 33, 587– 590,  DOI: 10.1016/j.ijantimicag.2008.12.004
      59b
      Characterisation of copper oxide nanoparticles for antimicrobial applications
      Ren, Guogang; Hu, Dawei; Cheng, Eileen W. C.; Vargas-Reus, Miguel A.; Reip, Paul; Allaker, Robert P.
      International Journal of Antimicrobial Agents (2009), 33 (6), 587-590CODEN: IAAGEA; ISSN:0924-8579. (Elsevier B.V.)
      Copper oxide (CuO) nanoparticles were characterized and investigated with respect to potential antimicrobial applications. It was found that nanoscaled CuO, generated by thermal plasma technol., contains traces of pure Cu and Cu2O nanoparticles. Transmission electron microscopy (TEM) demonstrated particle sizes in the range 20-95 nm. TEM energy dispersive spectroscopy gave the ratio of copper to oxygen elements as 54.18% to 45.26%. The mean surface area was detd. as 15.69 m2/g by Brunau-Emmet-Teller (BET) anal. CuO nanoparticles in suspension showed activity against a range of bacterial pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli, with min. bactericidal concns. (MBCs) ranging from 100 μg/mL to 5000 μg/mL. The ability of CuO nanoparticles to reduce bacterial populations to zero was enhanced in the presence of sub-MBC concns. of silver nanoparticles. Studies of CuO nanoparticles incorporated into polymers suggest release of ions may be required for optimum killing.
    60. 60
      Pena, M. M. O.; Koch, K. A.; Thiele, D. J. Dynamic regulation of copper uptake and detoxification genes in Saccharomyces cerevisiae. Mol. Cell. Biol. 1998, 18, 2514– 2523,  DOI: 10.1128/MCB.18.5.2514
      60
      Dynamic regulation of copper uptake and detoxification genes in Saccharomyces cerevisiae
      Pena, Maria Marjorette O.; Koch, Keith A.; Thiele, Dennis J.
      Molecular and Cellular Biology (1998), 18 (5), 2514-2523CODEN: MCEBD4; ISSN:0270-7306. (American Society for Microbiology)
      The essential yet toxic nature of copper demands tight regulation of the copper homeostatic machinery to ensure that sufficient copper is present in the cell to drive essential biochem. processes yet prevent the accumulation to toxic levels. In Saccharomyces cerevisiae, the nutritional copper sensor Mac1p regulates the copper-dependent expression of the high affinity Cu(I) uptake genes CTR1, CTR3, and FRE1, while the toxic copper sensor Ace1p regulates the transcriptional activation of the detoxification genes CUP1, CRS5, and SOD1 in response to copper. In this study, the authors characterized the tandem regulation of the copper uptake and detoxification pathways in response to the chronic presence of elevated concns. of copper ions in the growth medium. Upon addn. of CuSO4, mRNA levels of CTR3 were rapidly reduced to eightfold the original basal level whereas the Ace1p-mediated transcriptional activation of CUP1 was rapid and potent but transient. CUP1 expression driven by an Ace1p DNA binding domain-herpes simplex virus VP16 transactivation domain fusion was also transient, demonstrating that this mode of regulation occurs via modulation of the Ace1p copper-activated DNA binding domain. In vivo di-Me sulfate footprinting anal. of the CUP1 promoter demonstrated transient occupation of the metal response elements by Ace1p which paralleled CUP1 mRNA expression. Anal. of a Mac1p mutant, refractile for copper-dependent repression of the Cu(I) transport genes, showed an aberrant pattern of CUP1 expression and copper sensitivity. These studies (i) demonstrate that the nutritional and toxic copper metalloregulatory transcription factors Mac1p and Ace1p must sense and respond to copper ions in a dynamic fashion to appropriately regulate copper ion homeostasis and (ii) establish the requirement for a wild-type Mac1p for survival in the presence of toxic copper levels.
    61. 61
      Kim, J. H.; Cho, H.; Ryu, S. E.; Choi, M. U. Effects of metals ions on the activity of protein tyrosine phosphate VHR: Highly potent and reversible oxidative inactivation by Cu2O ion. Arch. Biochem. Biophys. 2000, 382, 72– 80,  DOI: 10.1006/abbi.2000.1996
      61
      Effects of Metal Ions on the Activity of Protein Tyrosine Phosphatase VHR: Highly Potent and Reversible Oxidative Inactivation by Cu2+ Ion
      Kim, Jin-Hahn; Cho, Hyeongjin; Ryu, Seong-Eon; Choi, Myung-Un
      Archives of Biochemistry and Biophysics (2000), 382 (1), 72-80CODEN: ABBIA4; ISSN:0003-9861. (Academic Press)
      The posttranslational regulation of protein tyrosine phosphatases (PTPs) has been suggested to have a crucial role in maintaining the phosphotyrosine level in cells. Here we examd. the regulatory effects of metal ions on human dual-specificity vaccinia H1-related protein tyrosine phosphatase (VHR) in vitro. Among various metal ions examd., Fe3+, Cu2+, Zn2+, and Cd2+ exerted their inactivation effects on VHR, and Cu2+ is the most potent inactivator. The VHR activity inactivated by the metal ions except Cu2+ was significantly restored by EDTA. The efficacy of Cu2+ for the VHR inactivation was about 200-fold more potent than that of H2O2. Cu2+ also inactivated other PTPs including PTP1B and SHP-1. The Cu2+-mediated inactivation at the submicromolar range was eradicated by dithiothreitol treatment. The loss of VHR activity correlated with the decreased [14C]iodoacetate labeling of active-site cysteine, suggesting that Cu2+ brought about the oxidn. of the active-site cysteine. In contrast, Zn2+ that exerted an inactivation effect at millimolar concns. appeared not directly linked to the active-site cysteine, as indicated by the fact that [14C]iodoacetate labeling was unaffected and that the effect of Zn2+ on the Y78F mutant was increased. The redn. potential of VHR was estd. to be -331 mV by utilizing the reversibility of the redox state of VHR. Thus, we conclude that the highly potent Cu2+ inactivation of VHR is a consequence of the oxidn. of the active-site cysteine and the mode of Zn2+ inactivation is distinct from that of Cu2+. (c) 2000 Academic Press.
    62. 62
      Guzman, M.; Arcos, M.; Dille, J.; Godet, S.; Rousse, C. Effect of the Concentration of NaBH4 and N2H4 as Reductant Agent on the Synthesis of Copper Oxide Nanoparticles and its Potential Antimicrobial Applications. Nano Biomed. Eng. 2018, 10, 392– 405,  DOI: 10.5101/nbe.v10i4.p392-405
      62
      Effect of the concentration of NaBH4 and N2H4 as reductant agent on the synthesis of copper oxide nanoparticles and its potential antimicrobial applications
      Guzman, Maribel; Arcos, Mariella; Dille, Jean; Godet, Stephane; Rousse, Celine
      Nano Biomedicine and Engineering (2018), 10 (4), 392-405CODEN: NBEAA2; ISSN:2150-5578. (Nano Biomedicine and Engineering)
      The antibacterial activity of various nanoparticles is gaining increasing interest due to its potential medical applications. In this work, we presented the synthesis of copper oxide nanoparticles prepd. by chem. redn. from aq. solns. of copper sulfate (CuSO4) with sodium borohydride (NaBH4) and hydrazine hydrate (N2H4) as reductant and polyvinylpyrrolidone (PVP) as stabilizer. The X-ray diffraction spectra showed the formation of tenorite (CuO) and cuprite (Cu2O) nanoparticles when different ratios of CuSO4/NaBH4 and CuSO4/N2H4 were used. Photographs obtained by transmission electron microscopy (TEM) showed agglomerates of grains with a narrow size distribution (from 20 to 70 nm), whereas the radii of the individual particles were between 2 and 20 nm. Smaller nanoparticles and narrower particle size distributions were obtained when NaBH4 was used. The results of antibacterial activity using the Kirby-Bauer method showed that nanoparticles obtained with NaBH4 presented a reasonable bactericidal activity. Pseudomonas aureginosa and Staphylococcus aureus were more susceptible to the particle size than Escherichia coli. In addn., with small amts. of Cu2O in samples of CuO nanoparticles, the antibacterial susceptibility against Pseudomonas aureginosa was improved. Finally, nanoparticles of CuO incorporated into cotton by applying ultrasound waves remained impregnated after five washes.
    63. 63
      Badawy, S.-M.; El-Khashab, R.-A.; Nayl, A.-A. Synthesis, Characterization and Catalytic Activity of Cu/Cu2O Nanoparticles Prepared in Aqueous Medium. Bull. Chem. React. Eng. Catal. 2015, 10, 169– 174,  DOI: 10.9767/bcrec.10.2.7984.169-174
      63
      Synthesis, characterization and catalytic activity of Cu/Cu2O nanoparticles prepared in aqueous medium
      Badawy, Sayed M.; El-Khashab, R. A.; Nayl, A. A.
      Bulletin of Chemical Reaction Engineering and Catalysis (2015), 10 (2), 169-174CODEN: BCRECO; ISSN:1978-2993. (Diponegoro University, Dep. of Chemical Engineering)
      Copper/Copper oxide (Cu/Cu2O) nanoparticles were synthesized by modified chem. redn. method in an aq. medium using hydrazine as reducing agent and copper sulfate pentahydrate as precursor. The Cu/Cu2O nanoparticles were characterized by X-ray Diffraction (XRD), Energy Disper-sive X-ray Fluorescence (EDXRF), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The anal. revealed the pattern of face-centered cubic (fcc) crystal structure of copper Cu metal and cubic cuprites structure for Cu2O. The SEM result showed monodispersed and ag-glomerated particles with two micron sizes of about 180 nm and 800 nm, resp. The TEM result showed few single crystal particles of face-centered cubic structures with av. particle size about 11-14 nm. The catalytic activity of Cu/Cu2O nanoparticles for the decompn. of hydrogen peroxide was investigated and compared with manganese oxide MnO2. The results showed that the second-order equation provides the best correlation for the catalytic decompn. of H2O2 on Cu/Cu2O. The catalytic activity of hydrogen peroxide by Cu/Cu2O is less than the catalytic activity of MnO2 due to the presence of copper metal Cu with cuprous oxide Cu2O. 2015 BCREC UNDIP. All rights reserved.
    64. 64
      (a) Perelshtein, I.; Perkas, N.; Gedanken, A. Ultrasonic Coating of Textiles by Antibacterial and Antibiofilm Nanoparticles. In Handbook of Ultrasonics and Sonochemistry; Ashokkumar, M. Ed.; Springer: Singapore, 2015; pp 1– 27.
      There is no corresponding record for this reference.
      (b) Abramova, A. V.; Abramov, V. O.; Gedanken, A.; Perelshtein, I.; Bayazitov, V. M. An ultrasonic technology for production of antibacterial nanomaterials and their coating on textiles. Beilstein J Nanotechnol. 2014, 5, 532– 536,  DOI: 10.3762/bjnano.5.62
      64b
      An ultrasonic technology for production of antibacterial nanomaterials and their coating on textiles
      Abramova, Anna V.; Abramov, Vladimir O.; Gedanken, Aharon; Perelshtein, Ilana; Bayazitov, Vadim M.
      Beilstein Journal of Nanotechnology (2014), 5 (), 532-536, 5 pp.CODEN: BJNEAH; ISSN:2190-4286. (Beilstein-Institut zur Foerderung der Chemischen Wissenschaften)
      A method for the prodn. of antibacterial ZnO nanoparticles has been developed. The technique combines passing an elec. current with simultaneous application of ultrasonic waves. By using high-power ultrasound a cavitation zone is created between two zinc electrodes. This leads to the possibility to create a spatial elec. discharge in water. Creation of such discharge leads to the depletion of the electrodes and the formation of ZnO nanoparticles, which demonstrate antibacterial properties. At the end of this reaction the suspension of ZnO nanoparticles is transported to a specially developed ultrasonic reactor, in which the nanoparticles are deposited on the textile. The nanoparticles are embedded into the fibers by the cavitation jets, which are formed by asym. collapsing bubbles in the presence of a solid surface and are directed towards the surface of textile at very high velocities. Fabrics coated with ZnO nanoparticles by using the developed method showed good antibacterial activity against E. coli.
      (c) Ma, J.; Chen, S.; Liu, C.; Xu, W.; Wang, S. The influences of ultrasonic on embedding nanoparticles into porous fabric materials. Appl. Acoust. 2008, 69, 763– 769,  DOI: 10.1016/j.apacoust.2007.05.012
      There is no corresponding record for this reference.
    65. 65
      Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk and Dilution Susceptibility Test: M2-A9. Performance Standards for Antimicrobial Susceptibility Testing. 18th Informational Supplement: M100-S18 , 2008.
      There is no corresponding record for this reference.