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Biogenic Photo-Catalyst TiO2 Nanoparticles for Remediation of Environment Pollutants
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  • Boya Palajonnala Narasaiah
    Boya Palajonnala Narasaiah
    CASEST, School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
    Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima 15081, Peru
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  • Pravallika Banoth
    Pravallika Banoth
    School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
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  • Angel Guillermo Bustamante Dominguez
    Angel Guillermo Bustamante Dominguez
    Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima 15081, Peru
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  • Badal Kumar Mandal*
    Badal Kumar Mandal
    Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India
    *Email: [email protected]
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  • Challa Kiran Kumar
    Challa Kiran Kumar
    Technology Mission Division, Department of Science and Technology, Ministry of Science and Technology, MoS&T, New Delhi 110030, India
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  • Crispin H. W. Barnes
    Crispin H. W. Barnes
    Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE 2, U.K.
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  • Luis De Los Santos Valladares*
    Luis De Los Santos Valladares
    Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE 2, U.K.
    School of Materials Science and Engineering, Northeastern University, No 11, Lane 3, Wenhua Road, Heping District, Shenyang, Liaoning 110819, People’s Republic of China
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0001-5930-9916
  • Pratap Kollu*
    Pratap Kollu
    CASEST, School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
    *Email: [email protected]
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    Orcidhttps://orcid.org/0000-0001-6250-9396
Open PDFSupporting Information (1)

ACS Omega

Cite this: ACS Omega 2022, 7, 30, 26174–26189
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https://doi.org/10.1021/acsomega.2c01763
Published July 20, 2022

Copyright © 2022 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Abstract

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This article reports a benign environmentally friendly fabrication method of titanium dioxide (TDO) nanoparticles (named TDO NPs3, TDO NPs5, and TDO NPs8) using aqueous extract of durva herb waste. This synthesis process avoids use of harmful substances and persistent chemicals throughout the order and enables us to control the size of the nanomaterials. Characterization of TDO nanoparticles was analyzed by ultraviolet–visible spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The morphological nature of the TDO samples was inspected by transmission electron microscopy, which indicated that the TDO NPs3, TDO NPs5, and TDO NPs8 were spherical in shape, with average sizes of 5.14, 12.54, and 29.61 nm, respectively. The stability of TDO nanoparticles was assessed using thermogravimetric analysis and dynamic light scattering analysis. These samples could be used for degradation of polluting industrial textile dyes, such as methylene blue (MB) and rhodamine B (Rh-B). Remarkably, the TDO NPs3 sample (5.14 nm size) exhibits a noticeable degradation of the MB dye in a shorter time period (50 min) than the TDO NPs8 sample with a size of 29.61 nm (120 min). The TDO NPs3 sample was also tested for degradation of Rh-B dye, showing high degradation efficiency over a short period of time (60 min). In contrast, the TDO NPs8 sample showed degradation of the Rh-B dye in 120 min. The effect of the dye concentration and the catalyst dose to remove dye pollutants has also been investigated. The synthesized TDO NPs act as exceptional catalysts for the degradation of dyes, and they are promising materials for the degradation of industrial polluting dyes.

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This paper was published ASAP on July 20, 2022, with text missing from the Supporting Information file. The corrected version was reposted on August 2, 2022.

1. Introduction

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Nanotechnology involves manipulating matter at the nanoscale. (1) Due to an increased surface to volume ratio, extreme physical and chemical changes occur in materials at this level. In recent years, nanotechnology has rapidly gained popularity with its applications in science and technology for creating new materials at the nanoscale level that are beneficial to various areas such as the economy and the environment. (2) Recent studies have featured potential applications of TiO2 nanoparticles (NPs) in various fields such as pigments, photo-catalysis, solar energy conversion, sensor technology, and biological activity such as antibacterial activities, anticancer activity, and antifungal activities. (3,4) In spite of their wide range of applications, TiO2 NPs are characterized by a number of miscellaneous properties, such as high chemical stability, high redox potential, low cost, and eco-friendly nature. (5,6) In addition, these properties are also heavily affected by the method by which NPs are synthesized, such as the specific surface area, crystal structure, particles shape, and crystallite size. (7) TiO2 NPs have three distinct polymorph crystalline forms, that is, the tetragonal structure (rutile), orthorhombic structure (brookite), and tetragonal structure (anatase). Rutile is the stable phase and can be synthesized by heating at high temperatures from anatase and brookite. (8) Each crystalline phase exhibits different physical properties depending on its structure and particle size, making it suitable for a range of applications. For example, a band gap of 3.2 eV indicates that the anatase phase can be activated under exposure to ultraviolet light, and thus, it is often used in photo-catalysis. (9)
There is an increasing demand for biological methods, which use plant components and microbes, for the synthesis of nanoscale materials since they avoid high pressure and temperature which takes more time and is not friendly to the environment. (10) These can be overcome by developing an eco-friendly method to synthesize nanomaterials. In this way, some attempts have been reported such as Ag/TiO2 nanocomposites synthesized from Euphorbia heterophylla leaf extract (11) and TiO2 NPs produced from Trigonella foenum-graecum extract (12) and from micro-organism Caenorhabditis elegans Bristol strain. (13)
As coloring agents, about 10,000 commercially available dyes are used in industries including textiles, plastics, rubber, leather, cosmetics, etc., producing enormous quantities of colored wastewater. About 2% dye effluent, especially those from the textile sector, is derived from the production of over 7 × 107 dyestuffs every year. (14) Dye wastewater discharges into natural streams and rivers, causing severe environmental and aesthetic damage. This results in a serious threat to water quality and human health. (15) The direct discharge of textile effluents containing dye concentrations higher than 1 mg/L can cause serious problems for the ecosystem due to the contamination of water and soil. Besides, most dyes contain synthetic organic compounds and complex organic structures, making them non-biodegradable, carcinogenic, and irritants to the skin. (16)
Nowadays, photocatalytic pollutant dye degradation is drawing more and more attention in the field of photodegradation methods. Thus, remediation methods using mineral acids and H2O are needed for a cheaper, non-toxic alternative. (17) In this way, several methods are being used to degrade dyes, including Fenton oxidation, (18) reverse osmosis, (19) or photodegradation by using nanomaterials. (20) Among all these methods, photodegradation with a multi-lamp photoreactor technique is a simple method, that is, a closed instrument setup, an easy handling process, and the reaction can be carried out at room temperature.
Therefore, the objective of the present study was to synthesize for the first time, environmentally benign TDO NP samples using agro-waste durva grass extract in the absence of chemical reducing agents, toxic solvents, or stabilizing agents. The synthesized TDO NP samples were characterized by several advanced analytical techniques such as X-ray diffraction (XRD), UV–vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and BET analysis. The synthesized TDO NP sample exhibited outstanding photodegradation efficiency for the photodegradation of environmental polluting dyes such as rhodamine B (Rh-B) and methylene blue (MB) under ultraviolet light exposure.

2. Experimental Section

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2.1. Materials and Methods

The chemicals of analytical grade (A.R) were purchased from Sigma-Aldrich, India, and prepared as needed. The chemicals used were titanium tetraisopropoxide (TIP) (purity 97%), Rh-B (purity 99%), MB (purity 99%), and double-distilled water (DDW), which is used as a reaction medium.

2.2. Preparation of Durva Grass Aqueous Extract

Approximately 3 g of dried durva grass powder was dispersed in 100 mL of double-distilled water and incubated for 2 h at 70 °C until a deep-green solution was formed. The grass was collated from sunflower agriculture land near the Tungabhadra River, Andhra Pradesh, India. Using a Whatman filter paper centrifugation at 5000 rpm, the aqueous extract was filtered, and the supernatant liquid was stored at 4 °C for use in synthesizing TDO NPs.

2.3. Synthesis of TiO2 NPs by Using Durva Grass Aqueous Extract

The TIP precursor of 0.05 M was dissolved in 30 mL of double-distilled water, and then, 30 mL of durva grass aqueous extracts of 1:1 (v/v) each was added at a rate of 1:1 (v/v) with vigorous stirring for 3 h at 80 °C until a brownish-yellow-colored precipitation was observed. After centrifuging for 30 min, the solution was collected and washed with double-distilled water to remove any residual contaminants. The precipitate was dried in an oven and ground to get a fine powder using a mortar–pestle and then annealed at three different temperatures 300, 500, and 800 °C for 3 h, and the obtained samples were labeled TDO NPs3, TDO NPs5, and TDO NPs8 samples, respectively. The dried powder samples were processed and stored for subsequent photocatalytic degradation of Rh-B and MB after being annealed.

2.4. Characterization of the Synthesized TDO NPs

UV–visible spectroscopy was used to characterize the synthesized TDO NPs (Jasco V-670 UV–visible double-beam spectrophotometer). The wavelength range of 200–800 nm was used for recording the absorption spectra. Based on the Fourier transform infrared (FT-IR) study, the functional group was predicted in the surface agro-waste durva grass extract and TDO NPs. For this purpose, KBr pellets were used as controls, and the dried TDO NPs were analyzed in a Shimadzu’s IR AFFINITY-1 system (JASCO’s FT-IR 4100 in the diffuse reflectance mode) at a resolution of 4 cm.
Furthermore, X-ray analysis was performed on a Bruker D8 Advance diffractometer under Cu Kα radiation (λ = 1.54°) at a scanning rate of 4°/min and a step size of 0.02°. The diffractogram was recorded from 10 to 90°. The transmission electron microscopy (TEM) analysis was carried out using a JEOL-JEM 2100 transmission electron microscope at 200 kV to determine the size and shape of NPs. Selected-area electron diffraction (SAED) patterns and crystalline plane fringe spacing were obtained by using an HR-TEM system. Moreover, the polydispersity indexes (PDIs) were measured on a Horiba scientific NP analyzer (SZ-100), and a DLS study was conducted to measure the zeta potential value of TDO NP dispersion. A scattering angle of 173° was used with the sample being interpreted at 20 °C. In addition, a suspension of the sample was measured in cell culture medium at 20 °C and 150 V. A thermogravimetric analyzer (model JSM 6390 LV, JOEL 2100F, USA) with an acceleration voltage of 100 kV was used to measure the thermal stability of the TDO NPs.

2.5. Photocatalytic Activity of TDO NPs

In an aqueous solution, the photocatalytic activity of the synthesized TDO NPs was tested for degradation of model pollutant MB and Rh-B dyes. The photodegradation was performed in a low-pressure Heber multilamp photoreactor with a UV lamp (125 W, λmax 254 nm). In the absence of the photocatalyst, 60 mL of dye solution (10 mg/L) was placed in a 100 mL quartz tube and constantly agitated in dark (no light). UV–visible spectroscopy was used to track the dye solution’s color intensity change. The same experiment was then repeated in the photoreactor with various dosages of photocatalyst TDO NPs (10, 20, and 30 mg) in dark and under UV illumination. By measuring absorbance at regular time intervals between 200 and 800 nm, the photocatalytic degradation of the organic dyes MB and Rh-B was detected. Furthermore, the effect of dye doses (5 and 15 mg/L) on photodegradation of MB and Rh-B dyes was studied under the same conditions with a constant TDO NP photocatalyst dose. UV–visible spectroscopy was used to monitor photodegradation by measuring the dye solution’s absorbance.

3. Results and Discussion

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Crystalline titanium dioxide nanoparticles (TDO NP) samples (TDO NPs3, TDO NPs5, and TDO NPs8) were synthesized using durva grass aqueous extract, and this acted as both reducing and size controlling agents, preventing particle agglomeration and nucleation of NPs, that is, regulated growth of NPs. As a result, we obtained TDO NP samples for studying the photocatalytic activity of dye degradation.

3.1. UV–Visible Analysis

Figure 1 displays the UV–visible absorption spectrum of TDO NP samples. The TDO NPs3 sample had an absorption band at a maximum wavelength of 326.42 nm, which is represented in Figure 1A. TDO NPs5 had an absorption band at 328.68 nm, which is demonstrated in Figure 1B, and TDO NPs8 had an absorption band at 331.52 nm, which is noted in Figure 1C. The TDO NPs annealed at 300 °C show maximum absorption peaks in the UV range while those annealed at high temperatures between 500 and 800 °C exhibit absorption peaks in the visible range.

Figure 1

Figure 1. UV–visible absorption spectra of TDO NPs after annealing (A) sample at 300 °C, (B) sample at 500 °C, and (C) sample at 800 °C and (D) band gap energy of TDO NPs from 300 to 800 °C.

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Therefore, from the results obtained, we concluded that the absorption properties of the TDO NPs strongly depend on their size; that is, the sample annealed at 800 °C possessing the larger-size particle distribution exhibited the absorption band in the visible range. The absorption coefficient of TDO NPs is obtained using eq 1.
(1)
where α is the absorption coefficient, hν is the photon energy, and Eg is the optical band gap energy. The band gap energy (Eg) of the TDO NP samples annealed at 300–800 °C is shown in Figure 1D. By using the Tauc plot, we have calculated the band gap energy by plotting (αhν)1/2 on the y axis and the photon energy (hν) on the x axis. The optical band gap energy of the TDO NPs annealed at 300, 500, and 800 °C are 3.02, 3.18, and 3.23 eV, respectively. Therefore, on increasing the temperature from 300 to 800 °C, the band gap energy of the TDO NPs tremendously changes, and this change might be attributed to the crystal defects in the materials. The current results are strongly analogous to reported results. (21) Earlier studies on TiO2 NP-mediated aloe vera plant extracts estimated band gap energy to be 3.62 eV. (22)

3.2. Powder XRD Analysis

XRD patterns were used to determine the structural properties of the TDO NPs to identify the phase formation and crystalline nature of the nanomaterials. Figure 2A shows the powder XRD pattern of the TDO NPs3 sample representing the characteristic diffraction peaks (hkl values) of the lattice planes (Miller indices) values, which are 25.56 (101), 38.42 (004), 48.41 (020), 55.03 (121), 62.94 (204), 70.37 (116), and 82.86 (303). Therefore, the diffraction pattern of the synthesized TDO NPs3 sample reveals a tetragonal structure, matching with that of standard Match3 software (JCPDS card no.: 96-500-0224). Figure 2B displays the XRD pattern of sample TDO NPs5 that shows 2θ reflection values and characteristic diffraction hkl values of lattice planes to be 25.79 (101), 38.52 (004), 48.44 (020), 55.22 (121), 62.96 (204), 70.42 (116), 75.71 (215), and 82.97 (303). Therefore, the TDO NPs5 sample diffraction pattern confirmed the tetragonal structure and which matches with that of standard Match3 software (JCPDS card no.: 96-500-0224). Figure 2C describes the XRD pattern of the TDO NPs8 sample that shows the 2θ reflection values and characteristic diffraction hkl values of lattice planes (Miller indices) to be 25.64 (101), 37.27 (013), 38.24 (004), 39.04 (112), 48.42 (020), 54.06 (015), 55.52 (121), 63.16 (204), 69.24 (116), 70.72 (220), 75.39 (215), and 83.05 (303). Therefore, the fabricated TDO NPs8 sample has a tetragonal structure, which matches with that of standard Match3 software (JCPDS card no.: 96-900-8214). However, there are no impurity peaks in XRD pattern, so we concluded that the synthesized TDO NPs8 sample was pure and crystalline in nature. However, the XRD pattern of TDO NPs synthesized without annealing suggests no crystalline phase formation, which is shown in Figure 2D. Therefore, on increasing annealing temperature from 300 to 800 °C, the crystalline nature of TDO NPs increases due to systematic arrangement of atoms in the crystal system. Figure 2E represents the XRD pattern of standard commercial P25 nanomaterial that shows 2θ reflection values and characteristic diffraction hkl values of lattice planes to be 25.42 (101), 37.07 (013), 37.93 (004), 38.65 (112), 48.02 (020), 53.99 (015), 55.22 (121), 62.72 (204), 68.89 (116), 70.25 (220), 75.23 (215), and 82.85 (303).

Figure 2

Figure 2. XRD pattern of TDO NPs annealed at 300 °C (A), 500 °C (B), and 800 °C (C), without annealing (D), and commercial P25 NPs (E).

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The average crystallite size was calculated using Scherrer’s eq 2
(2)
where λ is the wavelength of X-ray radiation (1.5406 Å), β is full-width at half-maximum (fwhm) of reflection planes, and θ is Bragg’s angle. By using the above equation, we have calculated the average crystallite size and inter-planar distance (d) of the sample TDO NPs (Table 1). Consequently, all the samples crystallized with a tetragonal structure after annealing them from 300 to 800 °C. The average crystallite sizes obtained for these samples TDO NPs3, TDO NPs5, and TDO NPs8 are 5.88, 7.83, and 25.96 nm, respectively (Table 1). The average crystallite size of the commercial P25 nanomaterial was calculated from Scherrer’s formula, and it was around 64.84 nm. Aravind et al. (2021) synthesized TiO2 NPs with the average crystallite size of 31–42 nm using jasmine flower aqueous extract. (23)
Table 1. Structure and Geometric Parameters of TDO NPs by XRD Analysis
tem. (°C)2θfwhm valueplaned-spacing (Å)cos(θ)crystalline size (nm)
30025.691.29(101)3.480.974976.60
 38.321.68(004)2.340.944605.22
 48.411.17(200)1.870.912087.77
 55.372.38(211)1.670.885513.94
average size     5.88
50025.660.99(101)3.850.975038.60
 38.291.42(004)2.610.944696.18
 48.311.09(200)2.080.912448.35
 55.381.14(211)1.830.885478.22
average size     7.83
80025.600.30(101)3.940.9751428.38
 37.990.33(004)2.650.9455426.60
 48.360.35(200)2.080.9122626.00
 54.160.37(105)1.870.8903725.20
 55.410.38(211)1.820.8853524.66
average size     25.96

3.3. FT-IR Analysis

The functional groups in durva grass extract and their biomolecule capping on the surfaces of TDO NPs were determined using FT-IR analysis. The FT-IR spectrum of agro-waste durva grass extract in the 500–4000 cm–1 range is shown in Figure 3A. As a result, the absorption characteristic peak at 3316.43 cm–1 is associated with the hydroxyl group (−OH) stretching vibration, indicating the presence of polyphenols. Aromatic −C–H stretching vibration could be assigned to the band at around 2922.92 cm–1. Carbonyl (−C═O) stretching vibration is responsible for the peak at 1732.08 cm–1. The peak at 1382.46 cm–1 could be attributed to the carbon and nitrogen (−C–N) stretching vibration of amide.

Figure 3

Figure 3. FT-IR spectra of (A) durva grass extract (B) TDO NPs3 annealed at 300 °C, (C) TDO NPs5 annealed at 500 °C, and (D) TDO NPs8 annealed at 800 °C.

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According to the spectrum, the absorption band at 1104.42 cm–1 corresponds to the stretching vibration of carbon, oxygen, and carbon (−C–O–C−). The flexural vibration of aliphatic carbon and hydrogen is responsible for the peak at 720.44 cm–1 (−C–H). Al-hamoud et al. (2022) reported phytomolecule functional groups present (3425, 2917, 2849, 1630, 1070, and 625 cm–1, respectively) in the Pulicaria undulata plant extract. (24) The FT-IR spectrum of TDO NPs3 at 300 °C is shown in Figure 3B, with the absorption band at 3321.25 cm–1 corresponding to the stretching vibration of the −OH group, the peak at 1639.13 cm–1 corresponding to the stretching vibration of alkene (−C═C−), and the band at 423.25 cm–1 corresponding to the stretching vibration of titanium metal and oxygen (Ti–O) bonds.
Our current findings are consistent with those of FT-IR bands (34246, 3430, 1642, 1529, 1450, 1134, 1168, 1092, and 469 cm–1) of TiO2-supported biochar reported by Abodif et al. (2020). (25) The FT-IR spectrum of TDO NPs5 at 500 °C is shown in Figure 3C, with the band at 3383.56 cm–1 being attributed to the stretching vibration of the −OH group, indicating that the NPs are covered with polyphenols. The stretching vibration of titanium metal and oxygen could be assigned to the band at 432.97 cm–1 (Ti–O bond). The FT-IR spectrum of TDO NPs8 at 800 °C is depicted in Figure 3D; however, the band at 445.83 cm–1 can also be attributed to the stretching vibration of titanium metal and oxygen (Ti–O) bond. According to the findings, as the annealing temperature increased from 300 to 800 °C, the stretching vibration of titanium metal and oxygen bond (Ti–O), the band, and the atomic diffusion increased, resulting in an increase in nanomaterials’ size.

3.4. TEM Analysis

The TEM results investigate the size, crystalline/amorphous nature, inter-planar distances, and elemental composition of nanomaterials. Figure 4 shows the HR-TEM, SAED pattern, the particle size distribution, and the EDX spectrum of TiO2 NPs calcined at 300 °C. The size of TDO NPs3 is in the range of 3-6 nm with a mean diameter of 5.14 nm, and the particle magnification size distribution is shown in Figure 4A–C, and the distance between the brush spacing, that is, d-spacing, is 0.367 nm, which characterizes the reflection plane (101) (Figure 4C). The diffuse rings in the SAED pattern of the TDO NPs3 are shown in Figure 4E, where all the bright circular rings are arranged in the SAED pattern, suggesting amorphous nature of the TDO NPs3 sample. The elemental composition of the TDO NPs3 sample is examined from the EDX spectrum.

Figure 4

Figure 4. HR-TEM images of the TDO NPs3 sample annealed at 300 °C: (A) 10 nm magnification (B) 50 nm magnification, and (C) 100 nm magnification, (D) interplanar distance d values of the lattice, and (E) SAED pattern of TDO NPs and (F) existing elements in the synthesized TDO NPs.

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Figure 5A–F shows a representative image of HRTEM of TiO2 NPs at 500 °C with spherical particles having a mean diameter of 12.54 nm. Our results support the findings of Pushpamalini et al. (2021), where they reported that the average particle size of TiO2 NPs is 6.7–8.3 nm. (26)Figure 5A–C shows the particle size distribution under various magnifications of the TDO NPs5 sample with the size in the range of 8-16 nm coinciding with the XRD results according to the grid spacing plane (101). Figure 5E shows the SAED pattern of the TDO NPs5 sample; however, all bright spots in the form of concentric circular rings correspond to the polycrystalline nature of the TDO NPs5 sample. Figure 5F represents the elemental composition of the TDO NPs5 sample analyzed by EDX analysis. Therefore, the EDX spectrum shows the wt and at. % of the elements present in the sample of TDO NPs5, 62.20 wt % and 37.57 at. % of “Ti” and 22.91 wt % and 47.80 at. % of “O” atoms, and therefore, the previous results conclude that the nanomaterials obtained are pure and polycrystalline.

Figure 5

Figure 5. HR-TEM images of the TDO NPs5 sample annealed at 500 °C under (A) 20 nm magnification, (B) 50 nm magnification, and (C) 100 nm magnification, (D) interplanar distance d value of the lattice, (E) SAED pattern of TDO NPs, and (F) existing elements in the synthesized TDO NPs.

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Figure 6A–F demonstrates the HR-TEM image, particle size distribution, SAED pattern, and EDX analysis of TiO2 NPs being annealing at 800 °C. Figure 6B shows that the particle size distribution of the TDO NPs8 sample in the range of 22–34 nm with a mean diameter is 29.61 nm. Figure 6C shows that the inter-planar distance, that is, fringe “d” spacing, is 0.391 nm, which strongly matches with XRD results, corresponding to the lattice spacing (101) plane. Figure 6E shows the bright spots on the circular rings in the SAED pattern, attributed to the poly-crystalline nature of the TDO NPs8 sample. Figure 6F shows the elemental composition of the sample TDO NPs8, which is obtained from EDX analysis. Therefore, elemental composition of Ti and O in wt and at. % is 63.21 and 43.84% and 22.86 and 48.23%, respectively, which endorses the purity of the NPs with polycrystalline nature of the TDO NPs8 sample.

Figure 6

Figure 6. HR-TEM images of the TDO NPs8 sample annealed at 800 °C (A) under (B) 100 nm magnification (C) and 200 nm magnification, (D) interplanar distance d value of the lattice, (E) SAED pattern of TDO NPs, and (F) existing elements in the synthesized TDO NPs.

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3.5. DLS Analysis

Zeta potential is a key indicator for the stability of the colloidal dispersion of nanomaterials. Therefore, stability of TDO NPs was determined by the DLS method that is based on the interaction between adjacent particles or particles with similar size or mobility in colloidal dispersion of TDO NPs. From DLS analysis, the zeta potential of the TDO NPs3 sample is −41.5 mV (Figure 7A). The zeta potential of the TDO NPs5 sample is −38.4 mV (Figure 7B) and zeta potential of sample TDO NPs8 is −33.7 mV (Figure 7C). Therefore, from the results, it is clear that the higher negative values indicate very good stability of nanomaterials. (27) From the results, we conclude that the increase in temperature from 300 to 800 °C decreases zeta potential values; hence, the stability of NPs decreases due to the smaller size (5 nm) of the NPs that show higher stability. In addition, smaller-size NPs show higher mobility compared to larger NPs. Also, the stability of the TDO NPs3 sample is the highest because it was annealed at 300 °C, but in the case of the sample being annealed at 800 °C, the sedimentation tendency of its dispersion is high, leading to lower stability compared to that of the TDO NPs3 sample.

Figure 7

Figure 7. DLS spectrum of the TDO NP sample annealed at 300 °C (A), annealed at 500 °C (B), and annealed at 800 °C (C) and TGA spectrum of TDO NPs after annealing at 300 °C (D), annealing at 500 °C (E), and annealing at 800 °C (F).

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3.6. Thermal Stability Analysis of TDO NPs

Thermal stability of the fabricated TDO NPs3, TDO NPs5, and TDO NPs8 samples was studied by TGA. Figure 7D shows the TGA plot of the TDO NPs3 sample, which was annealed at 300 °C. It exhibits an initial weight loss of 8.83% due to removal of the adsorbed moisture during heating between 30 and 200 °C, and a further weight loss of 3.521% was observed after heating up to 800 °C, which may be attributed to the removal of volatile compounds. Figure 7E shows the TGA plot of the TDO NPs5 sample, which was annealed at 500 °C. It exhibits an initial weight loss of 3.549% due to removal of the adsorbed moisture during heating between 30 and 400 °C, and further weight loss of 0.4809% was observed from 400 to 800 °C, which may be attributed to the removal of volatile compounds in the sample. Figure 7F shows the TGA plot of the TDO NPs8 sample, which was annealed at 800 °C. It exhibits an initial weight loss of 1.974% due to removal of the adsorbed moisture during heating between 30 and 450 °C, and further weight loss of 0.6537% was observed from 450 to 800 °C, which is attributed to the removal of volatile compounds. From these results, we conclude that among the three samples, the synthesized TDO NPs8 sample obtained after annealing at 800 °C shows very less weight loss, suggesting that this sample is pure and has a better crystallization. This is quite similar to the results obtained by Gautam et al. (2016), who reported a weight loss of 38% after heating their synthesized TiO2 NP sample. (28) Therefore, the synthesized TDO NPs8 sample has high thermal stability.

3.7. Photoluminescence Analysis of TDO NPs

The photoluminescence (PL) studies of TDO NPs3, TDO NPs5, TDO NPs8, and standard P25 NP samples were carried out with photon-induced charge carriers in TDO NPs as shown in Figure 8. Figure 8 shows the PL spectrum of TDO NPs3, TDO NPs5, TDO NPs8 and commercial P25 nanomaterial samples. Spectra of all TDO NP samples and standard P25 nanomaterial sample were recorded at room temperature with excitation wavelength (326, 328, 331, and 328 nm), respectively. The emission photoluminescence spectrum (350–600 nm) was obtained at particular wavelengths (326, 328, 331, and 328 nm) and possessed maximum-emission bands. Figure 8A represents the emission bands of sample TDO NPs3 at 413 nm (3.00 eV) and 434 nm (2.85 eV). Figure 8B shows the PL spectrum sample TDO NPs5, which exhibits emission bands at 414 nm (2.99 eV) and 435 nm (2.85 eV). Figure 8C displays the PL spectrum sample of TDO NPs8, which exhibits emission bands at 415 nm (2.98 eV) and 436 nm (2.84). Figure 8D represents the standard P25 NP sample PL spectrum, which reveals the emission bands at 417 nm (2.97 eV) and 463 nm (2.67 eV). From the results, the emission energies of the TDO NPs are revealed to be either within the band gap or above the band gap energy (Eg) of TDO NP samples that is TDO NPs3 (3.02 eV), TDO NPs5 (3.18 eV), and TDO NPs8 (3.23 eV). The emission energies of TDO NPs higher than the band gap of TDO NPs3, TDO NPs5, and TDO NPs8 samples are attributed to the recombination of electrons in the Ti4+ conduction band with holes in O2– in the valence band. However, lower emission energies of TDO NPs than the actual band gap of TDO NPs may be due to the crystal defects or oxygen vacancies or energy levels of Ti (titanium) interstitials within the crystal system. From the results, we concluded that most of the emission energies of the TDO NPs are within the band gap of the samples.

Figure 8

Figure 8. Photoluminescence spectra of TDO NPs3 (A), TDO NPs5 (B), TDO NPs8 samples (C) and commercial P25 NPs (D).

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4. Photocatalytic Activity of the Synthesized TDO NPs

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TDO nanomaterials are used extensively in the photodegradation of industrial pollutant dyes. (29) In the present work, MB and Rh-B dyes are chosen for the photodegradation of industrial pollutant dyes under UV irradiation at room temperature.

4.1. PhotoDegradation of MB Dye

The photocatalytic activity of the synthesized TDO NPs was investigated toward degradation of MB dye under UV light irradiation (λmax = 254 nm) inside a Heber multi-photoreactor. Figure 9 presents the UV–visible absorbance spectra recorded from 200 to 800 nm for MB dye under UV irradiation, and after that, sample was collected at regular time intervals. A strong absorption band at 664 nm represents the maximum wavelength of MB dye, which clearly shows a decreasing trend in intensity with time in the presence of TDO NPs3 as a photocatalyst. Diallo et al. (2016) also reported degradation of MB, Congo red, and eosin dye with UV irradiation using TiO2 NPs, which supports our present results. (30) In the present study, MB dye degraded insignificantly (6.49%) without catalysts under identical conditions within 50 min, whereas in the presence of TDO NPs3 photocatalyst, 99.35% degradation was observed under similar conditions. The degradation kinetics was checked as follows eq 3.
(3)
where C0 is the initial concentration of the dye and Ct is the concentration of dye at time “t” after UV irradiation. The obtained result shows 99.35% MB dye degradation within 50 min under UV irradiation Figure 9A shows the percentage of MB dye degradation with the catalyst (TDO NPs3). In the case of TDO NPs5, 98.05% MB degradation within 70 min was observed, which is represented in Figure 9B. However, in the case of the TDO NPs8 sample, 97.42% MB dye degradation occurred within 100 min, which is shown in Figure 9C.

Figure 9

Figure 9. UV–vis absorption spectra of MB dye degradation (A) in the presence of TDO NPs3, (B) in the presence of TDO NPs5, and (C) in the presence of TDO NPs8 under UV irradiation and percentage of MB dye degradation with catalysts and without catalysts in the (D) presence of TDO NPs3, (E) presence of TDO NPs5, and (F) presence of TDO NPs8 under UV irradiation.

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In the beginning, the MB dye degradation was monitored without a catalyst. The results show that the MB degradation without a catalyst for a sample of TDO NPs3 is 6.49%, under identical conditions within 50 min, which is represented in Figure 9D. In the case of TDO NPs5, 8.44% MB degradation was observed within 70 min, as shown in Figure 9E, whereas in the case of sample TNO NPs8, 9.74% MB degradation occurred, as shown in Figure 9F. Our results are compared with other reported literature studies on degradation of MB and Rh-B dyes and are represented in Table 2.
Table 2. Comparison of Photocatalytic Degradation of MB and Rh-B Dyes with Different Nanocatalysts
pollutant dyesmaterial usedcon. NPs/dyesize/shapetime (min)deg. (%)references
MBspindle-like TiO2100.0050–70 nm/spindle-like12062.70 (33)
 SnO2/SnO NPs50.0014–70 nm/spherical shape18090.28 (34)
 CuO microsphere33.3331 nm/flower-shaped36095.03 (35)
 Sr doped ZnO nano-catalyst33.3325–45nm/hexagonal12078.50 (36)
 ZnO + rGO nano-catalyst33.3315–35 nm/spherical shape12092.50 (37)
 Cu/MMT nano-catalyst31.268 nm/spherical shape12095.06 (38)
 TDO-nano-catalyst33.335.14 nm/spherical shape5099.35present work
Rh-BZnO–SnO2 composite104.3830 nm/nanofibers36049.00 (39)
 CuO-nanowires83.6815 nm/wire-like nano66095.00 (40)
 Fe3O4/Zn-/CuWO4 nano83.5455 nm/spherical shape21099.00 (41)
 CuO-nano catalyst50.0075 nm/microflakes300100 (42)
 SnO2 NPs40.007–14 nm/tetragonal12095.00 (43)
 ZnO nano-catalyst15.0020–30 nm/spherical shape7095.66 (44)
 TDO-nano-catalyst33.335.14 nm/spherical shape6099.28present work

4.2. PhotoDegradation of Rh-B Dye

Figure 10 presents the UV–vis absorbance spectra of Rh-B dye degradation with the TDO NPs3 nanocatalyst under UV-irradiation, where degradation was recorded at a λmax of 552 nm from 200 to 800 nm at regular time intervals. The color intensity of Rh-B significantly changed under UV irradiation. In the presence of a catalyst, Rh-B dye degraded 99.28% within 60 min under UV irradiation. The present results are similar to the degradation of RhB/MB in aqueous solution using nanosized Fe–Cd co-modified ZnO reported by Nea et al. (2018). (31) The degradation % of Rh-B dye is measured by using eq 3. Figure 10A shows the degradation of Rh-B dye (%) with the catalyst. 99.28% of Rh-B dye degraded within 60 min in the presence of TDO NPs3 as a catalyst. In the case of sample TDO NPs5, 98.56% Rh-B dye degradation was observed, as shown in Figure 10B, whereas in the case of sample TDO NPs8, 97.84% Rh-B dye degradation occurred; this is represented in Figure 10C. In the beginning, the Rh-B dye degradation was monitored without a catalyst. The results show that the Rh-B degradation without a catalyst is 5.75, 7.19, and 9.35% with respective times 60, 80, and 120 min, as shown in Figure 10D–F under identical conditions. The present results are compared with those reported in the literature for the degradation of dyes using nanocatalysts (see Table 2).

Figure 10

Figure 10. UV–vis absorption spectra of RhB dye degradation (A) in the presence of TDO NPs3, (B) in the presence of TDO NPs5, and (C) in the presence of TDO NPs8 under UV irradiation and percentage of RhB dye degradation with catalysts and without catalysts in the (D) presence of TDO NPs3, (E) presence of TDO NPs5, and (F) presence of TDO NPs8 under UV irradiation.

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4.3. Photocatalytic Activity of P25 Nanomaterials for Degradation of MB and Rh-B Dyes

The photocatalytic activity of the standard commercial photocatalyst (P25 NPs) was tested for degradation of MB/Rh-B. Therefore, the photocatalytic activity of P25 NPs was observed in the presence of UV light (λmax = 365 nm) irradiation for the degradation of MB and Rh-B. Figure 11A,B demonstrates the absorbance spectra of MB and Rh-B dye degradation at regular time intervals (30 min) that were recorded in the range of 200–800 nm. In the presence of a commercial photocatalyst, MB dye degraded 98.64% within 150 min (Figure 11C) and Rh-B dye degraded 89.87% within 180 min (Figure 11D). (32)

Figure 11

Figure 11. UV–vis absorption spectra of MB dye degradation (A) and Rh-B dye degradation (B) in the presence of commercial P25 NPs and percentage MB dye degradation (C) and percentage Rh-B dye degradation (D) under UV light irradiation.

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The results of this investigation were compared to those published on the degradation of MB and Rh-B dyes by taking into account the ratio of the TDO nanocatalyst dose to dye concentration (mg/mg), NP size and shape, degradation efficiency, and time (min) in each case (Table 2). Likewise, using the SnO/SnO2 hybrid photocatalyst, spindle-like TiO2, ZnO with the reduced graphene oxide nanocatalyst, and copper NPs on matrix-assisted montmorillonite clays, the nanocatalysis of MB dye degradation has been observed. (33−38)Table 2 summarizes the results reported for ZnO–SnO2 composites, CuO-nanowires, Fe3O4/Zn-/CuWO4 nanocatalysts, and ZnO nanocatalysts for the degradation of Rh-B. (39−44) The degradation duration is obviously dependent on the ratio of the TDO nanocatalyst dose to dye concentration (mg/mg), as well as the size and shape of the NPs (Table 2). Previous research has shown that UV irradiation of MB and Rh-B in the presence of nanophotocatalysts produces a large amount of reactive oxygen species (ROS), which reacts with the dyes to produce non-toxic products such as water molecules, carbon dioxide, and mineral acids, confirming our findings (Table 2). As a result, compared to other findings (Table 2), the synthesized TDO NPs had a higher degrading efficiency due to their smaller particle size and homogeneous spherical shape. As a result of the degradation experiment, we observed that MB degraded in 50 min at a rate of 0.31387 min–1, while Rh-B degraded in 60 min at a rate of 0.42525 min–1. Under UV irradiation, photocatalytic dye degradation studies were carried out with 20 mg of catalyst and 60 mL of dye solution (10 mg/L). Similarly, a photocatalytic experiment was conducted with various catalyst doses and dye molecule starting concentrations, and the rate constant was calculated (Table 2). As a result, the synthesized TDO NPs demonstrated excellent photocatalytic activity and may be used to degrade poisonous and hazardous organic pollutant dyes.

4.4. Effect of the Catalyst Dose on Dye Degradation

MB and Rh-B dye degradation was carried out with various sample TDO NPs-3 catalyst doses (10, 20, and 30 mg) at a constant concentration of MB/Rh-B dyes (10 mg/L). The photodegradation efficiency of MB increased from 98.05 to 99.41%, and in a similar way, the Rh-B dye degradation efficiency increased from 97.82 to 99.27% with an increase in the catalyst dose, respectively (Table 3). Photocatalytic dye degradation followed a pseudo-first-order kinetic model as given using the following expression 4.
(4)
where “r” is the degradation rate of MB/Rh-B, C is the concentration of MB/Rh-B solution, K is the adsorption coefficient of MB/Rh-B, t is the time taken for the degradation, and k is the reaction rate constant. For low initial concentrations (C0 = 10 mg/L in this experiment), this equation can be approximated to a pseudo-first-order model for ZnS:CdS nanocatalyst-mediated photodegradation of MB dye. (45) As the dose of nanocatalysts increases, the generation of free radicals and the rate constant of the reaction increase, that is, shorter time is required for complete degradation of dyes (Figure 12A,C.

Figure 12

Figure 12. Kinetic plots of MB and Rh-B dye degradation: (A) MB degradation kinetic curves for various catalyst doses (10–30 mg), (B) effect of dye concentration (5–15 mg/L) on the degradation of MB dye, (C) Rh-B degradation kinetic curves for various catalyst doses (10–30 mg), and (D) effect of dye concentration (5–15 mg/L) on the degradation of Rh-B dye.

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Table 3. Effect of Catalyst Doses and Dye Concentration on MB and Rh-B Dye Degradation
pollutant namecon. TDO NPs (mg)/dye (mg)time (min)deg. (%)rate constant (k) min–1
MB16.668097.980.08546
 33.335099.350.14263
 50.004099.420.22911
 66.664098.840.24252
 33.335099.350.14263
 22.227097.630.07227
Rh-B16.668097.090.12942
 33.336099.280.22605
 50.004098.120.35426
 66.664098.440.34087
 33.336099.280.22605
 22.229096.540.15418

4.5. Effect of Dye Concentration

The effect of dye concentrations (5, 10, and 15 mg/L) on degradation of MB/Rh-B dye was observed at a constant photocatalyst dose of the TDO NPs3 sample (20 mg). The photodegradation efficiency of MB/Rh-B decreased with increasing dye concentration/doses with respect to time intervals at a constant dose of photocatalysts (Table 3) under UV irradiation, loading with 20 mg of TDO NPs3 sample. Figure 12B,D shows the degradation rate of MB/Rh-B dyes under identical experimental conditions. Chen et al. (2017) proposed a similar photodegradation of dye solution at a constant catalyst dose for ZnO NPs under UV light irradiation. (46)

4.6. Plausible Mechanism of Dye Degradation

The feasible dramatically represented mechanism of dye degradation was studied for the TDO NPs considering that they are semiconductors and act as a photocatalyst for the degradation of MB/Rh-B dyes (see Scheme 1). Initially, UV irradiation in the presence of TDO NPs generates reactive oxygen species (ROS). Similar situation occurs with ZnO NPs degrading Cong red dye under UV irradiation. (47)

Scheme 1

Scheme 1. Schematic Representation for the Mechanism of Dye Degradation by Semiconducting TDO NPs Acting as Photocatalysts for the Degradation of MB/Rh-B Dyes
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It is assumed that TiO2 NPs (Eg = 3.02 eV) excite electrons to the conduction band via valence bands under UV irradiation and generates an electron–hole pair. The conduction band electrons react with oxygen to form superoxide ions (•O̅2) and the positive holes interact with water molecules to generate hydroxyl radicals (•OH) (see eqs 5–9). The generated ROS interacts with dye molecules, leading to degradation to carbon dioxide and water molecules, which are non-toxic. The cleavage of H2O2 results in hydroxyl radicals (•OH), and the photoelectrons reduce the oxygen (O2) adsorbed on the photocatalyst surface to produce superoxide radicals (•O̅2). Eventually, hydroxyl radicals (•OH) and superoxide ions (•O̅2) oxidize/degrade dyes to produce carbon dioxide and water molecules (see eqs 10–14). Zangeneh et al. (2015) reported dye degradation using the radical mechanism under UV irradiation. (48) A similar mechanism was proposed for the degradation of MO and Rh-B dyes after UV irradiation by using ZnO NPs as catalysts. (49) The possible mechanism was proposed that is represented in Figure 13. From the results, we concluded that the lower-band gap energy sample (TDO NPs3) shows a quick electron transfer from the valence band to the conduction band, and it shows better results of MB/Rh-B dye degradation within a short period.

Figure 13

Figure 13. Possible mechanism for MB and Rh-B dye gradation.

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5. Conclusions

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Tinanium dioxide nanoparticles in the anatase phase have been successfully synthesized using an aqueous extract from agro-waste durva grass without the use of toxic chemicals or solvents. The XRD patterns endorse the formation of the crystalline nature of the anatase phase TDO NPs. The average crystallite sizes of the NPs are 6, 8, 26, and 64 nm for the TDO NPs3, TDO NPs5, TDO NPs8, and commercial P25 NP samples, respectively. Further identification by FT-IR spectroscopy shows that the strong stretching vibration at around 420–450 cm–1 corresponds to the metal and oxygen bond (Ti-O). HR-TEM images showed spherical shape of all the samples, with average sizes 5.14, 12.54, and 29.61 nm, respectively. The TDO NPs3 sample has a significantly higher zeta potential value (−41.5 eV) compared to that of sample TDO NPs8 (−33.7 eV). Therefore, smaller size of the TDO NPs3 shows the higher stability of NPs. Thermal stability was checked by the TGA technique, which shows that the sample TDO NPs8 exhibits less weight than sample TDO NPs3. The smallest sample (TDO NPs3) has the lowest band gap energy (Eg ∼ 3.02 eV) under UV irradiation. The TDO NPs3 sample shows good photocatalytic performance for the degradation of MB and Rh-B dyes, with 99.35% degradation within 50 min and 99.28% degradation within 60 min, respectively. Therefore, the TDO NPs3 sample shows better photocatalytic activity than the TDO NPs5, TDO NPs8, and commercial P25 NP samples for the degradation of MB/Rh-B. Eventually, when the amount of catalysts increases from 10 to 30 mg, the rate constant increases and the degradation time decreases. However, when the dye concentration increases from 5 to 15 mg/L, the rate constant gradually decreases and the duration of degradation time increases. As a result, TDO NPs could be used as an effective photocatalyst for the decomposition of toxic dyes in the environment.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c01763.

  • Reusability and stability investigation of TDO NPs and GC-MS analysis of phyto-chemicals (PDF)

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Author Information

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  • Corresponding Authors
    • Badal Kumar Mandal - Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India;  Email: [email protected]
    • Luis De Los Santos Valladares - Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE 2, U.K.;  School of Materials Science and Engineering, Northeastern University, No 11, Lane 3, Wenhua Road, Heping District, Shenyang, Liaoning 110819, People’s Republic of China;  Orcidhttps://orcid.org/0000-0001-5930-9916;  Email: [email protected]
    • Pratap Kollu - CASEST, School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India;  Orcidhttps://orcid.org/0000-0001-6250-9396;  Email: [email protected]
  • Authors
    • Boya Palajonnala Narasaiah - CASEST, School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India;  Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima 15081, Peru
    • Pravallika Banoth - School of Physics, University of Hyderabad, Prof. C. R Rao Road, Gachibowli, Hyderabad 500046, Telangana, India
    • Angel Guillermo Bustamante Dominguez - Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima 15081, Peru
    • Challa Kiran Kumar - Technology Mission Division, Department of Science and Technology, Ministry of Science and Technology, MoS&T, New Delhi 110030, India
    • Crispin H. W. Barnes - Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE 2, U.K.
  • Author Contributions

    B.P.N. and P.B. are equally contributing first authors.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This work has been supported by the “Incorporacion de Investigadores program” CONCYTEC-FONDECYT. UNMSM (contract no. 12-2019-FONDECYT-BM-INC.INV.). P.K. and P.B. thank the funding from the Institute of Eminence (UoH-IoE-RC2-21-017), University of Hyderabad, India. Major and key developments of this work were performed at the University of Hyderabad, India

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    Reported is the fabrication of nickel nanospaced electrodes by electroplating and electromigration for nanoelectronic devices. Using a conventional electrochem. cell, nanogaps can be obtained by controlling the plating time alone and after a careful optimization of electrodeposition parameters such as electrolyte bath, applied potential, cleaning, etc. During the process, the gap width decreases exponentially with time until the electrode gaps are completely bridged. Once the bridge is formed, the ex situ electromigration technique can reopen the nanogap. When the gap is ≈1 nm, tunneling current-voltage characterization shows asymmetry which can be cor. by an external magnetic field. This suggests that charge transfer in the nickel electrodes depends on the orientation of magnetic moments.
  6. 6
    Nuñez, J. A. P.; Salapare, H. S.; Villamayor, M. M. S.; De Los Santos Valladares, L.; Ramos, H. J. Photodegradation of rhodamine 6G by amorphous TiO2 films grown on polymethylmethacrylate by magnetron sputtering. Prot. Met. Phys. Chem. Surf. 2017, 53, 1022– 1027,  DOI: 10.1134/s207020511706017x
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    Photodegradation of Rhodamine 6G by Amorphous TiO2 Films Grown on Polymethylmethacrylate by Magnetron Sputtering
    Nunez, Julius Andrew P.; Salapare, Hernando S., III; Villamayor, Michelle Marie S.; Valladares, Luis De Los Santos; Ramos, Henry J.
    Protection of Metals and Physical Chemistry of Surfaces (2017), 53 (6), 1022-1027CODEN: PMPCBR; ISSN:2070-2051. (Pleiades Publishing, Ltd.)
    Titanium dioxide (TiO2) was deposited on polymethylmethacrylate (PMMA) substrates by magnetron sputtering using a Compact Planar Magnetron sputtering device at different flow rate ratios of O2/Ar. The deposited TiO2 on PMMA substrates were characterized using X-ray Diffraction anal., XPS, Fourier Transform IR Spectroscopy, UV-Visible Spectroscopy, and SEM. These techniques confirm the deposition of a chem. stable amorphous TiO2 layer on the PMMA surface. Photocatalytic activity of the amorphous TiO2 layers were tested via photodegrdn. of Rhodamine 6G (Rh6G) dye soln. The samples were able to degrade 18-27% of the Rh6G soln. after the initial 25 min of UV irradn. and complete degrdn. of Rh6G was obsd. after 7 h of UV irradn.
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    Mori, T.; Hegmann, T. Determining the composition of gold nanoparticles: a compilation of shapes, sizes, and calculations using geometric considerations. J. Nanopart. Res. 2016, 18, 295,  DOI: 10.1007/s11051-016-3587-7
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    Determining the composition of gold nanoparticles: a compilation of shapes, sizes, and calculations using geometric considerations
    Mori Taizo; Hegmann Torsten
    Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology (2016), 18 (10), 295 ISSN:1388-0764.
    ABSTRACT: Size, shape, overall composition, and surface functionality largely determine the properties and applications of metal nanoparticles. Aside from well-defined metal clusters, their composition is often estimated assuming a quasi-spherical shape of the nanoparticle core. With decreasing diameter of the assumed circumscribed sphere, particularly in the range of only a few nanometers, the estimated nanoparticle composition increasingly deviates from the real composition, leading to significant discrepancies between anticipated and experimentally observed composition, properties, and characteristics. We here assembled a compendium of tables, models, and equations for thiol-protected gold nanoparticles that will allow experimental scientists to more accurately estimate the composition of their gold nanoparticles using TEM image analysis data. The estimates obtained from following the routines described here will then serve as a guide for further analytical characterization of as-synthesized gold nanoparticles by other bulk (thermal, structural, chemical, and compositional) and surface characterization techniques. While the tables, models, and equations are dedicated to gold nanoparticles, the composition of other metal nanoparticle cores with face-centered cubic lattices can easily be estimated simply by substituting the value for the radius of the metal atom of interest. GRAPHICAL ABSTRACT:
  8. 8
    Wang, W. K.; Chen, J. J.; Zhang, X.; Huang, Y. X.; Li, W. W.; Yu, H. Q. Self-induced synthesis of phase-junction TiO2 with a tailored rutile to anatase ratio below phase transition temperature. Sci. Rep. 2016, 6, 20491,  DOI: 10.1038/srep20491
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    Self-induced synthesis of phase-junction TiO2 with a tailored rutile to anatase ratio below phase transition temperature
    Wang, Wei-Kang; Chen, Jie-Jie; Zhang, Xing; Huang, Yu-Xi; Li, Wen-Wei; Yu, Han-Qing
    Scientific Reports (2016), 6 (), 20491CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
    The surface phase junction of nanocryst. TiO2 plays an essential role in governing its photocatalytic activity. Thus, facile and simple methods for prepg. phase-junction TiO2 photocatalysts are highly desired. In this work, we show that phase-junction TiO2 is directly synthesized from Ti foil by using a simple calcination method with hydrothermal soln. as the precursor below the phase transition temp. Moreover, the ratio of rutile to anatase in the TiO2 samples could be readily tuned by changing the ratio of wt. of Ti foil to HCl, which is used as the hydrothermal precursor, as confirmed by the X-ray diffraction anal. In the photocatalytic reaction by the TiO2 nanocomposite, a synergistic effect between the two phases within a certain range of the ratio is clearly obsd. The results suggest that an appropriate ratio of anatase to rutile in the TiO2 nanocomposite can create more efficient solid-solid interfaces upon calcination, thereby facilitating interparticle charge transfer in the photocatalysis.
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    Naama, S.; Hadjersi, T.; Menari, H.; Nezzal, G.; Ahmed, L. B.; Lamrani, S. Enhancement of the tartrazine photodegradation by modification of silicon nanowires with metal nanoparticles. Mater. Res. Bull. 2016, 76, 317– 326,  DOI: 10.1016/j.materresbull.2015.12.046
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    Enhancement of the tartrazine photodegradation by modification of silicon nanowires with metal nanoparticles
    Naama, Sabrina; Hadjersi, Toufik; Menari, Hamid; Nezzal, Ghania; Ahmed, Latefa Baba; Lamrani, Sabrina
    Materials Research Bulletin (2016), 76 (), 317-326CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
    In this work we investigated the tartrazine photodegrdn. by modified and unmodified silicon nanowires (SiNWs). SiNWs were elaborated by one-step metal-assisted electroless chem. etching of silicon substrate in HF/AgNO3 aq. soln. The modification of SiNWs was carried out by nanoparticles of platinum, palladium, silver, gold and copper in chem. solns. of PtO2, PdCl2, AgNO3, AuCl3 and CuSO4, resp. The results show that Cu-modified silicon nanowires give the highest photocatalytic activity compared to the unmodified SiNWs and SiNWs modified with nanoparticles of Au, Pt, Pd and Ag.
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    Dhand, C.; Dwivedi, N.; Loh, X. J.; Jie Ying, A. N. J.; Verma, N. K.; Beuerman, R. W.; Lakshminarayanan, S.; Ramakrishna, S. Methods and strategies for the synthesis of diverse nanoparticles and their applications: a comprehensive overview. RSC Adv. 2015, 5, 105003– 105037,  DOI: 10.1039/c5ra19388e
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    Methods and strategies for the synthesis of diverse nanoparticles and their applications: a comprehensive overview
    Dhand, Chetna; Dwivedi, Neeraj; Loh, Xian Jun; Jie Ying, Alice Ng; Verma, Navin Kumar; Beuerman, Roger W.; Lakshminarayanan, Rajamani; Ramakrishna, Seeram
    RSC Advances (2015), 5 (127), 105003-105037CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    Ongoing advances in nanotechnol. research have established a variety of methods to synthesize nanoparticles (NPs) from a diverse range of materials, including metals, semiconductors, ceramics, metal oxides, polymers, etc. Depending upon their origin and synthesis methods, NPs possess unique physicochem., structural and morphol. characteristics, which are important in a wide variety of applications concomitant to electronic, optoelectronic, optical, electrochem., environment and biomedical fields. This review provides a comprehensive overview on various phys., chem. and bio-assisted methods largely employed to synthesize and fabricate NPs of varying size, surface characteristics, functionalities and physicochem. behavior. The key applications of nanoparticles have also been discussed.
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    Atarod, M.; Nasrollahzadeh, M.; Mohammad Sajadi, S. M. Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water. J. Colloid Interface Sci. 2016, 462, 272– 279,  DOI: 10.1016/j.jcis.2015.09.073
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    Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water
    Atarod, Monireh; Nasrollahzadeh, Mahmoud; Mohammad Sajadi, S.
    Journal of Colloid and Interface Science (2016), 462 (), 272-279CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
    This work reports a facile and green synthesis of Ag/TiO2 nanocomposite by ext. of leaves of Euphorbia heterophylla without any stabilizer or surfactant. The green synthesized Ag/TiO2 nanocomposite was characterized by field emission scanning electron microscope (FESEM), energy-dispersive x-ray spectroscopy (EDS), FTIR spectroscopy, X-ray diffraction anal. (XRD) and UV-visible. The Ag/TiO2 nanocomposite is effective catalyst for redn. of various dyes, such as 4-nitrophenol (4-NP), Methyl orange (MO), Congo red (CR) and Methylene blue (MB) in the presence of NaBH4 in water at room temp. Catalysis reactions were monitored by employing UV-visible spectroscopy. Catalysis reactions followed pseudo-first order rate equation. The catalyst can be recovered and reused several times without significant loss of its catalytic activity.
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    Subhapriya, S.; Gomathipriya, P. Green synthesis of titanium dioxide (TiO2) nanoparticles by Trigonella foenum-graecum extract and its antimicrobial properties. Microb. Pathog. 2018, 116, 215– 220,  DOI: 10.1016/j.micpath.2018.01.027
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    12
    Green synthesis of titanium dioxide (TiO2) nanoparticles by Trigonella foenum-graecum extract and its antimicrobial properties
    Subhapriya, S.; Gomathipriya, P.
    Microbial Pathogenesis (2018), 116 (), 215-220CODEN: MIPAEV; ISSN:0882-4010. (Elsevier Ltd.)
    In recent years, biosynthesis of nanoparticles has received considerable attention due to the growing need to develop clean and nontoxic chems., low-cost approaches, eco - friendly solvents and renewable materials. In the current study, the biosynthesis of TiO2 nanoparticles (TiO2NPs) was attained by a chem. and biosynthesized method by using the aq. leaf ext. of Trigonella foenum-graecum (TF-TiO2NP). TiO2 NPs were characterized by FTIR, UV, XRD, HR-TEM and HR-SEM methods. The X-ray diffraction displayed the existence of TF-TiO2NPs which is confirmed by the incidence of peaks at 25.28 corresponds to 101 anatase form. HR-SEM perceptions revealed that synthesized TiO2NPs were spherical in shape and the size of individual nanoparticles as well as a few aggregates was found to be 20-90 nm. The antimicrobial activities of biosynthesized nanoparticles (TF-TiO2NPs) were examd. using Kirby-Bauer method. The TF-TiO2 nanoparticles showed significant antimicrobial activity against all the tested microorganisms.
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    Sonane, M.; Moin, N.; Satish, A. The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles. Chemosphere 2017, 187, 240– 247,  DOI: 10.1016/j.chemosphere.2017.08.080
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    The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles
    Sonane, Madhavi; Moin, Nida; Satish, Aruna
    Chemosphere (2017), 187 (), 240-247CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
    The exponential increase in the usage of engineered nanoparticles (ENPs) has raised global concerns due to their potential toxicity and environmental impacts. Nano-TiO2 and nano-ZnO have been extensively used in various applications. Thus, there is a need for detg. the toxic potentials of ENPs as well as, to develop the possible attenuation method for ENPs toxicity. Both in the in vitro and in vivo systems, exposure to the majority of ENPs have shown Reactive Oxygen Species (ROS) generation, which leads to oxidative stress mediated inflammation, genotoxicity, and cytotoxicity. Hence, with the rationale of detg. easy and economical protection against ENPs exposure, the amelioration effect of the antioxidants (curcumin and vitamin-C) against the nano-TiO2 and nano-ZnO induced ROS and lethality were investigated in Caenorhabditis elegans. We not only employed pre-treatment and along with treatment approach, but also detd. the effect of antioxidants at different time points of treatment. Our study revealed that both the antioxidants efficiently ameliorate nanoparticles induced ROS as well as lethality in worms. Further, the pretreatment approach was more effective than the along with treatment. Therefore, our study indicates the possibility of evading the nanotoxicity by incorporating curcumin and vitamin-C in everyday diet.
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    Li, M.; He, W.; Liu, Y.; Wu, H.; Wamer, W. G.; Lo, Y. M.; Yin, J. J. FD&C Yellow No.5 (tartrazine) degradation via reactive oxygen species triggered by TiO2 and Au/TiO2 nanoparticles exposed to simulated sunlight. J. Agric. Food Chem. 2014, 62, 12052– 12060,  DOI: 10.1021/jf5045052
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    14
    FD&C Yellow No. 5 (Tartrazine) Degradation via Reactive Oxygen Species Triggered by TiO2 and Au/TiO2 Nanoparticles Exposed to Simulated Sunlight
    Li, Meng; He, Weiwei; Liu, Yi; Wu, Haohao; Wamer, Wayne G.; Lo, Y. Martin; Yin, Jun-Jie
    Journal of Agricultural and Food Chemistry (2014), 62 (49), 12052-12060CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
    When exposed to light, TiO2 nanoparticles (NPs) become photoactivated and create electron/hole pairs as well as reactive oxygen species (ROS). We examd. the ROS prodn. and degrdn. of a widely used azo dye, FD&C Yellow No. 5 (tartrazine), triggered by photoactivated TiO2 NPs. Degrdn. was found to follow pseudo-first order reaction kinetics where the rate const. increased with TiO2 NP concn. Depositing Au on the surface of TiO2 largely enhanced electron transfer and ROS generation, which consequently accelerated dye degrdn. Alk. conditions promoted ROS generation and dye degrdn. Results from ESR spin-trap spectroscopy suggested that at pH 7.4, both hydroxyl radical (•OH) and singlet oxygen (1O2) were responsible for dye discoloration, whereas at pH 5, the consumption of 1O2 became dominant. Implications for dye degrdn. in foods and other consumer products that contain both TiO2 and FD&C Yellow No. 5 as ingredients are discussed.
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    Al-Tohamy, R.; Ali, S. S.; Li, F.; Okasha, K. M.; Mahmoud, Y. A. G.; Elsamahy, T.; Jiao, J.; Fu, Y.; Sun, J. A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety. Ecotoxicol. Environ. Saf. 2022, 231, 113160,  DOI: 10.1016/j.ecoenv.2021.113160
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    A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety
    Al-Tohamy, Rania; Ali, Sameh S.; Li, Fanghua; Okasha, Kamal M.; Mahmoud, Yehia A.-G.; Elsamahy, Tamer; Jiao, Haixin; Fu, Yinyi; Sun, Jianzhong
    Ecotoxicology and Environmental Safety (2022), 231 (), 113160CODEN: EESADV; ISSN:0147-6513. (Elsevier B.V.)
    A review. The synthetic dyes used in the textile industry pollute a large amt. of water. Textile dyes do not bind tightly to the fabric and are discharged as effluent into the aquatic environment. As a result, the continuous discharge of wastewater from a large no. of textile industries without prior treatment has significant neg. consequences on the environment and human health. Textile dyes contaminate aquatic habitats and have the potential to be toxic to aquatic organisms, which may enter the food chain. This review will discuss the effects of textile dyes on water bodies, aquatic flora, and human health. Textile dyes degrade the esthetic quality of bodies of water by increasing biochem. and COD, impairing photosynthesis, inhibiting plant growth, entering the food chain, providing recalcitrance and bioaccumulation, and potentially promoting toxicity, mutagenicity, and carcinogenicity. Therefore, dye-contg. wastewater should be effectively treated using eco-friendly technologies to avoid neg. effects on the environment, human health, and natural water resources. This review compares the most recent technologies which are commonly used to remove dye from textile wastewater, with a focus on the advantages and drawbacks of these various approaches. This review is expected to spark great interest among the research community who wish to combat the widespread risk of toxic org. pollutants generated by the textile industries.
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    Lellis, B.; Fávaro-Polonio, C. Z.; Pamphile, J. A.; Polonio, J. C. Effects of textile dyes on health and the environment and bioremediation potential of living organisms. Biotechnol. Res. Innov. 2019, 3, 275– 290,  DOI: 10.1016/j.biori.2019.09.001
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    Ranjan, P.; Singh, R. K.; Suematsu, H.; Phillip, L.; Sarathi, R. Synthesis of nano-ZnO by wire explosion process and its photocatalytic activity. J. Environ. Chem. Eng. 2017, 5, 1676– 1684,  DOI: 10.1016/j.jece.2017.02.036
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    Synthesis of nano-ZnO by wire explosion process and its photocatalytic activity
    Ranjan, Prem; Singh, Raj Kamal; Suematsu, H.; Phillip, Ligy; Sarathi, R.
    Journal of Environmental Chemical Engineering (2017), 5 (2), 1676-1684CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
    Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized through X-ray diffraction (XRD) studies and by TEM studies. The particle size anal. indicates that they follow log-normal distribution and the mean size of the ZnO nanoparticles formed is about 44 nm. Optical band gap of ZnO is found to be 3.21 eV by UV-vis diffuse reflectance spectroscopy (DRS). The synthesized ZnO nano particles were used as photo catalyst for degrdn. of methylene blue (MB) in aq. soln. Nano zinc oxide of 100 mg/L was found as the optimum quantity for UV photo degrdn. of 10 mg/L MB. ZnO nanoparticles were verified for its reusability. The results of the study are compared with com. ZnO nanoparticle and with Degussa P-25 TiO2. LC-MS studies were carried out to identify the intermediates and degrdn. pathway.
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    Ribeiro, J. P.; Nunes, M. I. Recent trends and developments in Fenton processes for industrial wastewater treatment–A critical review. Environ. Res. 2021, 197, 110957,  DOI: 10.1016/j.envres.2021.110957
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    Recent trends and developments in Fenton processes for industrial wastewater treatment - A critical review
    Ribeiro, Joao Peres; Nunes, Maria Isabel
    Environmental Research (2021), 197 (), 110957CODEN: ENVRAL; ISSN:0013-9351. (Elsevier Inc.)
    A review. This study reviews the recent developments in the application of Fenton processes in real industrial wastewater treatment, focusing on heterogeneous catalysts and catalyst regeneration/reuse. This article presents the features, inherent advantages or drawbacks, and primary exptl. results obtained on established and emerging Fenton processes, highlighting the course of innovations and current scenario in a research field that has recently undergone rapid transition. Therefore, a comprehensive literature survey was conducted to review studies published over the last decade dealing with application of Fenton processes to industrial wastewater treatment. The research in this field is primarily focused on discovering or synthesizing new materials to substitute conventional iron salt Fenton catalysts and/or regenerate and reuse the spent catalyst, in contrast to optimizing the application of existing materials. Hence, the emphasis is on producing reusable materials, transitioning from linear to circular economy. Some of the major challenges identified herein include analyzing or improving heterogeneous catalyst lifetime, detg. the predominant pathway of heterogeneous and homogeneous catalysis to pollutant degrdn., and defining the best layout to incorporate Fenton processes into full-scale treatment plants, particularly its coupling with biol. treatment.
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    Jing, X.; Yuan, J.; Cai, D.; Li, B.; Hu, D.; Li, J. Concentrating and recycling of high-concentration printing and dyeing wastewater by a disc tube reverse osmosis-Fenton oxidation/low temperature crystallization process. Sep. Purif. Technol. 2021, 266, 118583,  DOI: 10.1016/j.seppur.2021.118583
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    19
    Concentrating and recycling of high-concentration printing and dyeing wastewater by a disc tube reverse osmosis-Fenton oxidation/low temperature crystallization process
    Jing, Xinjun; Yuan, Junsheng; Cai, Daniu; Li, Bin; Hu, Dongliang; Li, Jianyang
    Separation and Purification Technology (2021), 266 (), 118583CODEN: SPUTFP; ISSN:1383-5866. (Elsevier B.V.)
    A novel three-step process consisting of disk tube reverse osmosis (DTRO), Fenton oxidn., and low temp. crystn. is described for the treatment of printing and dyeing wastewater. The DTRO step was used to further conc. the wastewater obtained from a nanofiltration (NF) treatment. The desalinated water can be directly reused in the prodn. process, and the COD, TOC, TDS, and SO2-4 concns. of the concd. wastewater were above 1500 mg/L, 500 mg/L, 150 g/L, and 100 g/L, resp. The concd. wastewater was then treated by Fenton oxidn., and the COD, TOC, and chroma removal rates in this step were over 80%, 80%, and nearly 100%, resp. Finally, when the crystn. end point temp. was 0°C, the recovery and purity of the product were above 60% and 99%, resp. For the small amt. of Cl- contained in the cryst. mother liquor, the Cl- and SO2-4 in the mother liquor were sepd. by NF and then sent back to the DTRO step to be re-concd. The degrdn. of org. compds. in wastewater was studied by UV-Vis spectroscopy, three-dimensional fluorescence spectroscopy (3D-EEM), and total org. carbon analyzer. The cryst. products were characterized by X-ray diffraction. The results showed that this new coupling process can realize high reuse of printing and dyeing wastewater.
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    Siripireddy, B.; Mandal, B. K. Facile green synthesis of zinc oxide nanoparticles by Eucalyptus globulus and their photocatalytic and antioxidant activity. Adv. Powder Technol. 2017, 28, 785– 797,  DOI: 10.1016/j.apt.2016.11.026
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    Facile green synthesis of zinc oxide nanoparticles by Eucalyptus globulus and their photocatalytic and antioxidant activity
    Siripireddy, Balaji; Mandal, Badal Kumar
    Advanced Powder Technology (2017), 28 (3), 785-797CODEN: APTEEE; ISSN:0921-8831. (Elsevier B.V.)
    Eucalyptus globulus leaf ext. mediated synthesis of spherical zinc oxide nanoparticles (ZnO NPs) was carried out under ambient conditions. UV-Visible studies of the synthesized nanoparticles revealed the characteristic peak at 361 nm indicating the formation of ZnO nanoparticles. Powder X-ray Diffractometric (XRD) study showed the strong, intense and narrow-width diffraction peaks indicating the formation of cryst. nanoparticles with most stable hexagonal phase. Field emission-SEM (FE-SEM) and high resoln.-transmission electron microscopic (HR-TEM) results confirmed the formation of spherical ZnO NPs with mean particle size of 11.6 nm which is in close agreement with XRD pattern. Further, energy dispersive X-ray diffraction anal. (EDAX) revealed the formation of highly pure ZnO NPs with the peaks of Zn and O atoms. ZnO NPs exhibited effective photocatalytic activity in degrading Methylene blue and Methyl orange with max. degrdn. efficiency up to 98.3% at 30 mg of catalyst doses. In addn., ZnO NPs exhibited high antioxidant activity against DPPH free radicals scavenger.
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    Spada, E. R.; Pereira, E. A.; Montanhera, M. A.; Morais, L. H.; Freitas, R. G.; Costa, R. G.; Soares, F. R.; Ribeiro, C.; de Paula, F. R. Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route. J. Mater. Sci.: Mater. Electron. 2017, 28, 16932– 16938,  DOI: 10.1007/s10854-017-7613-z
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    Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route
    Spada, Edna R.; Pereira, Eder A.; Montanhera, Maykon A.; Morais, Leonardo H.; Freitas, Renato G.; Costa, Rodrigo G. F.; Soares, Gabriela B.; Ribeiro, Caue; de Paula, Fernando R.
    Journal of Materials Science: Materials in Electronics (2017), 28 (22), 16932-16938CODEN: JSMEEV; ISSN:0957-4522. (Springer)
    Titanium dioxide (TiO2) is used in a range of applications such as photocatalysis and sensor devices. In this work, TiO2 nanoparticles (TiO2NPs) in the crystallog. forms anatase and rutile were prepd. by the green route. The method involves dissolving titanium oxysulfate (TiOSO4) powder in hydrogen peroxide (H2O2) soln. and subsequent thermal treatment of the resultant amorphous ppt. X-ray diffraction (XRD) was used to follow the structural evolution of the amorphous ppt., and microstructure anal. was realized with Rietveld refinement. In addn., the photocatalytic activity of the synthesized TiO2NPs was evaluated by studying the degrdn. of Rhodamine B (RhB) dye. The highest photocatalytic activity was obsd. for TiO2 obtained at 600°C in the crystallog. form anatase.
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    Gowri, S.; Rajiv Gandhi, R.; Senthil, S.; Suresh, J.; Sundrarajan, M. Enhancing Antimicrobial Activity of Biotemplated TiO2 Nanoparticles Using Aloe Vera Plant Extract. J. Bionanosci. 2016, 10, 181– 190,  DOI: 10.1166/jbns.2016.1344
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    Enhancing antimicrobial activity of biotemplated TiO2 nanoparticles using aloe vera plant extract
    Gowri, S.; Rajiv Gandhi, R.; Senthil, S.; Suresh, J.; Sundrarajan, M.
    Journal of Bionanoscience (2016), 10 (3), 181-190CODEN: JBOIE2; ISSN:1557-7910. (American Scientific Publishers)
    Nowadays, the growth of metal oxide nanoparticles in an eco-friendly manner by plant materials has attracted significant attention. This investigation aims at the synthesis of TiO2 nanoparticles using ext. derived from the Aloe vera plant for the alternative of synthetic pptg. agents, surfactants and solvents like sodium hydroxide, sodium lauryl sulfate and ethanol etc., resp. These biosynthesized metal oxide nanoparticles have a wide range of biol. applications. However, this chapter discusses only on the antimicrobial activities. Addnl., TiO2 nanoparticles were treated on cotton fabric and their efficacy against bacterial and fungal strains were also discussed. This subsequently resulted in powerful antimicrobial activities. The result shows that the coated fabric demonstrated significant antibacterial activity against S. aureus than E. coli due to the attraction of generated active oxygen species of TiO2 with S. aureus. Both samples are produced more potent against C. albicans as well as A. niger fungal strains. The current simple synthetic method aims to provide nanosized materials with well cryst. structure, good optical properties and superior antimicrobial activity using cheap precursor of Aloe vera ext.
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    Aravind, M.; Amalanathan, M.; Mary, M. Synthesis of TiO2 nanoparticles by chemical and green synthesis methods and their multifaceted properties. SN Appl. Sci. 2021, 3, 409,  DOI: 10.1007/s42452-021-04281-5
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    Synthesis of TiO2 nanoparticles by chemical and green synthesis methods and their multifaceted properties
    Aravind, M.; Amalanathan, M.; Mary, M. Sony Michael
    SN Applied Sciences (2021), 3 (4), 409CODEN: SASNBO; ISSN:2523-3971. (Springer International Publishing AG)
    In this present work, Titanium dioxide nanoparticles (TiO2 NPs) successfully synthesized using the chem. as well as the green synthesis routine. The ethanol provoked the chem. redn. of ions. In the green synthesis, jasmine flower ext. was used as a reducing and stabilizing agent because it contains alkaloids, coumarins, flavonoids. The Rutile phase of TiO2 NPs with an av. cryst. size of 31-42 nm was revealed from the XRD pattern. From the UV-Visible spectroscopy, the optically active region of TiO2 NPs at 385 nm represents the visible region spectrum. The Ti-O-Ti and Ti-O vibration bond formation confirms the formation of TiO2 NPs. The SEM image of TiO2 NPs reveals that the spherical shaped NPs with randomly arranged manner. The obtained results have revealed that the property of TiO2 nanoparticles was similar in both processes. The Photodegrdn. of methylene blue dye was investigated and resulted in the max. degrdn. efficiency of 92% is achieved at 120 min of irradn. The Photodegrdn. study shows the biosynthesized TiO2 NPs exhibits a higher degrdn. efficiency compared to chem. synthesized TiO2 NPs. The antibacterial activity of prepd. TiO2 NP's was studied using grams-pos. and gram-neg. strains. The biol. activities of green synthesized TiO2 NPs are enhanced compared to the chem. synthesized TiO2 NPs. Hence the degrdn. efficiency and zone inhibition layer indicate that the prepd. TiO2 NPs are the potential candidate for environmental and biomedical applications.
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    Al-hamoud, K.; Shaik, M. R.; Khan, M.; Alkhathlan, H. Z.; Adil, S. F.; Kuniyil, M.; Assal, M.; Al-Warthan, A.; Siddiqui, M. R. H.; Tahir, M. N.; Khan, S. T.; Mousa, A. A.; Khan, M. Pulicaria undulata Extract-Mediated Eco-Friendly Preparation of TiO2 Nanoparticles for Photocatalytic Degradation of Methylene Blue and Methyl Orange. ACS Omega 2022, 7, 4812– 4820,  DOI: 10.1021/acsomega.1c05090
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    24
    Pulicaria undulata Extract-Mediated Eco-Friendly Preparation of TiO2 Nanoparticles for Photocatalytic Degradation of Methylene Blue and Methyl Orange
    Al-hamoud, Khaleel; Shaik, Mohammed Rafi; Khan, Merajuddin; Alkhathlan, Hamad Z.; Adil, Syed Farooq; Kuniyil, Mufsir; Assal, Mohamed E.; Al-Warthan, Abdulrahman; Siddiqui, Mohammed Rafiq H.; Tahir, Muhammad Nawaz; Khan, Shams Tabrez; Mousa, Ahmad Amine; Khan, Mujeeb
    ACS Omega (2022), 7 (6), 4812-4820CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
    Eco-friendly approaches for the prepn. of nanomaterials have recently attracted considerable attention of scientific community due to rising environmental distresses. The aim of the current study is to prep. titanium dioxide (TiO2) nanoparticles (NPs) using an eco-friendly approach and investigate their performance for the photocatalytic degrdn. of hazardous org. dyes. For this, TiO2 NPs were prepd. by using the aq. ext. of the Pulicaria undulata (L.) plant in a single step at room temp. Energy-dispersive X-ray spectroscopy established the presence of both titanium and oxygen in the sample. X-ray diffraction revealed the formation of cryst., anatase-phase TiO2 NPs. On the other hand, transmission election microscopy confirmed the formation of spherical shaped NPs. The presence of residual phytomols. as capping/stabilization agents is confirmed by UV-vis anal. and Fourier-transform IR spectroscopy. Indeed, in the presence of P. undulata, the anatase phase of TiO2 is stabilized at a significantly lower temp. (100°C) without using any external stabilizing agent. The green synthesized TiO2 NPs were used to investigate their potential for the photocatalytic degrdn. of hazardous org. dyes including methylene blue and methyl orange under UV-visible light irradn. Due to the small size and high dispersion of NPs, almost complete degrdn. (~ 95%) was achieved in a short period of time (between 1 and 2 h). No significant difference in the photocatalytic activity of the TiO2 NPs was obsd. even after repeated use (three times) of the photocatalyst. Overall, the green synthesized TiO2 NPs exhibited considerable potential for fast and eco-friendly removal of harmful org. dyes.
  25. 25
    Abodif, A. M.; Meng, L.; Ma, S.; Ahmed, A. S.; Belvett, N.; Wei, Z. Z.; Ning, D. Mechanisms and models of adsorption: TiO2-supported biochar for removal of 3, 4-dimethylaniline. ACS Omega 2020, 5, 13630– 13640,  DOI: 10.1021/acsomega.0c00619
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    Mechanisms and Models of Adsorption: TiO2-Supported Biochar for Removal of 3,4-Dimethylaniline
    Abodif, Ahmed M.; Meng, Li; MA, Sanjrani; Ahmed, Abdelaal S. A.; Belvett, Norville; Wei, Zhan Zhi; Ning, Du
    ACS Omega (2020), 5 (23), 13630-13640CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
    3,4-dimethylaniline (3,4-DMA) was selected as a representative org. aniline compd. A biochar-TiO2 (BC-TiO2) composite was prepd. by sol-gel process to assess its adsorption ability for 3,4-DMA. Simultaneously, the composite adsorption ability and physicochem. properties were examd. Isotherm studies confirmed 3,4-DMA adsorption by BC and BC-TiO2 composite agreed with Langmuir and Toth adsorption models, which meant formation of a 3,4-DMA monolayer on sorbent surfaces. The max. 3,4-DMA adsorption capacity was 322.58 and 285.71 mg/g for BC and BC-TiO2, resp. Adsorption kinetics showed the 3,4-DMA adsorption process on BC and BC-TiO2 composite was controlled by a pseudo-second-order kinetic model with R2 = 0.99.
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    Pushpamalini, T.; Keerthana, M.; Sangavi, R.; Nagaraj, A.; Kamaraj, P. Comparative analysis of green synthesis of TiO2 nanoparticles using four different leaf extract. Mater. Today: Proc. 2021, 40, S180– S184,  DOI: 10.1016/j.matpr.2020.08.438
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    Comparative analysis of green synthesis of TiO2 nanoparticles using four different leaf extract
    Pushpamalini, T.; Keerthana, M.; Sangavi, R.; Nagaraj, A.; Kamaraj, P.
    Materials Today: Proceedings (2021), 40 (Suppl._1), S180-S184CODEN: MTPAC4; ISSN:2214-7853. (Elsevier Ltd.)
    Green synthesis of nano materials has gained a great attention of current researchers owing to its less toxicity, reproducibility, pollution free, economic and low energy process. Green synthesis of Titanium dioxide (TiO2) nanoparticle was carried out using four different leaf exts. The leaf exts. of Piper betel, Ocimum tenuiflorum, Moringa oleifera, Coriandrum sativum were used as reducing agents to synthesize TiO2 from Titanium tetraisopropoxide. The synthesized TiO2 nanoparticle was then characterized by X-Ray Diffraction (XRD), Fourier Transform-IR Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) and SEM (SEM) techniques. The spectroscopic and microscopic techniques confirmed the formation, size and shape of the TiO2 nano particle. Further the differences in phys. and morphol. characteristics of synthesized nanoparticle incurred with the different with the usage of different leaf ext. was analyzed and justified. The differences in the photocatalytic efficiency of synthesized TiO2 nanoparticles were studied by degrading Malachite green dye. Out of the four dyenanomaterials used, TiO2 synthesized using Moringa oleifera leaf ext. was found to have greater efficiency when compared to other three leaf exts.
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    Demir, E.; Creus, A.; Marcos, R. Titanium dioxide and zinc oxide nanoparticles are not mutagenic in the mouse lymphoma assay but modulate the mutagenic effect of UV-C-light post-treatment. Fresen. Environ. Bull. 2017, 26, 1001– 1016
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    Gautam, A.; Kshirsagar, A.; Biswas, R.; Banerjee, S.; Khanna, P. K. Photodegradation of organic dyes based on anatase and rutile TiO2 nanoparticles. RSC Adv. 2016, 6, 2746– 2759,  DOI: 10.1039/c5ra20861k
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    Photodegradation of organic dyes based on anatase and rutile TiO2 nanoparticles
    Gautam, Ashish; Kshirsagar, Anuraj; Biswas, Rahul; Banerjee, Shaibal; Khanna, Pawan K.
    RSC Advances (2016), 6 (4), 2746-2759CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    The present work highlights a simple nanochem. based clean and efficient process for effective degrdn. of various org. dyes by use of anatase and rutile TiO2 nanoparticles. Based on photodegrdn. studies it was obsd. that at certain exptl. parameters, rutile TiO2 was as effective as anatase for the degrdn. of indigo carmine (IC) dye in aq. soln. However, anatase TiO2 was found to be much more efficient against methylene blue (MB), methyl orange (MO), rhodamine B (RB) and eriochrome black T (EBT) under short UV irradn. The photodegrdn. study of these org. dyes was also performed under long UV irradn. employing both anatase and rutile titania and the results showed similar trends. However, only EBT photodegrdn. indicated equal photocatalytic activity by both phases. The catalytic degrdn. of the org. dyes was studied by degrdn. kinetics. The max. degrdn. efficiency using anatase and rutile titania photocatalysts was found to be 88% and 77% in the case of MB under short UV irradn. while about 65% was found in the case of EBT under long UV irradn. The reuse of photocatalyst even after five cycles retained the degrdn. efficiency of 83% and 71% resp. for anatase and rutile when tested against MB.
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    Dodoo-Arhin, D.; Buabeng, F. P.; Mwabora, J. M.; Amaniampong, P. N.; Agbe, H.; Nyankson, E.; Obada, D. O.; Asiedu, N. Y. The effect of titanium dioxide synthesis technique and its photocatalytic degradation of organic dye pollutants. Heliyon 2018, 4, e00681  DOI: 10.1016/j.heliyon.2018.e00681
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    Diallo, A.; Manikandan, E.; Rajendran, V.; Maaza, M. Physical & enhanced photocatalytic properties of green synthesized SnO2 nanoparticles via Aspalathus linearis. J. Alloys Compd. 2016, 681, 561– 570,  DOI: 10.1016/j.jallcom.2016.04.200
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    Physical & enhanced photocatalytic properties of green synthesized SnO2 nanoparticles via Aspalathus linearis
    Diallo, A.; Manikandan, E.; Rajendran, V.; Maaza, M.
    Journal of Alloys and Compounds (2016), 681 (), 561-570CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    This contribution reports on the synthesis and the main phys. properties of n-type SnO2 nanoparticles synthesized for the first time by a completely green chem. process using Aspalathus linearis's natural ext. as an effective chelating agent. Their surface/interface and vol. properties by X-rays diffraction, Raman, X-rays photoemission and photoluminescence spectroscopies are reported. Their av. diam. ranging from 2.1 to 19.3 nm follows a thermal governed equation of 〈Oparticles〉 = 1.048 10-5 T2 - 4.92 10-3 T + 2.84. The smallest SnO2 nanoparticles exhibit effective photocatalytic responses to Methylene blue, Congo red and Eosin Y.
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    Nea, D.; Kondamareddy, K. K.; Bin, H.; Lu, D.; Kumar, P.; Dwivedi, R. K.; Pelenovich, D.; Zhao, X.-Z.; Gao, W.; Fu, D. Enhanced visible light photodegradation activity of RhB/METHYLENE BLUE from aqueous solution using nanosized novel Fe-Cd co-modified ZnO. Sci. Rep. 2018, 8, 10691,  DOI: 10.1038/s41598-018-29025-1
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    Tammina, S. K.; Mandal, B. K.; Kadiyala, N. K. Photocatalytic Degradation of Methylene Blue Dye by Nonconventional synthesized SnO2 Nanoparticles. Environ. Nanotechnol. Monit. Manag. 2018, 10, 339– 350,  DOI: 10.1016/j.enmm.2018.07.006
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    Arunkumar, S.; Alagiri, M. Synthesis and Characterization of Spindle-Like TiO2 Nanostructures and Photocatalytic Activity on Methyl Orange and Methyl Blue Dyes Under Sunlight Radiation. J. Cluster Sci. 2017, 28, 2635– 2643,  DOI: 10.1007/s10876-017-1245-6
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    Synthesis and Characterization of Spindle-Like TiO2 Nanostructures and Photocatalytic Activity on Methyl Orange and Methyl Blue Dyes Under Sunlight Radiation
    Arunkumar, S.; Alagiri, M.
    Journal of Cluster Science (2017), 28 (5), 2635-2643CODEN: JCSCEB; ISSN:1040-7278. (Springer)
    Spindle-like TiO2 nanostructures was prepd. by a simple one pot solvothermal method followed by calcination at 400°C for 3 h. The sample was characterized using various techniques such as X-ray diffractometer, transmission electron microscopy, Fourier transform IR spectroscopy and UV-Vis absorption spectroscopy. The crystal structure of TiO2 nanostructure was measured by X-ray diffractometer. According to the XRD result, the peaks in the sample can be indexed to anatase phase of TiO2. The morphol. characterization of TiO2 sample was examd. by transmission electron microscopy. The synthesized sample consisted of spindle-like shape with size in the range of 50-70 nm. The band gap value of Spindle-like TiO2 nanostructures is 2.92 eV, which is lower than that of bulk TiO2 of 3.2 eV. The FTIR bands obsd. at 493, 443 and 428 cm-1 confirms the presence of TiO2. The Spindle-like TiO2 nanostructures showed photodegrdn. ability for methyl orange and methyl blue dye. The reuse evaluation of the Spindle-like TiO2 nanostructures showed that their photocatalytic activity had good durability.
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    Santhi, K.; Rani, C.; Karuppuchamy, S. Synthesis and characterization of a novel SnO/SnO2 hybrid photocatalyst. J. Alloys Compd. 2016, 662, 102– 107,  DOI: 10.1016/j.jallcom.2015.12.007
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    Synthesis and characterization of a novel SnO/SnO2 hybrid photocatalyst
    Santhi, K.; Rani, C.; Karuppuchamy, S.
    Journal of Alloys and Compounds (2016), 662 (), 102-107CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
    Nanostructured SnO/SnO2 hybrid material was successfully synthesized by microwave irradn. method. X-ray diffraction spectroscopy shows the formation of SnO/SnO2 nanocomposite material. Nanosphere morphol. of the nanocomposite was obsd. by SEM. UV-visible diffuse reflectance spectra demonstrate that the light absorption capacity of SnO/SnO2 nanocomposite was extended to the visible region. The photocatalytic activity of SnO/SnO2 nanocomposite was investigated by the degrdn. of Methylene blue under UV light irradn. The effect of SnO/SnO2 nanocomposite dose, dye concn., pH and irradn. time for photodegrdn. of Methylene blue dye was also studied. SnO/SnO2 nanocomposite exhibits higher photocatalytic activity in neutral pH.
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    Mageshwari, K.; Sathyamoorthy, R.; Park, J. Photocatalytic activity of hierarchical CuO microspheres synthesized by facile reflux condensation method. Powder Technol. 2015, 278, 150– 156,  DOI: 10.1016/j.powtec.2015.03.004
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    Photocatalytic activity of hierarchical CuO microspheres synthesized by facile reflux condensation method
    Mageshwari, K.; Sathyamoorthy, R.; Park, Jinsub
    Powder Technology (2015), 278 (), 150-156CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
    Flower-shaped hierarchical CuO microspheres consisting of interpenetrating nanosheets were successfully synthesized by reflux condensation method without using any surfactant or templates. X-ray diffraction revealed the formation of single phase CuO exhibiting monoclinic crystal structure. SEM and transmission electron microscopy confirmed the formation of hierarchical flower-shaped CuO microspheres made up of nanosheets as building blocks. UV-vis diffused reflectance spectroscopy showed a steep absorption between 700 and 950 nm, and the corresponding band gap of CuO nanoparticles was found to be 1.59 eV. To explore the potential capability of flower-shaped CuO microspheres for wastewater treatment, the photocatalytic activity of CuO nanostructures was evaluated by monitoring the photodegrdn. of methyl orange (MO) and methylene blue (MB) dyes in the presence of hydrogen peroxide under UV light irradn. Exptl. results demonstrated that CuO hierarchical architecture possesses good photocatalytic activity towards MO and MB dyes, indicating the feasibility of using CuO for the effective removal of org. contaminants from wastewater.
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    Yousefi, R.; Jamali-Sheini, F.; Cheraghizade, M.; Khosravi-Gandomani, S.; Sáaedi, A.; Huang, N. M.; Basirun, M.; Azarang, M. Enhanced visible-light photocatalytic activity of strontium-doped zinc oxide nanoparticles. Mater. Sci. Semicond. Process. 2015, 32, 152– 159,  DOI: 10.1016/j.mssp.2015.01.013
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    Enhanced visible-light photocatalytic activity of strontium-doped zinc oxide nanoparticles
    Yousefi, Ramin; Jamali-Sheini, Farid; Cheraghizade, Mohsen; Khosravi-Gandomani, Sara; Saaedi, Abdolhossein; Huang, Nay Ming; Basirun, Wan Jefrey; Azarang, Majid
    Materials Science in Semiconductor Processing (2015), 32 (), 152-159CODEN: MSSPFQ; ISSN:1369-8001. (Elsevier Ltd.)
    Strontium-doped zinc oxide nanoparticles (Zn1-xSrxO NPs; x=0, 0.02, 0.04, and 0.06) were synthesized by a sol-gel method. Transmission electron microscopy (TEM) and SEM (SEM) images showed NPs with nearly spherical shapes, with sizes from 27 to 41 nm for high Sr concn. and undoped ZnO NPs, resp. X-ray diffraction (XRD) patterns, selected area electron diffraction (SAED) patterns, and Raman spectra indicated that the undoped and Sr-doped ZnO NPs were crystd. in a hexagonal wurtzite structure. However, the Raman results revealed a decrease in the cryst. quality with an increase in the Sr concn. in the ZnO structure. Evidence of dopant incorporation is demonstrated by XPS of the Sr-doped ZnO NPs. From the results of optical characterizations, the band-gap values of the Zn0.98Sr0.02O and Zn0.96Sr0.04O NPs decreased, while the band-gap value of the Zn0.94Sr0.06O NPs increased in comparison to the band-gap value of the undoped ZnO NPs. Finally, the obtained NPs were used as a photocatalyst to remove methylene blue (MB). Observations showed that the efficiency of the photocatalyst activity of the ZnO NPs was significantly increased by increasing the Sr, but until an optimum concn.
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    Azarang, M.; Shuhaimi, A.; Yousefi, R.; Jahromi, S. P. One-pot sol–gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of Methylene Blue. RSC Adv. 2015, 5, 21888– 21896,  DOI: 10.1039/c4ra16767h
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    One-pot sol-gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of Methylene Blue
    Azarang, Majid; Shuhaimi, Ahmad; Yousefi, Ramin; Jahromi, Siamak Pilban
    RSC Advances (2015), 5 (28), 21888-21896CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    ZnO NPs + reduced graphene oxide (rGO) nanocomposites were synthesized using a sol-gel method with starch as the polymn. agent. Long-chain starch compds. were used to terminate the growth of the ZnO NPs on rGO and stabilize them. The resulting products were annealed at 350 °C to remove the starch and produce a reduced graphene oxide (rGO) sheet in one-pot without any post-annealing processes. Microscopic studies showed that the NPs were dispersed on the rGO sheet. They had a spherical shape and a size of approx. 25 ± 10 nm. In addn., these studies revealed that the NPs were single crystals. The X-ray diffraction pattern of the NPs indicated a hexagonal (wurtzite) structure. The results of Fourier transform IR spectrum anal. (FTIR) revealed that the GO sheet was transformed into rGO via the sol-gel method in the starch environment. The results of photoluminescence spectroscopy demonstrated that the incorporation of reduced graphene oxide (rGO) sheets with ZnO NPs suppressed the electron-hole recombination of the composite. Therefore, a significant enhancement in the photocatalytic degrdn. of methylene blue (MB) was obsd. with the ZnO NPs + rGO nanocomposite compared to the bare ZnO nanoparticles.
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    Mekewi, M. A.; Darwish, A. S.; Amin, M. S.; Eshaq, G.; Bourazan, H. A. Copper nanoparticles supported onto montmorillonite clays as efficient catalyst for methylene blue dye degradation. Egypt. J. Pet. 2016, 25, 269– 279,  DOI: 10.1016/j.ejpe.2015.06.011
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    Pascariu, P.; Airinei, A.; Olaru, N.; Olaru, L.; Nica, V. Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers. Ceram. Int. 2016, 42, 6775– 6781,  DOI: 10.1016/j.ceramint.2016.01.054
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    Photocatalytic degradation of Rhodamine B dye using ZnO-SnO2 electrospun ceramic nanofibers
    Pascariu, Petronela; Airinei, Anton; Olaru, Niculae; Olaru, Liliana; Nica, Valentin
    Ceramics International (2016), 42 (6), 6775-6781CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
    ZnO-SnO2 nanofibers were fabricated by the electrospinning technique combined with calcination at 600 °C. Their structural and morphol. properties were analyzed by X-ray diffraction and scanning/transmission electron microscopy, and their photocatalytic activity was investigated by the degrdn. of Rhodamine B (RhB) dye by visible light irradn. UV-vis spectral data were used to est. the photodegrdn. efficiency of the metal oxide nanocomposites. All the RhB dye samples were tested for six hours of degrdn. the highest efficiency being obtained for a molar ratio Sn/Zn of 0.030.
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    Wang, L.; Zhou, Q.; Zhang, G.; Liang, Y.; Wang, B.; Zhang, W.; Lei, W.; Wang, W. A facile room temperature solution-phase route to synthesize CuO nanowires with enhanced photocatalytic performance. Mater. Lett. 2012, 74, 217– 219,  DOI: 10.1016/j.matlet.2012.01.123
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    A facile room temperature solution-phase route to synthesize CuO nanowires with enhanced photocatalytic performance
    Wang, Lijuan; Zhou, Qing; Zhang, Guling; Liang, Yujie; Wang, Baoshun; Zhang, Weiwei; Lei, Bo; Wang, Wenzhong
    Materials Letters (2012), 74 (), 217-219CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    CuO nanowires have been prepd. with high yield at low cost by a facile room temp. soln. phase route. The compn., morphol. and size of the as-prepd. CuO nanowires were characterized by powder X-ray diffraction (XRD), SEM, and transmission electron microscopy (TEM). The UV-vis absorption spectra demonstrate that the as-prepd. CuO nanowires exhibit quantum size confinement effects. The photocatalytic properties of CuO nanowires were further investigated by evaluating on photo-degrdn. of a simulation, physicochem. pollutant rhodamine B (RhB). The exptl. results indicated that CuO nanowires have enhanced photocatalytic performance with 95.5% decompn. of RhB after 9 h reaction under UV light irradn., which was much higher than that of com. CuO powders (39.6%).
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    Shekofteh-Gohari, M.; Habibi-Yangjeh, A. Fabrication of novel magnetically separable visible-light-driven photocatalysts through photosensitization of Fe3O4/ZnO with CuWO4. J. Ind. Eng. Chem. 2016, 44, 174– 184,  DOI: 10.1016/j.jiec.2016.08.028
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    Fabrication of novel magnetically separable visible-light-driven photocatalysts through photosensitization of Fe3O4/ZnO with CuWO4
    Shekofteh-Gohari, Maryam; Habibi-Yangjeh, Aziz
    Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2016), 44 (), 174-184CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
    In this work, we have successfully fabricated ternary Fe3O4/ZnO/CuWO4 nanocomposites with different wt. percentages of CuWO4 by refluxing method. The visible-light photocatalytic activity of the Fe3O4/ZnO/CuWO4 nanocomposites was investigated using Rhodamine B. It was found that the photocatalytic activity of the nanocomposites significantly depends on the wt. percentage of CuWO4. Among the prepd. samples, the nanocomposite with 40% of CuWO4 displayed the highest activity. The superior photocatalytic ability of the Fe3O4/ZnO/CuWO4 (40%) nanocomposite compared to the binary Fe3O4/ZnO and Fe3O4/CuWO4 photocatalysts in degrdn. of methylene blue, as another org. dye, under visible-light irradn. was also confirmed.
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    Tadjarodi, A.; Akhavan, O.; Bijanzad, K. Photocatalytic activity of CuO nanoparticles incorporated in mesoporous structure prepared from bis (2-aminonicotinato) copper (II) microflakes. Trans. Nonferrous Met. Soc. China 2015, 25, 3634– 3642,  DOI: 10.1016/s1003-6326(15)64004-3
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    Photocatalytic activity of CuO nanoparticles incorporated in mesoporous structure prepared from bis(2-aminonicotinato) copper(II) microflakes
    Tadjarodi, Azadeh; Akhavan, Omid; Bijanzad, Keyvan
    Transactions of Nonferrous Metals Society of China (2015), 25 (11), 3634-3642CODEN: TNMCEW; ISSN:1003-6326. (Elsevier B.V.)
    An easy method for prepg. CuO nanoparticles incorporated in a mesoporous structure was presented based on the thermal decompn. of a copper complex. The novel copper coordination compd. of [Cu(anic)2]·0.75H2O (anic= 2-aminonicotinate) with the microflake morphol. was synthesized through the reaction of 2-aminonicotinic acid (Hanic) and copper(II) nitrate. Using elemental anal. and Fourier transform IR (FTIR) spectroscopy, the chem. compn. of CuC12H11.5N4O4.75 was proposed. Calcination process at 550 °C for 4 h transformed the microflakes into CuO nanoparticles incorporated in a mesoporous structure. The FTIR peaks assigned to 2-aminonicotinate were completely removed after calcination, confirming CuO formation. X-ray diffraction (XRD) anal. also confirmed the generation of pure and cryst. CuO. SEM showed CuO nanoparticles with the av. diam. of 75 nm. The diffuse reflectance spectrum (DRS) of the CuO nanoparticles showed a band gap energy of -1.58 eV. The degrdn. efficiency toward rhodamine B was almost 100 % after 5 h illumination when both CuO and H2O2 were utilized. The results show that the product can be used as an efficient photocatalyst for water treatment.
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    Fu, L.; Zheng, Y.; Ren, Q.; Wang, A.; Deng, B. Green biosynthesis of SnO2 nanoparticles by plectranthus amboinicus leaf extract their photocatalytic activity toward rhodamine B degradation. J. Ovonic Res. 2015, 11, 21– 26
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    Green biosynthesis of SnO2 nanoparticles by plectranthus amboinicus leaf extract their photocatalytic activity toward rhodamine b degradation
    Fu, L.; Zheng, Y.; Ren, Q.; Wang, A.; Deng, B.
    Journal of Ovonic Research (2015), 11 (1), 21-26CODEN: JOROAK; ISSN:1584-9953. (National Institute of Materials Physics)
    In this paper, we report the first time prepn. of SnO2 nanoparticles (NPs) using a green chem. method. The leaf ext. of Plectranthus amboinicus was used as reducing and stabilization agent for synthesizing SnO2 NPs. The synthesized SnO2 NPs were characterized by SEM, EDX, XRD and UV-vis spectroscopy. Results showed that the biosynthesized SnO2 NPs owing a high purity. The photocatalytic property of the biosynthesized SnO2 NPs was investigated by photodegrdn. of rhodamine B (Rh B) under visible light illumination. Results indicated that the photocatalytic performance of the biosynthesized SnO2 NPs is much higher than that of com. SnO2. Moreover, the biosynthesized SnO2 also exhibited an excellent reusability.
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    Rahman, Q. I.; Ahmad, M.; Misra, S. K.; Lohani, M. Effective photocatalytic degradation of rhodamine B dye by ZnO nanoparticles. Mater. Lett. 2013, 91, 170– 174,  DOI: 10.1016/j.matlet.2012.09.044
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    Effective photocatalytic degradation of Rhodamine B dye by ZnO nanoparticles
    Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi
    Materials Letters (2013), 91 (), 170-174CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
    Highly cryst. ZnO nanoparticles (NPs) were synthesized with Zn acetate as precursor and oxalic acid at 80° C through the simple soln. phase approach. The synthesized ZnO NPs possessed monodispersity with the av. size 20-30 nm. The cryst. properties revealed the typical hexagonal wurtzite phase with orientation along c-axis. The photocatalytic activity investigation was carried out by performing the decompn. of Rhodamine-B dye under UV illumination over as-synthesized ZnO NPs. The Rhodamine B dye considerably degraded by ∼95% within 70 min in the presence of as-synthesized ZnO NPs. An excellent rate const. (k = 0.0343 min-1) was obtained for the degrdn. of Rhodamine B dye.
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    Soltani, N.; Saion, E.; Hussein, M. Z.; Erfani, M.; Abedini, A.; Bahmanrokh, G.; Navasery, P.; Vaziri, P. Visible light-induced degradation of methylene blue in the presence of photocatalytic ZnS and CdS nanoparticles. Int. J. Mol. Sci. 2012, 13, 12242– 12258,  DOI: 10.3390/ijms131012242
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    Visible light-induced degradation of methylene blue in the presence of photocatalytic ZnS and CdS nanoparticles
    Soltani, Nayereh; Saion, Elias; Hussein, Mohd. Zobir; Erfani, Maryam; Abedini, Alam; Bahmanrokh, Ghazaleh; Navasery, Manizheh; Vaziri, Parisa
    International Journal of Molecular Sciences (2012), 13 (), 12242-12258CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)
    ZnS and CdS nanoparticles were prepd. by a simple microwave irradn. method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal cryst. structures, resp. The band gap energies of ZnS and CdS nanoparticles were estd. using UV-visible absorption spectra to be about 4.22 and 2.64 eV, resp. Photocatalytic degrdn. of methylene blue was carried out using phys. mixts. of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradn. The residual concn. of methylene blue soln. was monitored using UV-visible absorption spectrometry. From the study of the variation in compn. of ZnS:CdS, a compn. of 1:4 (by wt.) was found to be very efficient for degrdn. of methylene blue. In this case the degrdn. efficiency of the photocatalyst nanoparticles after 6 h irradn. time was about 73% with a reaction rate of 3.61 × 10-3 min-1. Higher degrdn. efficiency and reaction rate were achieved by increasing the amt. of photocatalyst and initial pH of the soln.
  46. 46
    Chen, X.; Wu, Z.; Liu, D.; Gao, Z. Preparation of ZnO photocatalyst for the efficient and rapid photocatalytic degradation of azo dyes. Nanoscale Res. Lett. 2017, 12, 143,  DOI: 10.1186/s11671-017-1904-4
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    Preparation of ZnO Photocatalyst for the Efficient and Rapid Photocatalytic Degradation of Azo Dyes
    Chen Xiaoqing; Wu Zhansheng; Liu Dandan; Gao Zhenzhen
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    Zinc oxide (ZnO) photocatalysts were synthesized by sol-gel method using zinc acetate as precursor for degradation of azo dyes under UV irradiation. The resultant samples were characterized by different techniques, such as XRD, SEM, and EDX. The influence of preparation conditions such as calcination temperature and composite ratio on the degradation of methyl orange (MO) was investigated. ZnO prepared with a composite ratio of 4:1 and calcination temperature of 400 °C exhibited 99.70% removal rate for MO. The effect of operation parameters on the degradation was also studied. Results showed that the removal rate of azo dyes increased with the increased dosage of catalyst and decreased initial concentration of azo dyes and the acidic condition is favorable for degradation. Furthermore, the kinetics and scavengers of the reactive species during the degradation were also investigated. It was found that the degradation of azo dyes fitted the first-order kinetics and superoxide ions were the main species. The proposed photocatalyst can efficiently and rapidly degrade azo dyes; thus, this economical and environment-friendly photocatalyst can be applied to the treatment of wastewater contaminated with synthetic dyes.
  47. 47
    Vidya, C.; Manjunatha, C.; Chandraprabha, M. N.; Rajshekar, M.; Raj, A. R. Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications. J. Environ. Chem. Eng. 2017, 5, 3172– 3180,  DOI: 10.1016/j.jece.2017.05.058
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    Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications
    Vidya., C.; Manjunatha., C.; Chandraprabha., M. N.; Rajshekar, Megha; Raj. M. A. L, Antony
    Journal of Environmental Chemical Engineering (2017), 5 (4), 3172-3180CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
    The present study describes the use Artocarpus Heterophyllus leaves ext. for the synthesis of Zinc oxide nanoparticles (ZnO NPs). The particles were calcined at 400, 600 and 800°C for 1 h. Powder X-Ray Diffraction (PXRD) results showed the ZnO NPs calcined at different temp. to be cryst. with hexagonal wurtzite phase. The morphol. was studied using SEM (SEM) and elemental compn. investigated using energy dispersive spectroscopy (EDS) showed peaks for Zn and O only. The exact size of ZnO particles and its cryst. nature were investigated from transmission electron microscopy (TEM),High resoln. transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The TEM showed the size range of the ZnO NPs to be ∼10-15 nm at 400°C, ∼15-25 nm at 600°C and ∼25-30 at 800°C which are in good agreement with the SEM observation. The band gap energy was calcd. from UV diffuse reflectance spectra and found to be 3.42, 3.38 and 3.35 eV for 400, 600 and 800°C resp. The fourier transform infra-red spectroscopy (FTIR) spectra of leaf ext. confirmed the presence of phyto constituents such as amines, amides, quinines and ketones in the leaf ext. The ZnO NPs calcined at 400°C having higher band gap energy and smaller size was used for photocatalytic degrdn. The studies showed the efficiency greater than 90% towards degrdn. of 20 ppm Congo red dye soln. at 0.24 g/L ZnO NPs in 1 h at pH 9.
  48. 48
    Zangeneh, H.; Zinatizadeh, A. A. L.; Habibi, M.; Akia, M.; Hasnain Isa, M. H. Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review. J. Ind. Eng. Chem. 2015, 26, 1– 36,  DOI: 10.1016/j.jiec.2014.10.043
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    Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review
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    Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2015), 26 (), 1-36CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
    This article compares the effectiveness of pure and modified TiO2 for photocatalytic degrdn. of different org. matters and clarifies the advantages of the modified TiO2 with photoactivity under visible light. Photocatalytic degrdn. technique with titanium dioxide is generally applied for treating wastewater contg. refractory org. contaminants with the purpose of reuse due to its ability to achieve complete mineralization of the compds. under mild conditions such as ambient temp. and pressure. Performance of different types of photocatalytic reactors, effects of important parameters on the reactors performance, effect of various methods used to enhance the photocatalytic activity of TiO2 including doping, sensitization of TiO2 and surface modification are discussed in details. So far, a few review papers have been published and extensive information have been reported on the structure and electronic properties of TiO2, difference between TiO2 with other common semiconductors used for photocatalytic applications, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling, the effects of various operating parameters on the photocatalytic degrdn. of phenols and dyes and types of reactors, comparison between effective modes of TiO2 application as immobilized on surface or as suspension, and photocatalytic hybrid membrane system are presented. However, in the published review papers, performance of the different modified photocatalysts is rarely compared quant. Therefore, in order to provide an inclusive and effective comparison among the studies, specific removal rate (SRR) (mg compd.removed/g cat. h) was calcd. as a response.
  49. 49
    Ban, J. J.; Xu, G. C.; Zhang, L.; Lin, H.; Sun, Z. P.; Lv, Y.; Jia, D. Z. Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes. J. Solid State Chem. 2017, 256, 151– 157,  DOI: 10.1016/j.jssc.2017.09.002
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    Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes
    Ban, Jin-jin; Xu, Guan-cheng; Zhang, Li; Lin, He; Sun, Zhi-peng; Lv, Yan; Jia, Dian-zeng
    Journal of Solid State Chemistry (2017), 256 (), 151-157CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
    A cube-like porous ZnO architecture was synthesized by direct two-step thermolysis of a zinc-based metal-org. framework [(CH3)2NH2][Zn(HCOO)3]. The obtained ZnO microcube was characterized by powder X-ray diffraction, SEM, transmission electron microscopy and nitrogen adsorption and desorption isotherms. The mesoporous ZnO microcube was comprised by many nanoparticles, and inherited the cube shape from [(CH3)2NH2][Zn(HCOO)3] precursor. With large surface area and mesoporous structure, the ZnO microcube exhibits excellent photocatalytic activities against methyl orange (MO) and rhodamine B (RhB) under UV irradn., and the degrdn. rates reached 99.7% and 98.1% within 120 min, resp.

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  • Abstract

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    Figure 1

    Figure 1. UV–visible absorption spectra of TDO NPs after annealing (A) sample at 300 °C, (B) sample at 500 °C, and (C) sample at 800 °C and (D) band gap energy of TDO NPs from 300 to 800 °C.

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    Figure 2

    Figure 2. XRD pattern of TDO NPs annealed at 300 °C (A), 500 °C (B), and 800 °C (C), without annealing (D), and commercial P25 NPs (E).

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    Figure 3

    Figure 3. FT-IR spectra of (A) durva grass extract (B) TDO NPs3 annealed at 300 °C, (C) TDO NPs5 annealed at 500 °C, and (D) TDO NPs8 annealed at 800 °C.

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    Figure 4

    Figure 4. HR-TEM images of the TDO NPs3 sample annealed at 300 °C: (A) 10 nm magnification (B) 50 nm magnification, and (C) 100 nm magnification, (D) interplanar distance d values of the lattice, and (E) SAED pattern of TDO NPs and (F) existing elements in the synthesized TDO NPs.

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    Figure 5

    Figure 5. HR-TEM images of the TDO NPs5 sample annealed at 500 °C under (A) 20 nm magnification, (B) 50 nm magnification, and (C) 100 nm magnification, (D) interplanar distance d value of the lattice, (E) SAED pattern of TDO NPs, and (F) existing elements in the synthesized TDO NPs.

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    Figure 6

    Figure 6. HR-TEM images of the TDO NPs8 sample annealed at 800 °C (A) under (B) 100 nm magnification (C) and 200 nm magnification, (D) interplanar distance d value of the lattice, (E) SAED pattern of TDO NPs, and (F) existing elements in the synthesized TDO NPs.

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    Figure 7

    Figure 7. DLS spectrum of the TDO NP sample annealed at 300 °C (A), annealed at 500 °C (B), and annealed at 800 °C (C) and TGA spectrum of TDO NPs after annealing at 300 °C (D), annealing at 500 °C (E), and annealing at 800 °C (F).

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    Figure 8

    Figure 8. Photoluminescence spectra of TDO NPs3 (A), TDO NPs5 (B), TDO NPs8 samples (C) and commercial P25 NPs (D).

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    Figure 9

    Figure 9. UV–vis absorption spectra of MB dye degradation (A) in the presence of TDO NPs3, (B) in the presence of TDO NPs5, and (C) in the presence of TDO NPs8 under UV irradiation and percentage of MB dye degradation with catalysts and without catalysts in the (D) presence of TDO NPs3, (E) presence of TDO NPs5, and (F) presence of TDO NPs8 under UV irradiation.

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    Figure 10

    Figure 10. UV–vis absorption spectra of RhB dye degradation (A) in the presence of TDO NPs3, (B) in the presence of TDO NPs5, and (C) in the presence of TDO NPs8 under UV irradiation and percentage of RhB dye degradation with catalysts and without catalysts in the (D) presence of TDO NPs3, (E) presence of TDO NPs5, and (F) presence of TDO NPs8 under UV irradiation.

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    Figure 11

    Figure 11. UV–vis absorption spectra of MB dye degradation (A) and Rh-B dye degradation (B) in the presence of commercial P25 NPs and percentage MB dye degradation (C) and percentage Rh-B dye degradation (D) under UV light irradiation.

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    Figure 12

    Figure 12. Kinetic plots of MB and Rh-B dye degradation: (A) MB degradation kinetic curves for various catalyst doses (10–30 mg), (B) effect of dye concentration (5–15 mg/L) on the degradation of MB dye, (C) Rh-B degradation kinetic curves for various catalyst doses (10–30 mg), and (D) effect of dye concentration (5–15 mg/L) on the degradation of Rh-B dye.

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    Scheme 1

    Scheme 1. Schematic Representation for the Mechanism of Dye Degradation by Semiconducting TDO NPs Acting as Photocatalysts for the Degradation of MB/Rh-B Dyes
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    Figure 13

    Figure 13. Possible mechanism for MB and Rh-B dye gradation.

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  • References

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      A review. Nanomaterials with exceptional phys. and chem. properties are the key to the success of the next generation of gas sensor technol., which is expected to have special features like being lightwt. and flexible for wearability, mech. robustness, reliable operation with wide environmental changes, and self-powered, in addn. to the general sensor characteristics. The design of the chemiresistor with nanostructured hybrid material has indicated a great potential to meet these current demands, drawing significant attention to the technol. developments in the past decades. The nanotechnol. driven strategic design of the hybrid nanostructures is predicted to be pivotal for the development of nanomaterials bearing distinct phys. and chem. properties and catalytic power, enabling them to produce overall improvements in sensor efficiency. In this review, a comprehensive review on the recent progress of hybrid gas sensors fabricated by coupling various metal oxides and 2D materials like transition metal dichalcogenides, graphene, and its derivs. are presented. The limitations of the current materials, key challenges, as well as the futuristic strategy for material design delivering fascinating properties and modern growth techniques are highlighted. A special emphasis has been given to hybrid sensors made with transition metal dichalcogenides, which are considered to be an emerging material and very few works have reported on its hybrid with metal oxides. The relevance of reliable detection of hydrogen is felt due to the dramatic rise in the use of hydrogen in industrial, com., and household purposes. As the whole world is moving toward a hydrogen economy, reliable, accurate, and robust hydrogen sensors will be a crucial component of the technol. systems. In view of this, the current status and recent progress on hydrogen sensors based on heterostructured nanomaterials are also presented to the reader.
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      Characterization of the in Vitro Osteogenic Response to Submicron TiO2 Particles of Varying Structure and Crystallinity
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      ABSTRACT: Size, shape, overall composition, and surface functionality largely determine the properties and applications of metal nanoparticles. Aside from well-defined metal clusters, their composition is often estimated assuming a quasi-spherical shape of the nanoparticle core. With decreasing diameter of the assumed circumscribed sphere, particularly in the range of only a few nanometers, the estimated nanoparticle composition increasingly deviates from the real composition, leading to significant discrepancies between anticipated and experimentally observed composition, properties, and characteristics. We here assembled a compendium of tables, models, and equations for thiol-protected gold nanoparticles that will allow experimental scientists to more accurately estimate the composition of their gold nanoparticles using TEM image analysis data. The estimates obtained from following the routines described here will then serve as a guide for further analytical characterization of as-synthesized gold nanoparticles by other bulk (thermal, structural, chemical, and compositional) and surface characterization techniques. While the tables, models, and equations are dedicated to gold nanoparticles, the composition of other metal nanoparticle cores with face-centered cubic lattices can easily be estimated simply by substituting the value for the radius of the metal atom of interest. GRAPHICAL ABSTRACT:
    8. 8
      Wang, W. K.; Chen, J. J.; Zhang, X.; Huang, Y. X.; Li, W. W.; Yu, H. Q. Self-induced synthesis of phase-junction TiO2 with a tailored rutile to anatase ratio below phase transition temperature. Sci. Rep. 2016, 6, 20491,  DOI: 10.1038/srep20491
      8
      Self-induced synthesis of phase-junction TiO2 with a tailored rutile to anatase ratio below phase transition temperature
      Wang, Wei-Kang; Chen, Jie-Jie; Zhang, Xing; Huang, Yu-Xi; Li, Wen-Wei; Yu, Han-Qing
      Scientific Reports (2016), 6 (), 20491CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
      The surface phase junction of nanocryst. TiO2 plays an essential role in governing its photocatalytic activity. Thus, facile and simple methods for prepg. phase-junction TiO2 photocatalysts are highly desired. In this work, we show that phase-junction TiO2 is directly synthesized from Ti foil by using a simple calcination method with hydrothermal soln. as the precursor below the phase transition temp. Moreover, the ratio of rutile to anatase in the TiO2 samples could be readily tuned by changing the ratio of wt. of Ti foil to HCl, which is used as the hydrothermal precursor, as confirmed by the X-ray diffraction anal. In the photocatalytic reaction by the TiO2 nanocomposite, a synergistic effect between the two phases within a certain range of the ratio is clearly obsd. The results suggest that an appropriate ratio of anatase to rutile in the TiO2 nanocomposite can create more efficient solid-solid interfaces upon calcination, thereby facilitating interparticle charge transfer in the photocatalysis.
    9. 9
      Naama, S.; Hadjersi, T.; Menari, H.; Nezzal, G.; Ahmed, L. B.; Lamrani, S. Enhancement of the tartrazine photodegradation by modification of silicon nanowires with metal nanoparticles. Mater. Res. Bull. 2016, 76, 317– 326,  DOI: 10.1016/j.materresbull.2015.12.046
      9
      Enhancement of the tartrazine photodegradation by modification of silicon nanowires with metal nanoparticles
      Naama, Sabrina; Hadjersi, Toufik; Menari, Hamid; Nezzal, Ghania; Ahmed, Latefa Baba; Lamrani, Sabrina
      Materials Research Bulletin (2016), 76 (), 317-326CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
      In this work we investigated the tartrazine photodegrdn. by modified and unmodified silicon nanowires (SiNWs). SiNWs were elaborated by one-step metal-assisted electroless chem. etching of silicon substrate in HF/AgNO3 aq. soln. The modification of SiNWs was carried out by nanoparticles of platinum, palladium, silver, gold and copper in chem. solns. of PtO2, PdCl2, AgNO3, AuCl3 and CuSO4, resp. The results show that Cu-modified silicon nanowires give the highest photocatalytic activity compared to the unmodified SiNWs and SiNWs modified with nanoparticles of Au, Pt, Pd and Ag.
    10. 10
      Dhand, C.; Dwivedi, N.; Loh, X. J.; Jie Ying, A. N. J.; Verma, N. K.; Beuerman, R. W.; Lakshminarayanan, S.; Ramakrishna, S. Methods and strategies for the synthesis of diverse nanoparticles and their applications: a comprehensive overview. RSC Adv. 2015, 5, 105003– 105037,  DOI: 10.1039/c5ra19388e
      10
      Methods and strategies for the synthesis of diverse nanoparticles and their applications: a comprehensive overview
      Dhand, Chetna; Dwivedi, Neeraj; Loh, Xian Jun; Jie Ying, Alice Ng; Verma, Navin Kumar; Beuerman, Roger W.; Lakshminarayanan, Rajamani; Ramakrishna, Seeram
      RSC Advances (2015), 5 (127), 105003-105037CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Ongoing advances in nanotechnol. research have established a variety of methods to synthesize nanoparticles (NPs) from a diverse range of materials, including metals, semiconductors, ceramics, metal oxides, polymers, etc. Depending upon their origin and synthesis methods, NPs possess unique physicochem., structural and morphol. characteristics, which are important in a wide variety of applications concomitant to electronic, optoelectronic, optical, electrochem., environment and biomedical fields. This review provides a comprehensive overview on various phys., chem. and bio-assisted methods largely employed to synthesize and fabricate NPs of varying size, surface characteristics, functionalities and physicochem. behavior. The key applications of nanoparticles have also been discussed.
    11. 11
      Atarod, M.; Nasrollahzadeh, M.; Mohammad Sajadi, S. M. Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water. J. Colloid Interface Sci. 2016, 462, 272– 279,  DOI: 10.1016/j.jcis.2015.09.073
      11
      Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water
      Atarod, Monireh; Nasrollahzadeh, Mahmoud; Mohammad Sajadi, S.
      Journal of Colloid and Interface Science (2016), 462 (), 272-279CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
      This work reports a facile and green synthesis of Ag/TiO2 nanocomposite by ext. of leaves of Euphorbia heterophylla without any stabilizer or surfactant. The green synthesized Ag/TiO2 nanocomposite was characterized by field emission scanning electron microscope (FESEM), energy-dispersive x-ray spectroscopy (EDS), FTIR spectroscopy, X-ray diffraction anal. (XRD) and UV-visible. The Ag/TiO2 nanocomposite is effective catalyst for redn. of various dyes, such as 4-nitrophenol (4-NP), Methyl orange (MO), Congo red (CR) and Methylene blue (MB) in the presence of NaBH4 in water at room temp. Catalysis reactions were monitored by employing UV-visible spectroscopy. Catalysis reactions followed pseudo-first order rate equation. The catalyst can be recovered and reused several times without significant loss of its catalytic activity.
    12. 12
      Subhapriya, S.; Gomathipriya, P. Green synthesis of titanium dioxide (TiO2) nanoparticles by Trigonella foenum-graecum extract and its antimicrobial properties. Microb. Pathog. 2018, 116, 215– 220,  DOI: 10.1016/j.micpath.2018.01.027
      12
      Green synthesis of titanium dioxide (TiO2) nanoparticles by Trigonella foenum-graecum extract and its antimicrobial properties
      Subhapriya, S.; Gomathipriya, P.
      Microbial Pathogenesis (2018), 116 (), 215-220CODEN: MIPAEV; ISSN:0882-4010. (Elsevier Ltd.)
      In recent years, biosynthesis of nanoparticles has received considerable attention due to the growing need to develop clean and nontoxic chems., low-cost approaches, eco - friendly solvents and renewable materials. In the current study, the biosynthesis of TiO2 nanoparticles (TiO2NPs) was attained by a chem. and biosynthesized method by using the aq. leaf ext. of Trigonella foenum-graecum (TF-TiO2NP). TiO2 NPs were characterized by FTIR, UV, XRD, HR-TEM and HR-SEM methods. The X-ray diffraction displayed the existence of TF-TiO2NPs which is confirmed by the incidence of peaks at 25.28 corresponds to 101 anatase form. HR-SEM perceptions revealed that synthesized TiO2NPs were spherical in shape and the size of individual nanoparticles as well as a few aggregates was found to be 20-90 nm. The antimicrobial activities of biosynthesized nanoparticles (TF-TiO2NPs) were examd. using Kirby-Bauer method. The TF-TiO2 nanoparticles showed significant antimicrobial activity against all the tested microorganisms.
    13. 13
      Sonane, M.; Moin, N.; Satish, A. The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles. Chemosphere 2017, 187, 240– 247,  DOI: 10.1016/j.chemosphere.2017.08.080
      13
      The role of antioxidants in attenuation of Caenorhabditis elegans lethality on exposure to TiO2 and ZnO nanoparticles
      Sonane, Madhavi; Moin, Nida; Satish, Aruna
      Chemosphere (2017), 187 (), 240-247CODEN: CMSHAF; ISSN:0045-6535. (Elsevier Ltd.)
      The exponential increase in the usage of engineered nanoparticles (ENPs) has raised global concerns due to their potential toxicity and environmental impacts. Nano-TiO2 and nano-ZnO have been extensively used in various applications. Thus, there is a need for detg. the toxic potentials of ENPs as well as, to develop the possible attenuation method for ENPs toxicity. Both in the in vitro and in vivo systems, exposure to the majority of ENPs have shown Reactive Oxygen Species (ROS) generation, which leads to oxidative stress mediated inflammation, genotoxicity, and cytotoxicity. Hence, with the rationale of detg. easy and economical protection against ENPs exposure, the amelioration effect of the antioxidants (curcumin and vitamin-C) against the nano-TiO2 and nano-ZnO induced ROS and lethality were investigated in Caenorhabditis elegans. We not only employed pre-treatment and along with treatment approach, but also detd. the effect of antioxidants at different time points of treatment. Our study revealed that both the antioxidants efficiently ameliorate nanoparticles induced ROS as well as lethality in worms. Further, the pretreatment approach was more effective than the along with treatment. Therefore, our study indicates the possibility of evading the nanotoxicity by incorporating curcumin and vitamin-C in everyday diet.
    14. 14
      Li, M.; He, W.; Liu, Y.; Wu, H.; Wamer, W. G.; Lo, Y. M.; Yin, J. J. FD&C Yellow No.5 (tartrazine) degradation via reactive oxygen species triggered by TiO2 and Au/TiO2 nanoparticles exposed to simulated sunlight. J. Agric. Food Chem. 2014, 62, 12052– 12060,  DOI: 10.1021/jf5045052
      14
      FD&C Yellow No. 5 (Tartrazine) Degradation via Reactive Oxygen Species Triggered by TiO2 and Au/TiO2 Nanoparticles Exposed to Simulated Sunlight
      Li, Meng; He, Weiwei; Liu, Yi; Wu, Haohao; Wamer, Wayne G.; Lo, Y. Martin; Yin, Jun-Jie
      Journal of Agricultural and Food Chemistry (2014), 62 (49), 12052-12060CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
      When exposed to light, TiO2 nanoparticles (NPs) become photoactivated and create electron/hole pairs as well as reactive oxygen species (ROS). We examd. the ROS prodn. and degrdn. of a widely used azo dye, FD&C Yellow No. 5 (tartrazine), triggered by photoactivated TiO2 NPs. Degrdn. was found to follow pseudo-first order reaction kinetics where the rate const. increased with TiO2 NP concn. Depositing Au on the surface of TiO2 largely enhanced electron transfer and ROS generation, which consequently accelerated dye degrdn. Alk. conditions promoted ROS generation and dye degrdn. Results from ESR spin-trap spectroscopy suggested that at pH 7.4, both hydroxyl radical (•OH) and singlet oxygen (1O2) were responsible for dye discoloration, whereas at pH 5, the consumption of 1O2 became dominant. Implications for dye degrdn. in foods and other consumer products that contain both TiO2 and FD&C Yellow No. 5 as ingredients are discussed.
    15. 15
      Al-Tohamy, R.; Ali, S. S.; Li, F.; Okasha, K. M.; Mahmoud, Y. A. G.; Elsamahy, T.; Jiao, J.; Fu, Y.; Sun, J. A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety. Ecotoxicol. Environ. Saf. 2022, 231, 113160,  DOI: 10.1016/j.ecoenv.2021.113160
      15
      A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety
      Al-Tohamy, Rania; Ali, Sameh S.; Li, Fanghua; Okasha, Kamal M.; Mahmoud, Yehia A.-G.; Elsamahy, Tamer; Jiao, Haixin; Fu, Yinyi; Sun, Jianzhong
      Ecotoxicology and Environmental Safety (2022), 231 (), 113160CODEN: EESADV; ISSN:0147-6513. (Elsevier B.V.)
      A review. The synthetic dyes used in the textile industry pollute a large amt. of water. Textile dyes do not bind tightly to the fabric and are discharged as effluent into the aquatic environment. As a result, the continuous discharge of wastewater from a large no. of textile industries without prior treatment has significant neg. consequences on the environment and human health. Textile dyes contaminate aquatic habitats and have the potential to be toxic to aquatic organisms, which may enter the food chain. This review will discuss the effects of textile dyes on water bodies, aquatic flora, and human health. Textile dyes degrade the esthetic quality of bodies of water by increasing biochem. and COD, impairing photosynthesis, inhibiting plant growth, entering the food chain, providing recalcitrance and bioaccumulation, and potentially promoting toxicity, mutagenicity, and carcinogenicity. Therefore, dye-contg. wastewater should be effectively treated using eco-friendly technologies to avoid neg. effects on the environment, human health, and natural water resources. This review compares the most recent technologies which are commonly used to remove dye from textile wastewater, with a focus on the advantages and drawbacks of these various approaches. This review is expected to spark great interest among the research community who wish to combat the widespread risk of toxic org. pollutants generated by the textile industries.
    16. 16
      Lellis, B.; Fávaro-Polonio, C. Z.; Pamphile, J. A.; Polonio, J. C. Effects of textile dyes on health and the environment and bioremediation potential of living organisms. Biotechnol. Res. Innov. 2019, 3, 275– 290,  DOI: 10.1016/j.biori.2019.09.001
      There is no corresponding record for this reference.
    17. 17
      Ranjan, P.; Singh, R. K.; Suematsu, H.; Phillip, L.; Sarathi, R. Synthesis of nano-ZnO by wire explosion process and its photocatalytic activity. J. Environ. Chem. Eng. 2017, 5, 1676– 1684,  DOI: 10.1016/j.jece.2017.02.036
      17
      Synthesis of nano-ZnO by wire explosion process and its photocatalytic activity
      Ranjan, Prem; Singh, Raj Kamal; Suematsu, H.; Phillip, Ligy; Sarathi, R.
      Journal of Environmental Chemical Engineering (2017), 5 (2), 1676-1684CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
      Zinc oxide (ZnO) nanoparticles were produced by wire explosion process and characterized through X-ray diffraction (XRD) studies and by TEM studies. The particle size anal. indicates that they follow log-normal distribution and the mean size of the ZnO nanoparticles formed is about 44 nm. Optical band gap of ZnO is found to be 3.21 eV by UV-vis diffuse reflectance spectroscopy (DRS). The synthesized ZnO nano particles were used as photo catalyst for degrdn. of methylene blue (MB) in aq. soln. Nano zinc oxide of 100 mg/L was found as the optimum quantity for UV photo degrdn. of 10 mg/L MB. ZnO nanoparticles were verified for its reusability. The results of the study are compared with com. ZnO nanoparticle and with Degussa P-25 TiO2. LC-MS studies were carried out to identify the intermediates and degrdn. pathway.
    18. 18
      Ribeiro, J. P.; Nunes, M. I. Recent trends and developments in Fenton processes for industrial wastewater treatment–A critical review. Environ. Res. 2021, 197, 110957,  DOI: 10.1016/j.envres.2021.110957
      18
      Recent trends and developments in Fenton processes for industrial wastewater treatment - A critical review
      Ribeiro, Joao Peres; Nunes, Maria Isabel
      Environmental Research (2021), 197 (), 110957CODEN: ENVRAL; ISSN:0013-9351. (Elsevier Inc.)
      A review. This study reviews the recent developments in the application of Fenton processes in real industrial wastewater treatment, focusing on heterogeneous catalysts and catalyst regeneration/reuse. This article presents the features, inherent advantages or drawbacks, and primary exptl. results obtained on established and emerging Fenton processes, highlighting the course of innovations and current scenario in a research field that has recently undergone rapid transition. Therefore, a comprehensive literature survey was conducted to review studies published over the last decade dealing with application of Fenton processes to industrial wastewater treatment. The research in this field is primarily focused on discovering or synthesizing new materials to substitute conventional iron salt Fenton catalysts and/or regenerate and reuse the spent catalyst, in contrast to optimizing the application of existing materials. Hence, the emphasis is on producing reusable materials, transitioning from linear to circular economy. Some of the major challenges identified herein include analyzing or improving heterogeneous catalyst lifetime, detg. the predominant pathway of heterogeneous and homogeneous catalysis to pollutant degrdn., and defining the best layout to incorporate Fenton processes into full-scale treatment plants, particularly its coupling with biol. treatment.
    19. 19
      Jing, X.; Yuan, J.; Cai, D.; Li, B.; Hu, D.; Li, J. Concentrating and recycling of high-concentration printing and dyeing wastewater by a disc tube reverse osmosis-Fenton oxidation/low temperature crystallization process. Sep. Purif. Technol. 2021, 266, 118583,  DOI: 10.1016/j.seppur.2021.118583
      19
      Concentrating and recycling of high-concentration printing and dyeing wastewater by a disc tube reverse osmosis-Fenton oxidation/low temperature crystallization process
      Jing, Xinjun; Yuan, Junsheng; Cai, Daniu; Li, Bin; Hu, Dongliang; Li, Jianyang
      Separation and Purification Technology (2021), 266 (), 118583CODEN: SPUTFP; ISSN:1383-5866. (Elsevier B.V.)
      A novel three-step process consisting of disk tube reverse osmosis (DTRO), Fenton oxidn., and low temp. crystn. is described for the treatment of printing and dyeing wastewater. The DTRO step was used to further conc. the wastewater obtained from a nanofiltration (NF) treatment. The desalinated water can be directly reused in the prodn. process, and the COD, TOC, TDS, and SO2-4 concns. of the concd. wastewater were above 1500 mg/L, 500 mg/L, 150 g/L, and 100 g/L, resp. The concd. wastewater was then treated by Fenton oxidn., and the COD, TOC, and chroma removal rates in this step were over 80%, 80%, and nearly 100%, resp. Finally, when the crystn. end point temp. was 0°C, the recovery and purity of the product were above 60% and 99%, resp. For the small amt. of Cl- contained in the cryst. mother liquor, the Cl- and SO2-4 in the mother liquor were sepd. by NF and then sent back to the DTRO step to be re-concd. The degrdn. of org. compds. in wastewater was studied by UV-Vis spectroscopy, three-dimensional fluorescence spectroscopy (3D-EEM), and total org. carbon analyzer. The cryst. products were characterized by X-ray diffraction. The results showed that this new coupling process can realize high reuse of printing and dyeing wastewater.
    20. 20
      Siripireddy, B.; Mandal, B. K. Facile green synthesis of zinc oxide nanoparticles by Eucalyptus globulus and their photocatalytic and antioxidant activity. Adv. Powder Technol. 2017, 28, 785– 797,  DOI: 10.1016/j.apt.2016.11.026
      20
      Facile green synthesis of zinc oxide nanoparticles by Eucalyptus globulus and their photocatalytic and antioxidant activity
      Siripireddy, Balaji; Mandal, Badal Kumar
      Advanced Powder Technology (2017), 28 (3), 785-797CODEN: APTEEE; ISSN:0921-8831. (Elsevier B.V.)
      Eucalyptus globulus leaf ext. mediated synthesis of spherical zinc oxide nanoparticles (ZnO NPs) was carried out under ambient conditions. UV-Visible studies of the synthesized nanoparticles revealed the characteristic peak at 361 nm indicating the formation of ZnO nanoparticles. Powder X-ray Diffractometric (XRD) study showed the strong, intense and narrow-width diffraction peaks indicating the formation of cryst. nanoparticles with most stable hexagonal phase. Field emission-SEM (FE-SEM) and high resoln.-transmission electron microscopic (HR-TEM) results confirmed the formation of spherical ZnO NPs with mean particle size of 11.6 nm which is in close agreement with XRD pattern. Further, energy dispersive X-ray diffraction anal. (EDAX) revealed the formation of highly pure ZnO NPs with the peaks of Zn and O atoms. ZnO NPs exhibited effective photocatalytic activity in degrading Methylene blue and Methyl orange with max. degrdn. efficiency up to 98.3% at 30 mg of catalyst doses. In addn., ZnO NPs exhibited high antioxidant activity against DPPH free radicals scavenger.
    21. 21
      Spada, E. R.; Pereira, E. A.; Montanhera, M. A.; Morais, L. H.; Freitas, R. G.; Costa, R. G.; Soares, F. R.; Ribeiro, C.; de Paula, F. R. Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route. J. Mater. Sci.: Mater. Electron. 2017, 28, 16932– 16938,  DOI: 10.1007/s10854-017-7613-z
      21
      Preparation, characterization and application of phase-pure anatase and rutile TiO2 nanoparticles by new green route
      Spada, Edna R.; Pereira, Eder A.; Montanhera, Maykon A.; Morais, Leonardo H.; Freitas, Renato G.; Costa, Rodrigo G. F.; Soares, Gabriela B.; Ribeiro, Caue; de Paula, Fernando R.
      Journal of Materials Science: Materials in Electronics (2017), 28 (22), 16932-16938CODEN: JSMEEV; ISSN:0957-4522. (Springer)
      Titanium dioxide (TiO2) is used in a range of applications such as photocatalysis and sensor devices. In this work, TiO2 nanoparticles (TiO2NPs) in the crystallog. forms anatase and rutile were prepd. by the green route. The method involves dissolving titanium oxysulfate (TiOSO4) powder in hydrogen peroxide (H2O2) soln. and subsequent thermal treatment of the resultant amorphous ppt. X-ray diffraction (XRD) was used to follow the structural evolution of the amorphous ppt., and microstructure anal. was realized with Rietveld refinement. In addn., the photocatalytic activity of the synthesized TiO2NPs was evaluated by studying the degrdn. of Rhodamine B (RhB) dye. The highest photocatalytic activity was obsd. for TiO2 obtained at 600°C in the crystallog. form anatase.
    22. 22
      Gowri, S.; Rajiv Gandhi, R.; Senthil, S.; Suresh, J.; Sundrarajan, M. Enhancing Antimicrobial Activity of Biotemplated TiO2 Nanoparticles Using Aloe Vera Plant Extract. J. Bionanosci. 2016, 10, 181– 190,  DOI: 10.1166/jbns.2016.1344
      22
      Enhancing antimicrobial activity of biotemplated TiO2 nanoparticles using aloe vera plant extract
      Gowri, S.; Rajiv Gandhi, R.; Senthil, S.; Suresh, J.; Sundrarajan, M.
      Journal of Bionanoscience (2016), 10 (3), 181-190CODEN: JBOIE2; ISSN:1557-7910. (American Scientific Publishers)
      Nowadays, the growth of metal oxide nanoparticles in an eco-friendly manner by plant materials has attracted significant attention. This investigation aims at the synthesis of TiO2 nanoparticles using ext. derived from the Aloe vera plant for the alternative of synthetic pptg. agents, surfactants and solvents like sodium hydroxide, sodium lauryl sulfate and ethanol etc., resp. These biosynthesized metal oxide nanoparticles have a wide range of biol. applications. However, this chapter discusses only on the antimicrobial activities. Addnl., TiO2 nanoparticles were treated on cotton fabric and their efficacy against bacterial and fungal strains were also discussed. This subsequently resulted in powerful antimicrobial activities. The result shows that the coated fabric demonstrated significant antibacterial activity against S. aureus than E. coli due to the attraction of generated active oxygen species of TiO2 with S. aureus. Both samples are produced more potent against C. albicans as well as A. niger fungal strains. The current simple synthetic method aims to provide nanosized materials with well cryst. structure, good optical properties and superior antimicrobial activity using cheap precursor of Aloe vera ext.
    23. 23
      Aravind, M.; Amalanathan, M.; Mary, M. Synthesis of TiO2 nanoparticles by chemical and green synthesis methods and their multifaceted properties. SN Appl. Sci. 2021, 3, 409,  DOI: 10.1007/s42452-021-04281-5
      23
      Synthesis of TiO2 nanoparticles by chemical and green synthesis methods and their multifaceted properties
      Aravind, M.; Amalanathan, M.; Mary, M. Sony Michael
      SN Applied Sciences (2021), 3 (4), 409CODEN: SASNBO; ISSN:2523-3971. (Springer International Publishing AG)
      In this present work, Titanium dioxide nanoparticles (TiO2 NPs) successfully synthesized using the chem. as well as the green synthesis routine. The ethanol provoked the chem. redn. of ions. In the green synthesis, jasmine flower ext. was used as a reducing and stabilizing agent because it contains alkaloids, coumarins, flavonoids. The Rutile phase of TiO2 NPs with an av. cryst. size of 31-42 nm was revealed from the XRD pattern. From the UV-Visible spectroscopy, the optically active region of TiO2 NPs at 385 nm represents the visible region spectrum. The Ti-O-Ti and Ti-O vibration bond formation confirms the formation of TiO2 NPs. The SEM image of TiO2 NPs reveals that the spherical shaped NPs with randomly arranged manner. The obtained results have revealed that the property of TiO2 nanoparticles was similar in both processes. The Photodegrdn. of methylene blue dye was investigated and resulted in the max. degrdn. efficiency of 92% is achieved at 120 min of irradn. The Photodegrdn. study shows the biosynthesized TiO2 NPs exhibits a higher degrdn. efficiency compared to chem. synthesized TiO2 NPs. The antibacterial activity of prepd. TiO2 NP's was studied using grams-pos. and gram-neg. strains. The biol. activities of green synthesized TiO2 NPs are enhanced compared to the chem. synthesized TiO2 NPs. Hence the degrdn. efficiency and zone inhibition layer indicate that the prepd. TiO2 NPs are the potential candidate for environmental and biomedical applications.
    24. 24
      Al-hamoud, K.; Shaik, M. R.; Khan, M.; Alkhathlan, H. Z.; Adil, S. F.; Kuniyil, M.; Assal, M.; Al-Warthan, A.; Siddiqui, M. R. H.; Tahir, M. N.; Khan, S. T.; Mousa, A. A.; Khan, M. Pulicaria undulata Extract-Mediated Eco-Friendly Preparation of TiO2 Nanoparticles for Photocatalytic Degradation of Methylene Blue and Methyl Orange. ACS Omega 2022, 7, 4812– 4820,  DOI: 10.1021/acsomega.1c05090
      24
      Pulicaria undulata Extract-Mediated Eco-Friendly Preparation of TiO2 Nanoparticles for Photocatalytic Degradation of Methylene Blue and Methyl Orange
      Al-hamoud, Khaleel; Shaik, Mohammed Rafi; Khan, Merajuddin; Alkhathlan, Hamad Z.; Adil, Syed Farooq; Kuniyil, Mufsir; Assal, Mohamed E.; Al-Warthan, Abdulrahman; Siddiqui, Mohammed Rafiq H.; Tahir, Muhammad Nawaz; Khan, Shams Tabrez; Mousa, Ahmad Amine; Khan, Mujeeb
      ACS Omega (2022), 7 (6), 4812-4820CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      Eco-friendly approaches for the prepn. of nanomaterials have recently attracted considerable attention of scientific community due to rising environmental distresses. The aim of the current study is to prep. titanium dioxide (TiO2) nanoparticles (NPs) using an eco-friendly approach and investigate their performance for the photocatalytic degrdn. of hazardous org. dyes. For this, TiO2 NPs were prepd. by using the aq. ext. of the Pulicaria undulata (L.) plant in a single step at room temp. Energy-dispersive X-ray spectroscopy established the presence of both titanium and oxygen in the sample. X-ray diffraction revealed the formation of cryst., anatase-phase TiO2 NPs. On the other hand, transmission election microscopy confirmed the formation of spherical shaped NPs. The presence of residual phytomols. as capping/stabilization agents is confirmed by UV-vis anal. and Fourier-transform IR spectroscopy. Indeed, in the presence of P. undulata, the anatase phase of TiO2 is stabilized at a significantly lower temp. (100°C) without using any external stabilizing agent. The green synthesized TiO2 NPs were used to investigate their potential for the photocatalytic degrdn. of hazardous org. dyes including methylene blue and methyl orange under UV-visible light irradn. Due to the small size and high dispersion of NPs, almost complete degrdn. (~ 95%) was achieved in a short period of time (between 1 and 2 h). No significant difference in the photocatalytic activity of the TiO2 NPs was obsd. even after repeated use (three times) of the photocatalyst. Overall, the green synthesized TiO2 NPs exhibited considerable potential for fast and eco-friendly removal of harmful org. dyes.
    25. 25
      Abodif, A. M.; Meng, L.; Ma, S.; Ahmed, A. S.; Belvett, N.; Wei, Z. Z.; Ning, D. Mechanisms and models of adsorption: TiO2-supported biochar for removal of 3, 4-dimethylaniline. ACS Omega 2020, 5, 13630– 13640,  DOI: 10.1021/acsomega.0c00619
      25
      Mechanisms and Models of Adsorption: TiO2-Supported Biochar for Removal of 3,4-Dimethylaniline
      Abodif, Ahmed M.; Meng, Li; MA, Sanjrani; Ahmed, Abdelaal S. A.; Belvett, Norville; Wei, Zhan Zhi; Ning, Du
      ACS Omega (2020), 5 (23), 13630-13640CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      3,4-dimethylaniline (3,4-DMA) was selected as a representative org. aniline compd. A biochar-TiO2 (BC-TiO2) composite was prepd. by sol-gel process to assess its adsorption ability for 3,4-DMA. Simultaneously, the composite adsorption ability and physicochem. properties were examd. Isotherm studies confirmed 3,4-DMA adsorption by BC and BC-TiO2 composite agreed with Langmuir and Toth adsorption models, which meant formation of a 3,4-DMA monolayer on sorbent surfaces. The max. 3,4-DMA adsorption capacity was 322.58 and 285.71 mg/g for BC and BC-TiO2, resp. Adsorption kinetics showed the 3,4-DMA adsorption process on BC and BC-TiO2 composite was controlled by a pseudo-second-order kinetic model with R2 = 0.99.
    26. 26
      Pushpamalini, T.; Keerthana, M.; Sangavi, R.; Nagaraj, A.; Kamaraj, P. Comparative analysis of green synthesis of TiO2 nanoparticles using four different leaf extract. Mater. Today: Proc. 2021, 40, S180– S184,  DOI: 10.1016/j.matpr.2020.08.438
      26
      Comparative analysis of green synthesis of TiO2 nanoparticles using four different leaf extract
      Pushpamalini, T.; Keerthana, M.; Sangavi, R.; Nagaraj, A.; Kamaraj, P.
      Materials Today: Proceedings (2021), 40 (Suppl._1), S180-S184CODEN: MTPAC4; ISSN:2214-7853. (Elsevier Ltd.)
      Green synthesis of nano materials has gained a great attention of current researchers owing to its less toxicity, reproducibility, pollution free, economic and low energy process. Green synthesis of Titanium dioxide (TiO2) nanoparticle was carried out using four different leaf exts. The leaf exts. of Piper betel, Ocimum tenuiflorum, Moringa oleifera, Coriandrum sativum were used as reducing agents to synthesize TiO2 from Titanium tetraisopropoxide. The synthesized TiO2 nanoparticle was then characterized by X-Ray Diffraction (XRD), Fourier Transform-IR Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) and SEM (SEM) techniques. The spectroscopic and microscopic techniques confirmed the formation, size and shape of the TiO2 nano particle. Further the differences in phys. and morphol. characteristics of synthesized nanoparticle incurred with the different with the usage of different leaf ext. was analyzed and justified. The differences in the photocatalytic efficiency of synthesized TiO2 nanoparticles were studied by degrading Malachite green dye. Out of the four dyenanomaterials used, TiO2 synthesized using Moringa oleifera leaf ext. was found to have greater efficiency when compared to other three leaf exts.
    27. 27
      Demir, E.; Creus, A.; Marcos, R. Titanium dioxide and zinc oxide nanoparticles are not mutagenic in the mouse lymphoma assay but modulate the mutagenic effect of UV-C-light post-treatment. Fresen. Environ. Bull. 2017, 26, 1001– 1016
      There is no corresponding record for this reference.
    28. 28
      Gautam, A.; Kshirsagar, A.; Biswas, R.; Banerjee, S.; Khanna, P. K. Photodegradation of organic dyes based on anatase and rutile TiO2 nanoparticles. RSC Adv. 2016, 6, 2746– 2759,  DOI: 10.1039/c5ra20861k
      28
      Photodegradation of organic dyes based on anatase and rutile TiO2 nanoparticles
      Gautam, Ashish; Kshirsagar, Anuraj; Biswas, Rahul; Banerjee, Shaibal; Khanna, Pawan K.
      RSC Advances (2016), 6 (4), 2746-2759CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      The present work highlights a simple nanochem. based clean and efficient process for effective degrdn. of various org. dyes by use of anatase and rutile TiO2 nanoparticles. Based on photodegrdn. studies it was obsd. that at certain exptl. parameters, rutile TiO2 was as effective as anatase for the degrdn. of indigo carmine (IC) dye in aq. soln. However, anatase TiO2 was found to be much more efficient against methylene blue (MB), methyl orange (MO), rhodamine B (RB) and eriochrome black T (EBT) under short UV irradn. The photodegrdn. study of these org. dyes was also performed under long UV irradn. employing both anatase and rutile titania and the results showed similar trends. However, only EBT photodegrdn. indicated equal photocatalytic activity by both phases. The catalytic degrdn. of the org. dyes was studied by degrdn. kinetics. The max. degrdn. efficiency using anatase and rutile titania photocatalysts was found to be 88% and 77% in the case of MB under short UV irradn. while about 65% was found in the case of EBT under long UV irradn. The reuse of photocatalyst even after five cycles retained the degrdn. efficiency of 83% and 71% resp. for anatase and rutile when tested against MB.
    29. 29
      Dodoo-Arhin, D.; Buabeng, F. P.; Mwabora, J. M.; Amaniampong, P. N.; Agbe, H.; Nyankson, E.; Obada, D. O.; Asiedu, N. Y. The effect of titanium dioxide synthesis technique and its photocatalytic degradation of organic dye pollutants. Heliyon 2018, 4, e00681  DOI: 10.1016/j.heliyon.2018.e00681
      There is no corresponding record for this reference.
    30. 30
      Diallo, A.; Manikandan, E.; Rajendran, V.; Maaza, M. Physical & enhanced photocatalytic properties of green synthesized SnO2 nanoparticles via Aspalathus linearis. J. Alloys Compd. 2016, 681, 561– 570,  DOI: 10.1016/j.jallcom.2016.04.200
      30
      Physical & enhanced photocatalytic properties of green synthesized SnO2 nanoparticles via Aspalathus linearis
      Diallo, A.; Manikandan, E.; Rajendran, V.; Maaza, M.
      Journal of Alloys and Compounds (2016), 681 (), 561-570CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      This contribution reports on the synthesis and the main phys. properties of n-type SnO2 nanoparticles synthesized for the first time by a completely green chem. process using Aspalathus linearis's natural ext. as an effective chelating agent. Their surface/interface and vol. properties by X-rays diffraction, Raman, X-rays photoemission and photoluminescence spectroscopies are reported. Their av. diam. ranging from 2.1 to 19.3 nm follows a thermal governed equation of 〈Oparticles〉 = 1.048 10-5 T2 - 4.92 10-3 T + 2.84. The smallest SnO2 nanoparticles exhibit effective photocatalytic responses to Methylene blue, Congo red and Eosin Y.
    31. 31
      Nea, D.; Kondamareddy, K. K.; Bin, H.; Lu, D.; Kumar, P.; Dwivedi, R. K.; Pelenovich, D.; Zhao, X.-Z.; Gao, W.; Fu, D. Enhanced visible light photodegradation activity of RhB/METHYLENE BLUE from aqueous solution using nanosized novel Fe-Cd co-modified ZnO. Sci. Rep. 2018, 8, 10691,  DOI: 10.1038/s41598-018-29025-1
      There is no corresponding record for this reference.
    32. 32
      Tammina, S. K.; Mandal, B. K.; Kadiyala, N. K. Photocatalytic Degradation of Methylene Blue Dye by Nonconventional synthesized SnO2 Nanoparticles. Environ. Nanotechnol. Monit. Manag. 2018, 10, 339– 350,  DOI: 10.1016/j.enmm.2018.07.006
      There is no corresponding record for this reference.
    33. 33
      Arunkumar, S.; Alagiri, M. Synthesis and Characterization of Spindle-Like TiO2 Nanostructures and Photocatalytic Activity on Methyl Orange and Methyl Blue Dyes Under Sunlight Radiation. J. Cluster Sci. 2017, 28, 2635– 2643,  DOI: 10.1007/s10876-017-1245-6
      33
      Synthesis and Characterization of Spindle-Like TiO2 Nanostructures and Photocatalytic Activity on Methyl Orange and Methyl Blue Dyes Under Sunlight Radiation
      Arunkumar, S.; Alagiri, M.
      Journal of Cluster Science (2017), 28 (5), 2635-2643CODEN: JCSCEB; ISSN:1040-7278. (Springer)
      Spindle-like TiO2 nanostructures was prepd. by a simple one pot solvothermal method followed by calcination at 400°C for 3 h. The sample was characterized using various techniques such as X-ray diffractometer, transmission electron microscopy, Fourier transform IR spectroscopy and UV-Vis absorption spectroscopy. The crystal structure of TiO2 nanostructure was measured by X-ray diffractometer. According to the XRD result, the peaks in the sample can be indexed to anatase phase of TiO2. The morphol. characterization of TiO2 sample was examd. by transmission electron microscopy. The synthesized sample consisted of spindle-like shape with size in the range of 50-70 nm. The band gap value of Spindle-like TiO2 nanostructures is 2.92 eV, which is lower than that of bulk TiO2 of 3.2 eV. The FTIR bands obsd. at 493, 443 and 428 cm-1 confirms the presence of TiO2. The Spindle-like TiO2 nanostructures showed photodegrdn. ability for methyl orange and methyl blue dye. The reuse evaluation of the Spindle-like TiO2 nanostructures showed that their photocatalytic activity had good durability.
    34. 34
      Santhi, K.; Rani, C.; Karuppuchamy, S. Synthesis and characterization of a novel SnO/SnO2 hybrid photocatalyst. J. Alloys Compd. 2016, 662, 102– 107,  DOI: 10.1016/j.jallcom.2015.12.007
      34
      Synthesis and characterization of a novel SnO/SnO2 hybrid photocatalyst
      Santhi, K.; Rani, C.; Karuppuchamy, S.
      Journal of Alloys and Compounds (2016), 662 (), 102-107CODEN: JALCEU; ISSN:0925-8388. (Elsevier B.V.)
      Nanostructured SnO/SnO2 hybrid material was successfully synthesized by microwave irradn. method. X-ray diffraction spectroscopy shows the formation of SnO/SnO2 nanocomposite material. Nanosphere morphol. of the nanocomposite was obsd. by SEM. UV-visible diffuse reflectance spectra demonstrate that the light absorption capacity of SnO/SnO2 nanocomposite was extended to the visible region. The photocatalytic activity of SnO/SnO2 nanocomposite was investigated by the degrdn. of Methylene blue under UV light irradn. The effect of SnO/SnO2 nanocomposite dose, dye concn., pH and irradn. time for photodegrdn. of Methylene blue dye was also studied. SnO/SnO2 nanocomposite exhibits higher photocatalytic activity in neutral pH.
    35. 35
      Mageshwari, K.; Sathyamoorthy, R.; Park, J. Photocatalytic activity of hierarchical CuO microspheres synthesized by facile reflux condensation method. Powder Technol. 2015, 278, 150– 156,  DOI: 10.1016/j.powtec.2015.03.004
      35
      Photocatalytic activity of hierarchical CuO microspheres synthesized by facile reflux condensation method
      Mageshwari, K.; Sathyamoorthy, R.; Park, Jinsub
      Powder Technology (2015), 278 (), 150-156CODEN: POTEBX; ISSN:0032-5910. (Elsevier B.V.)
      Flower-shaped hierarchical CuO microspheres consisting of interpenetrating nanosheets were successfully synthesized by reflux condensation method without using any surfactant or templates. X-ray diffraction revealed the formation of single phase CuO exhibiting monoclinic crystal structure. SEM and transmission electron microscopy confirmed the formation of hierarchical flower-shaped CuO microspheres made up of nanosheets as building blocks. UV-vis diffused reflectance spectroscopy showed a steep absorption between 700 and 950 nm, and the corresponding band gap of CuO nanoparticles was found to be 1.59 eV. To explore the potential capability of flower-shaped CuO microspheres for wastewater treatment, the photocatalytic activity of CuO nanostructures was evaluated by monitoring the photodegrdn. of methyl orange (MO) and methylene blue (MB) dyes in the presence of hydrogen peroxide under UV light irradn. Exptl. results demonstrated that CuO hierarchical architecture possesses good photocatalytic activity towards MO and MB dyes, indicating the feasibility of using CuO for the effective removal of org. contaminants from wastewater.
    36. 36
      Yousefi, R.; Jamali-Sheini, F.; Cheraghizade, M.; Khosravi-Gandomani, S.; Sáaedi, A.; Huang, N. M.; Basirun, M.; Azarang, M. Enhanced visible-light photocatalytic activity of strontium-doped zinc oxide nanoparticles. Mater. Sci. Semicond. Process. 2015, 32, 152– 159,  DOI: 10.1016/j.mssp.2015.01.013
      36
      Enhanced visible-light photocatalytic activity of strontium-doped zinc oxide nanoparticles
      Yousefi, Ramin; Jamali-Sheini, Farid; Cheraghizade, Mohsen; Khosravi-Gandomani, Sara; Saaedi, Abdolhossein; Huang, Nay Ming; Basirun, Wan Jefrey; Azarang, Majid
      Materials Science in Semiconductor Processing (2015), 32 (), 152-159CODEN: MSSPFQ; ISSN:1369-8001. (Elsevier Ltd.)
      Strontium-doped zinc oxide nanoparticles (Zn1-xSrxO NPs; x=0, 0.02, 0.04, and 0.06) were synthesized by a sol-gel method. Transmission electron microscopy (TEM) and SEM (SEM) images showed NPs with nearly spherical shapes, with sizes from 27 to 41 nm for high Sr concn. and undoped ZnO NPs, resp. X-ray diffraction (XRD) patterns, selected area electron diffraction (SAED) patterns, and Raman spectra indicated that the undoped and Sr-doped ZnO NPs were crystd. in a hexagonal wurtzite structure. However, the Raman results revealed a decrease in the cryst. quality with an increase in the Sr concn. in the ZnO structure. Evidence of dopant incorporation is demonstrated by XPS of the Sr-doped ZnO NPs. From the results of optical characterizations, the band-gap values of the Zn0.98Sr0.02O and Zn0.96Sr0.04O NPs decreased, while the band-gap value of the Zn0.94Sr0.06O NPs increased in comparison to the band-gap value of the undoped ZnO NPs. Finally, the obtained NPs were used as a photocatalyst to remove methylene blue (MB). Observations showed that the efficiency of the photocatalyst activity of the ZnO NPs was significantly increased by increasing the Sr, but until an optimum concn.
    37. 37
      Azarang, M.; Shuhaimi, A.; Yousefi, R.; Jahromi, S. P. One-pot sol–gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of Methylene Blue. RSC Adv. 2015, 5, 21888– 21896,  DOI: 10.1039/c4ra16767h
      37
      One-pot sol-gel synthesis of reduced graphene oxide uniformly decorated zinc oxide nanoparticles in starch environment for highly efficient photodegradation of Methylene Blue
      Azarang, Majid; Shuhaimi, Ahmad; Yousefi, Ramin; Jahromi, Siamak Pilban
      RSC Advances (2015), 5 (28), 21888-21896CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      ZnO NPs + reduced graphene oxide (rGO) nanocomposites were synthesized using a sol-gel method with starch as the polymn. agent. Long-chain starch compds. were used to terminate the growth of the ZnO NPs on rGO and stabilize them. The resulting products were annealed at 350 °C to remove the starch and produce a reduced graphene oxide (rGO) sheet in one-pot without any post-annealing processes. Microscopic studies showed that the NPs were dispersed on the rGO sheet. They had a spherical shape and a size of approx. 25 ± 10 nm. In addn., these studies revealed that the NPs were single crystals. The X-ray diffraction pattern of the NPs indicated a hexagonal (wurtzite) structure. The results of Fourier transform IR spectrum anal. (FTIR) revealed that the GO sheet was transformed into rGO via the sol-gel method in the starch environment. The results of photoluminescence spectroscopy demonstrated that the incorporation of reduced graphene oxide (rGO) sheets with ZnO NPs suppressed the electron-hole recombination of the composite. Therefore, a significant enhancement in the photocatalytic degrdn. of methylene blue (MB) was obsd. with the ZnO NPs + rGO nanocomposite compared to the bare ZnO nanoparticles.
    38. 38
      Mekewi, M. A.; Darwish, A. S.; Amin, M. S.; Eshaq, G.; Bourazan, H. A. Copper nanoparticles supported onto montmorillonite clays as efficient catalyst for methylene blue dye degradation. Egypt. J. Pet. 2016, 25, 269– 279,  DOI: 10.1016/j.ejpe.2015.06.011
      There is no corresponding record for this reference.
    39. 39
      Pascariu, P.; Airinei, A.; Olaru, N.; Olaru, L.; Nica, V. Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers. Ceram. Int. 2016, 42, 6775– 6781,  DOI: 10.1016/j.ceramint.2016.01.054
      39
      Photocatalytic degradation of Rhodamine B dye using ZnO-SnO2 electrospun ceramic nanofibers
      Pascariu, Petronela; Airinei, Anton; Olaru, Niculae; Olaru, Liliana; Nica, Valentin
      Ceramics International (2016), 42 (6), 6775-6781CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
      ZnO-SnO2 nanofibers were fabricated by the electrospinning technique combined with calcination at 600 °C. Their structural and morphol. properties were analyzed by X-ray diffraction and scanning/transmission electron microscopy, and their photocatalytic activity was investigated by the degrdn. of Rhodamine B (RhB) dye by visible light irradn. UV-vis spectral data were used to est. the photodegrdn. efficiency of the metal oxide nanocomposites. All the RhB dye samples were tested for six hours of degrdn. the highest efficiency being obtained for a molar ratio Sn/Zn of 0.030.
    40. 40
      Wang, L.; Zhou, Q.; Zhang, G.; Liang, Y.; Wang, B.; Zhang, W.; Lei, W.; Wang, W. A facile room temperature solution-phase route to synthesize CuO nanowires with enhanced photocatalytic performance. Mater. Lett. 2012, 74, 217– 219,  DOI: 10.1016/j.matlet.2012.01.123
      40
      A facile room temperature solution-phase route to synthesize CuO nanowires with enhanced photocatalytic performance
      Wang, Lijuan; Zhou, Qing; Zhang, Guling; Liang, Yujie; Wang, Baoshun; Zhang, Weiwei; Lei, Bo; Wang, Wenzhong
      Materials Letters (2012), 74 (), 217-219CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      CuO nanowires have been prepd. with high yield at low cost by a facile room temp. soln. phase route. The compn., morphol. and size of the as-prepd. CuO nanowires were characterized by powder X-ray diffraction (XRD), SEM, and transmission electron microscopy (TEM). The UV-vis absorption spectra demonstrate that the as-prepd. CuO nanowires exhibit quantum size confinement effects. The photocatalytic properties of CuO nanowires were further investigated by evaluating on photo-degrdn. of a simulation, physicochem. pollutant rhodamine B (RhB). The exptl. results indicated that CuO nanowires have enhanced photocatalytic performance with 95.5% decompn. of RhB after 9 h reaction under UV light irradn., which was much higher than that of com. CuO powders (39.6%).
    41. 41
      Shekofteh-Gohari, M.; Habibi-Yangjeh, A. Fabrication of novel magnetically separable visible-light-driven photocatalysts through photosensitization of Fe3O4/ZnO with CuWO4. J. Ind. Eng. Chem. 2016, 44, 174– 184,  DOI: 10.1016/j.jiec.2016.08.028
      41
      Fabrication of novel magnetically separable visible-light-driven photocatalysts through photosensitization of Fe3O4/ZnO with CuWO4
      Shekofteh-Gohari, Maryam; Habibi-Yangjeh, Aziz
      Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2016), 44 (), 174-184CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
      In this work, we have successfully fabricated ternary Fe3O4/ZnO/CuWO4 nanocomposites with different wt. percentages of CuWO4 by refluxing method. The visible-light photocatalytic activity of the Fe3O4/ZnO/CuWO4 nanocomposites was investigated using Rhodamine B. It was found that the photocatalytic activity of the nanocomposites significantly depends on the wt. percentage of CuWO4. Among the prepd. samples, the nanocomposite with 40% of CuWO4 displayed the highest activity. The superior photocatalytic ability of the Fe3O4/ZnO/CuWO4 (40%) nanocomposite compared to the binary Fe3O4/ZnO and Fe3O4/CuWO4 photocatalysts in degrdn. of methylene blue, as another org. dye, under visible-light irradn. was also confirmed.
    42. 42
      Tadjarodi, A.; Akhavan, O.; Bijanzad, K. Photocatalytic activity of CuO nanoparticles incorporated in mesoporous structure prepared from bis (2-aminonicotinato) copper (II) microflakes. Trans. Nonferrous Met. Soc. China 2015, 25, 3634– 3642,  DOI: 10.1016/s1003-6326(15)64004-3
      42
      Photocatalytic activity of CuO nanoparticles incorporated in mesoporous structure prepared from bis(2-aminonicotinato) copper(II) microflakes
      Tadjarodi, Azadeh; Akhavan, Omid; Bijanzad, Keyvan
      Transactions of Nonferrous Metals Society of China (2015), 25 (11), 3634-3642CODEN: TNMCEW; ISSN:1003-6326. (Elsevier B.V.)
      An easy method for prepg. CuO nanoparticles incorporated in a mesoporous structure was presented based on the thermal decompn. of a copper complex. The novel copper coordination compd. of [Cu(anic)2]·0.75H2O (anic= 2-aminonicotinate) with the microflake morphol. was synthesized through the reaction of 2-aminonicotinic acid (Hanic) and copper(II) nitrate. Using elemental anal. and Fourier transform IR (FTIR) spectroscopy, the chem. compn. of CuC12H11.5N4O4.75 was proposed. Calcination process at 550 °C for 4 h transformed the microflakes into CuO nanoparticles incorporated in a mesoporous structure. The FTIR peaks assigned to 2-aminonicotinate were completely removed after calcination, confirming CuO formation. X-ray diffraction (XRD) anal. also confirmed the generation of pure and cryst. CuO. SEM showed CuO nanoparticles with the av. diam. of 75 nm. The diffuse reflectance spectrum (DRS) of the CuO nanoparticles showed a band gap energy of -1.58 eV. The degrdn. efficiency toward rhodamine B was almost 100 % after 5 h illumination when both CuO and H2O2 were utilized. The results show that the product can be used as an efficient photocatalyst for water treatment.
    43. 43
      Fu, L.; Zheng, Y.; Ren, Q.; Wang, A.; Deng, B. Green biosynthesis of SnO2 nanoparticles by plectranthus amboinicus leaf extract their photocatalytic activity toward rhodamine B degradation. J. Ovonic Res. 2015, 11, 21– 26
      43
      Green biosynthesis of SnO2 nanoparticles by plectranthus amboinicus leaf extract their photocatalytic activity toward rhodamine b degradation
      Fu, L.; Zheng, Y.; Ren, Q.; Wang, A.; Deng, B.
      Journal of Ovonic Research (2015), 11 (1), 21-26CODEN: JOROAK; ISSN:1584-9953. (National Institute of Materials Physics)
      In this paper, we report the first time prepn. of SnO2 nanoparticles (NPs) using a green chem. method. The leaf ext. of Plectranthus amboinicus was used as reducing and stabilization agent for synthesizing SnO2 NPs. The synthesized SnO2 NPs were characterized by SEM, EDX, XRD and UV-vis spectroscopy. Results showed that the biosynthesized SnO2 NPs owing a high purity. The photocatalytic property of the biosynthesized SnO2 NPs was investigated by photodegrdn. of rhodamine B (Rh B) under visible light illumination. Results indicated that the photocatalytic performance of the biosynthesized SnO2 NPs is much higher than that of com. SnO2. Moreover, the biosynthesized SnO2 also exhibited an excellent reusability.
    44. 44
      Rahman, Q. I.; Ahmad, M.; Misra, S. K.; Lohani, M. Effective photocatalytic degradation of rhodamine B dye by ZnO nanoparticles. Mater. Lett. 2013, 91, 170– 174,  DOI: 10.1016/j.matlet.2012.09.044
      44
      Effective photocatalytic degradation of Rhodamine B dye by ZnO nanoparticles
      Rahman, Qazi Inamur; Ahmad, Musheer; Misra, Sunil Kumar; Lohani, Minaxi
      Materials Letters (2013), 91 (), 170-174CODEN: MLETDJ; ISSN:0167-577X. (Elsevier B.V.)
      Highly cryst. ZnO nanoparticles (NPs) were synthesized with Zn acetate as precursor and oxalic acid at 80° C through the simple soln. phase approach. The synthesized ZnO NPs possessed monodispersity with the av. size 20-30 nm. The cryst. properties revealed the typical hexagonal wurtzite phase with orientation along c-axis. The photocatalytic activity investigation was carried out by performing the decompn. of Rhodamine-B dye under UV illumination over as-synthesized ZnO NPs. The Rhodamine B dye considerably degraded by ∼95% within 70 min in the presence of as-synthesized ZnO NPs. An excellent rate const. (k = 0.0343 min-1) was obtained for the degrdn. of Rhodamine B dye.
    45. 45
      Soltani, N.; Saion, E.; Hussein, M. Z.; Erfani, M.; Abedini, A.; Bahmanrokh, G.; Navasery, P.; Vaziri, P. Visible light-induced degradation of methylene blue in the presence of photocatalytic ZnS and CdS nanoparticles. Int. J. Mol. Sci. 2012, 13, 12242– 12258,  DOI: 10.3390/ijms131012242
      45
      Visible light-induced degradation of methylene blue in the presence of photocatalytic ZnS and CdS nanoparticles
      Soltani, Nayereh; Saion, Elias; Hussein, Mohd. Zobir; Erfani, Maryam; Abedini, Alam; Bahmanrokh, Ghazaleh; Navasery, Manizheh; Vaziri, Parisa
      International Journal of Molecular Sciences (2012), 13 (), 12242-12258CODEN: IJMCFK; ISSN:1422-0067. (MDPI AG)
      ZnS and CdS nanoparticles were prepd. by a simple microwave irradn. method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal cryst. structures, resp. The band gap energies of ZnS and CdS nanoparticles were estd. using UV-visible absorption spectra to be about 4.22 and 2.64 eV, resp. Photocatalytic degrdn. of methylene blue was carried out using phys. mixts. of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradn. The residual concn. of methylene blue soln. was monitored using UV-visible absorption spectrometry. From the study of the variation in compn. of ZnS:CdS, a compn. of 1:4 (by wt.) was found to be very efficient for degrdn. of methylene blue. In this case the degrdn. efficiency of the photocatalyst nanoparticles after 6 h irradn. time was about 73% with a reaction rate of 3.61 × 10-3 min-1. Higher degrdn. efficiency and reaction rate were achieved by increasing the amt. of photocatalyst and initial pH of the soln.
    46. 46
      Chen, X.; Wu, Z.; Liu, D.; Gao, Z. Preparation of ZnO photocatalyst for the efficient and rapid photocatalytic degradation of azo dyes. Nanoscale Res. Lett. 2017, 12, 143,  DOI: 10.1186/s11671-017-1904-4
      46
      Preparation of ZnO Photocatalyst for the Efficient and Rapid Photocatalytic Degradation of Azo Dyes
      Chen Xiaoqing; Wu Zhansheng; Liu Dandan; Gao Zhenzhen
      Nanoscale research letters (2017), 12 (1), 143 ISSN:1931-7573.
      Zinc oxide (ZnO) photocatalysts were synthesized by sol-gel method using zinc acetate as precursor for degradation of azo dyes under UV irradiation. The resultant samples were characterized by different techniques, such as XRD, SEM, and EDX. The influence of preparation conditions such as calcination temperature and composite ratio on the degradation of methyl orange (MO) was investigated. ZnO prepared with a composite ratio of 4:1 and calcination temperature of 400 °C exhibited 99.70% removal rate for MO. The effect of operation parameters on the degradation was also studied. Results showed that the removal rate of azo dyes increased with the increased dosage of catalyst and decreased initial concentration of azo dyes and the acidic condition is favorable for degradation. Furthermore, the kinetics and scavengers of the reactive species during the degradation were also investigated. It was found that the degradation of azo dyes fitted the first-order kinetics and superoxide ions were the main species. The proposed photocatalyst can efficiently and rapidly degrade azo dyes; thus, this economical and environment-friendly photocatalyst can be applied to the treatment of wastewater contaminated with synthetic dyes.
    47. 47
      Vidya, C.; Manjunatha, C.; Chandraprabha, M. N.; Rajshekar, M.; Raj, A. R. Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications. J. Environ. Chem. Eng. 2017, 5, 3172– 3180,  DOI: 10.1016/j.jece.2017.05.058
      47
      Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications
      Vidya., C.; Manjunatha., C.; Chandraprabha., M. N.; Rajshekar, Megha; Raj. M. A. L, Antony
      Journal of Environmental Chemical Engineering (2017), 5 (4), 3172-3180CODEN: JECEBG; ISSN:2213-3437. (Elsevier Ltd.)
      The present study describes the use Artocarpus Heterophyllus leaves ext. for the synthesis of Zinc oxide nanoparticles (ZnO NPs). The particles were calcined at 400, 600 and 800°C for 1 h. Powder X-Ray Diffraction (PXRD) results showed the ZnO NPs calcined at different temp. to be cryst. with hexagonal wurtzite phase. The morphol. was studied using SEM (SEM) and elemental compn. investigated using energy dispersive spectroscopy (EDS) showed peaks for Zn and O only. The exact size of ZnO particles and its cryst. nature were investigated from transmission electron microscopy (TEM),High resoln. transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The TEM showed the size range of the ZnO NPs to be ∼10-15 nm at 400°C, ∼15-25 nm at 600°C and ∼25-30 at 800°C which are in good agreement with the SEM observation. The band gap energy was calcd. from UV diffuse reflectance spectra and found to be 3.42, 3.38 and 3.35 eV for 400, 600 and 800°C resp. The fourier transform infra-red spectroscopy (FTIR) spectra of leaf ext. confirmed the presence of phyto constituents such as amines, amides, quinines and ketones in the leaf ext. The ZnO NPs calcined at 400°C having higher band gap energy and smaller size was used for photocatalytic degrdn. The studies showed the efficiency greater than 90% towards degrdn. of 20 ppm Congo red dye soln. at 0.24 g/L ZnO NPs in 1 h at pH 9.
    48. 48
      Zangeneh, H.; Zinatizadeh, A. A. L.; Habibi, M.; Akia, M.; Hasnain Isa, M. H. Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review. J. Ind. Eng. Chem. 2015, 26, 1– 36,  DOI: 10.1016/j.jiec.2014.10.043
      48
      Photocatalytic oxidation of organic dyes and pollutants in wastewater using different modified titanium dioxides: A comparative review
      Zangeneh, H.; Zinatizadeh, A. A. L.; Habibi, M.; Akia, M.; Hasnain Isa, M.
      Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2015), 26 (), 1-36CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
      This article compares the effectiveness of pure and modified TiO2 for photocatalytic degrdn. of different org. matters and clarifies the advantages of the modified TiO2 with photoactivity under visible light. Photocatalytic degrdn. technique with titanium dioxide is generally applied for treating wastewater contg. refractory org. contaminants with the purpose of reuse due to its ability to achieve complete mineralization of the compds. under mild conditions such as ambient temp. and pressure. Performance of different types of photocatalytic reactors, effects of important parameters on the reactors performance, effect of various methods used to enhance the photocatalytic activity of TiO2 including doping, sensitization of TiO2 and surface modification are discussed in details. So far, a few review papers have been published and extensive information have been reported on the structure and electronic properties of TiO2, difference between TiO2 with other common semiconductors used for photocatalytic applications, various methods used to enhance the photocatalytic characteristics of TiO2 including dye sensitization, doping, coupling, the effects of various operating parameters on the photocatalytic degrdn. of phenols and dyes and types of reactors, comparison between effective modes of TiO2 application as immobilized on surface or as suspension, and photocatalytic hybrid membrane system are presented. However, in the published review papers, performance of the different modified photocatalysts is rarely compared quant. Therefore, in order to provide an inclusive and effective comparison among the studies, specific removal rate (SRR) (mg compd.removed/g cat. h) was calcd. as a response.
    49. 49
      Ban, J. J.; Xu, G. C.; Zhang, L.; Lin, H.; Sun, Z. P.; Lv, Y.; Jia, D. Z. Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes. J. Solid State Chem. 2017, 256, 151– 157,  DOI: 10.1016/j.jssc.2017.09.002
      49
      Mesoporous ZnO microcube derived from a metal-organic framework as photocatalyst for the degradation of organic dyes
      Ban, Jin-jin; Xu, Guan-cheng; Zhang, Li; Lin, He; Sun, Zhi-peng; Lv, Yan; Jia, Dian-zeng
      Journal of Solid State Chemistry (2017), 256 (), 151-157CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
      A cube-like porous ZnO architecture was synthesized by direct two-step thermolysis of a zinc-based metal-org. framework [(CH3)2NH2][Zn(HCOO)3]. The obtained ZnO microcube was characterized by powder X-ray diffraction, SEM, transmission electron microscopy and nitrogen adsorption and desorption isotherms. The mesoporous ZnO microcube was comprised by many nanoparticles, and inherited the cube shape from [(CH3)2NH2][Zn(HCOO)3] precursor. With large surface area and mesoporous structure, the ZnO microcube exhibits excellent photocatalytic activities against methyl orange (MO) and rhodamine B (RhB) under UV irradn., and the degrdn. rates reached 99.7% and 98.1% within 120 min, resp.

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    • Reusability and stability investigation of TDO NPs and GC-MS analysis of phyto-chemicals (PDF)


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