ACS Publications. Most Trusted. Most Cited. Most Read
Acidity of Carboxylic Acid Ligands Influences the Formation of VO2(A) and VO2(B) Nanocrystals under Solvothermal Conditions
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Nanosci. Au 2023, 3, 5, 381-388
  • Open Access
Article

Acidity of Carboxylic Acid Ligands Influences the Formation of VO2(A) and VO2(B) Nanocrystals under Solvothermal Conditions
Click to copy article linkArticle link copied!

Open PDFSupporting Information (3)

ACS Nanoscience Au

Cite this: ACS Nanosci. Au 2023, 3, 5, 381–388
Click to copy citationCitation copied!
https://doi.org/10.1021/acsnanoscienceau.3c00014
Published June 22, 2023

Copyright © 2023 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Vanadium dioxide (VO2) can adopt many different crystal structures at ambient temperature and pressure, each with different, and often desirable, electronic, optical, and chemical properties. Understanding how to control which crystal phase forms under various reaction conditions is therefore crucial to developing VO2 for various applications. This paper describes the impact of ligand acidity on the formation of VO2 nanocrystals from the solvothermal reaction of vanadyl acetylacetonate (VO(acac)2) with stoichiometric amounts of water. Carboxylic acids examined herein favor the formation of the monoclinic VO2(B) phase over the tetragonal VO2(A) phase as the concentration of water in the reaction increases. However, the threshold concentration of water required to obtain phase-pure VO2(B) nanocrystals increases as the pKa of the carboxylic acid decreases. We also observe that increasing the concentration of VO(acac)2 or the concentration of acid while keeping the concentration of water constant favors the formation of VO2(A). Single-crystal electron diffraction measurements enable the identification of vanadyl carboxylate species formed in reactions that do not contain enough water to promote the formation of VO2. Increasing the length of the carbon chain on aliphatic carboxylic acids did not impact the phase of VO2 nanocrystals obtained but did result in a change from nanorod to nanoplatelet morphology. These results suggest that inhibiting the rate of hydrolysis of the VO(acac)2 precursor either by decreasing the ratio of water to VO(acac)2 or by increasing the fraction of water molecules that are protonated favors the formation of VO2(A) over VO2(B).

This publication is licensed under

CC-BY 4.0 .
  • cc licence
  • by licence
Copyright © 2023 The Authors. Published by American Chemical Society

Subjects

what are subjects

Keywords

what are keywords

Introduction

Click to copy section linkSection link copied!
Vanadium dioxide (VO2) has attracted significant attention because it exhibits multiple crystal phases, all with different properties and uses. The most stable bulk phase, VO2(R), with a rutile structure, is well known for its low-temperature metal-to-insulator transition to VO2(M) and is used for smart window applications. (1,2) Like VO2(M), the metastable tetragonal phase known as VO2(A) has also been investigated as a material for optical switches, (3,4) while the metastable monoclinic phase known as VO2(B) has been used as a cathode material in lithium- and sodium-ion batteries. (5−11) All of these applications benefit from the solution processability afforded by nanocrystalline morphologies. Given the variation in the application of multiple crystal polymorphs of VO2, there is considerable motivation to understand how to control which polymorphs form under various reaction conditions.
Nanocrystals of the metastable polymorphs VO2(A) and VO2(B) are typically synthesized using solvothermal methods at elevated pressure. (6,8−10,12−18) These methods often utilize V2O5 and a reductant in water, and control over the crystal phase is usually achieved by varying the reaction temperature. VO2(A) is the major product obtained at reaction temperatures between 220 and 270 °C, and VO2(B) is the major product obtained at temperatures between 180 and 200 °C. (6,8−10,12−15) Varying the pressure by varying the volume of the reaction mixture within the pressure-sealed reaction vessel (19) also impacts the phase of the resulting product. One study showed that a mixture containing V2O5 and oxalic acid reacting at 180 °C in a pressure-sealed autoclave could result in phase-pure VO2(B) after 24 h and phase-pure VO2(A) after 7 days. (20) However, this result could only be obtained with a filling ratio of 80/100 mL in the pressure-sealed vessel: a filling ratio of 60/100 mL only yielded VO2(B) with no phase change present after 7 days.
Recently, we demonstrated that tuning the chemical rather than physical reaction conditions enables control over the crystal phase of VO2 nanocrystals. Specifically, we showed that decreasing the concentration of water present in the solvothermal reaction mixture of vanadyl acetylacetonate (VO(acac)2) and lauric acid in toluene to 4 equiv or less per vanadium center produces phase-pure VO2(A) nanocrystals, whereas using 20 equiv or more of water produces phase-pure VO2(B) nanocrystals. (21) This approach has the added advantage of enabling access to smaller nanocrystals with dimensions less than 500 nm. In contrast, reactions that use water as the solvent produce very large particles, usually nanorods that are several microns long. (6,9,10) We hypothesize that the mechanism by which the concentration of water impacts the crystal phase of VO2 nanocrystals is through controlling the relative rates of precursor hydrolysis and condensation. Decreasing the concentration of water slows hydrolysis and may allow nanocrystal nucleation via condensation of partially hydrolyzed species. We suspect that condensation of these partially hydrolyzed species favors the formation of VO2(A) over VO2(B).
Here, we test this hypothesis by tuning the pKa and steric bulk of organic carboxylic acid ligands to vary the rate of precursor hydrolysis. We find that replacing lauric acid with a stronger acid, namely trifluoroacetic acid, expands the range of water concentrations that lead to the formation of VO2(A) nanocrystals by a factor of almost four, up to 15 equiv of water per vanadium center. Increasing the concentration of trifluoroacetic acid and/or the VO(acac)2 precursor relative to water also favors the formation of VO2(A) over VO2(B). These experiments indicate that reaction conditions that suppress the rate of precursor hydrolysis (i.e., decreasing the water concentration or increasing the acidity of the reaction mixture) favor the formation of VO2(A). (21) In contrast to varying the acidity of carboxylic acid, changing the chain length of aliphatic carboxylic acids does not alter the crystal phase of the product. This observation indicates that the steric bulk of these ligands does not alter the relative rates of precursor hydrolysis and condensation significantly enough to impact which crystal phase of VO2 nucleates.

Results and Discussion

Click to copy section linkSection link copied!
We set out to investigate the role of carboxylic acid ligands in the synthesis of VO2 nanocrystals from VO(acac)2. We varied two properties of these ligands─their acidity and their steric bulk─to determine which property has the largest influence on the resulting nanocrystals. Our previous work demonstrates that the amount of water present in a solvothermal reaction with VO(acac)2 and lauric acid in toluene determines both the crystal phase of VO2 synthesized, as well as the length of the resulting nanorods. (21) Using this synthesis methodology, we varied the amount of water present in the reaction from 0.5 to 20 mmol (2–80 equiv per vanadium) in the presence of 4 equiv (1 mmol) of a selection of acids with varying pKa’s shown in Table 1. Figure 1 shows that, for each carboxylic acid examined here, a transition occurs from VO2(A) products (or product mixtures containing VO2(A)) to phase-pure VO2(B) products as the amount of water present in the reaction increases past a particular threshold concentration. This observation is consistent with our previously reported study in which the threshold concentration of water required for the formation of phase-pure VO2(B) in the presence of lauric acid (pKa = 5.3) was determined to be 5 mmol (20 equiv per vanadium). (21) Here we observe that decreasing the pKa of the carboxylic acid increases the threshold concentration of water required to obtain VO2(B) instead of VO2(A). For example, trifluoroacetic acid (pKa = 0.23) has a threshold concentration of 15 mmol (60 equiv per vanadium). Notably, the threshold water concentration observed in the absence of acidic ligands is 3 mmol (12 equiv per vanadium). This observation suggests that the minimum concentration of water required to form phase-pure VO2(B) is 12 equiv per vanadium center. Addition of carboxylic acids increases this threshold.

Figure 1

Figure 1. Plot of crystal phases obtained from solvothermal reactions of 0.25 mmol VO(acac)2 in toluene with 4 equiv (1 mmol) of carboxylic acid and varying water concentrations (2–100 equiv). Crystal structures were determined using powder X-ray diffraction, and the data can be found in the Supporting Information (Figures S1–S6).

High Resolution Image
Download MS PowerPoint Slide
Table 1. Aqueous pKa’s of Carboxylic Acids Used in the Synthesis of VO2 Nanocrystals
acidpKasolventreferences
lauric acid5.3water (22)
acetic acid4.76water (22)
benzoic acid4.20water (23)
4-nitrobenzoic acid3.44water (24)
trifluoroacetic acid0.23water (25)
We also observe that in the presence of very low concentrations of water (1 mmol or less), the addition of acetic, benzoic, 4-nitrobenzoic, and trifluoroacetic acid results in products whose powder X-ray diffraction patterns do not match that of either VO2(A) or VO2(B) (Figure 2). In the case of acetic acid, this pattern matches that of a previously reported VO(acetate)2 crystal structure. (26) This structure is a coordination polymer comprised of one-dimensional chains of corner-sharing octahedrally coordinated vanadium ions. Each vanadium ion is linked to each of its two neighboring vanadium ions by one bridging oxo ligand and two bridging bidentate acetate ligands. Analysis of single nanocrystals of the products obtained from reactions containing 4 equiv of benzoic or 4-nitrobenzoic acid and 4 equiv (1 mmol) of water by electron diffraction suggests that these products are the corresponding vanadyl carboxylate compounds─VO(benzoate)2 and VO(4-nitrobenzoate)2─and that these compounds also crystallize as one-dimensional chains of octahedrally coordinated vanadium ions with a structure that is entirely analogous to VO(acetate)2 (Figure 2, details of structural characterization in the Supporting Information). The powder X-ray diffraction pattern of the product obtained from the reaction of VO(acac)2 with 4 equiv of trifluoroacetic acid and 4 equiv of water resembles that of the other confirmed vanadyl carboxylate species. We therefore strongly suspect that this pattern corresponds to VO(trifluoroacetate)2. These data indicate that carboxylic acids can displace acetylacetonate, and 1 mmol (4 equiv) of water is insufficient to hydrolyze these species to form VO2. In a solvothermal reaction utilizing VO(benzoate)2 as a precursor in the absence of water and benzoic acid, the VO(benzoate)2 precursor is recovered. VO(benzoate)2 also forms upon reaction of 4 equiv of benzoic acid with VO(acac)2 in the absence of water under the same solvothermal conditions (200 °C for 24 h, see Supporting Information). This observation indicates that ligand exchange to form the VO(carboxylate)2 species does not require the presence of water.

Figure 2

Figure 2. (left) Powder X-ray diffraction spectra of products obtained from solvothermal reactions containing 1 equiv (0.25 mmol) VO(acac)2, 4 equiv (1 mmol) acid, 4 equiv (1 mmol) water, and 10 mL of toluene. The powder X-ray diffraction spectrum of the product obtained from a reaction containing 4 equiv of lauric acid and 120 equiv (30 mmol) of water is included for reference as an example of a VO2(B) nanocrystal product. Reference powder patterns for VO2(A) (JCPDS 00-042-0876, red) and VO2(B) (JCPDS 01-081-2392, black) are also included. (right) Crystal structures of the confirmed products include VO(4-nitrobenzoate)2 (top), VO(benzoate)2 (middle), and VO(acetate)2 (bottom).

High Resolution Image
Download MS PowerPoint Slide
The earliest reports of coordination polymers of VO(acetate)2, VO(benzoate)2, and VO(4-nitrobenzoate)2 state that these species are insoluble in most solvents, which is consistent with our observations. (27−29) Although VO(trifluoroacetate)2 has been reported previously as a soluble monomeric complex, (30) the species we isolated from the reaction of VO(acac)2 in the presence of 4 equiv each of trifluoroacetic acid and water is not soluble in polar or nonpolar solvents. We therefore suspect that this species is also a coordination polymer. VO(benzoate)2 and VO(4-nitrobenzoate)2 are reported to crash out immediately upon addition of vanadyl sulfate to an aqueous solution of the corresponding carboxylate, (29) indicating that monomeric carboxylate complexes cannot be isolated even in the presence of excess acid. Titration of acetic acid into aqueous solutions of the vanadyl ion VO2+ achieves a maximum of 1.5 bound acetates per solvated vanadium center, (31,32) indicating that stable solutions in which all monomeric species are bound to two acetate ligands cannot be achieved. Based on these previous reports, we conclude that monomeric vanadyl acetate, benzoate, or 4-nitrobenzoate species are highly unlikely to exist in nonpolar toluene solutions containing 4 equiv of carboxylic acid per vanadium, such as those used here.
In contrast to benzoic acid, reaction of lauric acid with VO(acac)2 in the absence of water produces no reaction─the recovered reaction mixture still contains lauric acid and VO(acac)2 (see Supporting Information). Furthermore, we note that formation of VO2(A) occurs in the presence of lauric acid and 0.5 or 1 mmol water, whereas at least 2 mmol water (8 equiv) is required to observe the formation of any VO2 species in the presence of acetic, benzoic, 4-nitrobenzoic, or trifluoroacetic acid (Figure 1). We suspect that formation of the one-dimensional vanadyl carboxylate coordination polymers and subsequent precipitation of these species impedes hydrolysis of the vanadium centers. We suspect that the steric bulk of the twelve-carbon chain in lauric acid prevents the formation of an analogous VO(laurate)2 coordination polymer, thereby leaving the vanadium centers more available for hydrolysis at low water concentrations. Although the powder X-ray diffraction data reported here and the FTIR data we reported previously (21) indicate that both VO(acac)2 and lauric acid are intact in the mixture recovered from a solvothermal reaction run in the absence of water, we cannot completely rule out the formation of some monomeric vanadyl laurate species in solution or the presence of a small fraction of such species in the recovered reaction mixture.
Previous reports have posited that the mechanism for the formation of VO2 from the solvothermal reaction of VO(acac)2 involves hydrolysis of VO(acac)2 to form [VO(H2O)5]2+ followed by condensation of this species to generate VO2. (17,18,21) This vanadyl aquo complex is stable under neutral aqueous conditions (33,34) and has a pKa of 5.3–6.0. (35) We proposed in our previous work that the relative rate of hydrolysis versus condensation controls whether VO2(A) or VO2(B) nuclei form. Slow hydrolysis enables condensation of partially hydrolyzed species, whereas faster hydrolysis promotes the formation of the fully hydrolyzed species before significant condensation occurs. We hypothesized that condensation of the fully hydrolyzed species favors the formation of VO2(B) nuclei, while condensation of partially hydrolyzed species favors the formation of VO2(A) nuclei. Here, we observe that addition of stronger carboxylic acids increases the threshold concentration of water required to obtain phase-pure VO2(B) nanocrystals instead of VO2(A). This observation is consistent with our hypothesis that the rate of hydrolysis controls the crystal phase of VO2 because increasing the strength of the organic acid should inhibit hydrolysis of VO(acac)2. More acidic reaction conditions result in a higher ratio of positively charged hydronium ions to water molecules, which lowers the concentration of neutrally charged water available to hydrolyze the VO(acac)2. Hydronium ions are much less nucleophilic than neutral water and therefore less reactive toward hydrolysis.
We further tested our hypothesis that slow hydrolysis promotes the formation of VO2(A) over VO2(B) by conducting a series of reactions in which we varied the relative concentrations of VO(acac)2, water, and trifluoroacetic acid (Figure 3). VO2(A) becomes the favored product as the concentration of either VO(acac)2 or trifluoroacetic acid increases relative to the concentration of water. Figure 3A shows that, when the amount of trifluoroacetic acid is fixed to 1 mmol, increasing the amount of VO(acac)2 from 0.25 to 1 mmol while keeping the concentration of water constant at 15 mmol results in a transition from VO2(B) products to VO2(A) products. Obtaining VO2(B) from a reaction containing 1 mmol of VO(acac)2 and 1 mmol trifluoroacetic acid requires increasing the amount of water present to at least 30 mmol, whereas VO2(B) can be obtained using only 15 mmol of water in the presence of 0.25 mmol of VO(acac)2 and 1 mmol trifluoroacetic acid. Figure 3B shows that similar results are obtained when the amount of VO(acac)2 is kept constant at 0.25 mmol and the ratio of trifluoroacetic acid to water is increased by either decreasing the concentration of water or increasing the concentration of acid. In both cases, higher ratios of trifluoroacetic acid to water favor the formation of VO2(A).

Figure 3

Figure 3. Plots of the crystal phase of VO2 nanocrystals obtained from reaction mixtures containing (A) various concentrations of VO(acac)2 and water with a constant concentration of trifluoroacetic acid, and (B) various concentrations of trifluoroacetic acid and water with a constant concentration of VO(acac)2. The amounts of reagents used in each of these reactions are tabulated in Table S3, and the powder X-ray diffraction spectra used to construct these plots are shown in the Supporting Information (Figures S9–S12).

High Resolution Image
Download MS PowerPoint Slide
Since the presence of strong carboxylic acids favors the formation of VO2(A) and VO2(A) is a more thermodynamically stable phase than VO2(B), we investigated whether strong carboxylic acids could mediate the conversion of VO2(B) nanocrystals to VO2(A). Previous reports show that conversion from VO2(B) to VO2(A) is possible under solvothermal conditions at high temperatures. (3,9) For example, Zhang, et al. obtained VO2(A) nanocrystals upon reacting a solution containing VO2(B) nanocrystals and water at 260 or 280 °C for 48 h. (3) Additionally, another report also heated VO2(B) nanocrystals to 280 °C under hydrothermal conditions for 48 h to convert them to VO2(A). (9) We investigated the possibility that lowering the temperature and using an acidic reaction environment could also instigate this transformation. Figure 4 demonstrates that VO2(B) nanocrystals can indeed be converted to VO2(A) when heated in toluene in the presence of 4 equiv of trifluoroacetic acid and 20 equiv of water at 230 °C over the course of 120 h. This conversion is indicated by the coalescence of two pairs of diffraction peaks at 2θ = 14.4 and 15.3° and 2θ = 29 and 30.2° into single peaks at 2θ = 15 and 30°, respectively. The resulting peaks correspond to the (110) and (220) planes of the VO2(A) structure. The overall decrease in the number of diffraction peaks signals an increase in symmetry as the monoclinic VO2(B) structure converts to the tetragonal VO2(A) structure. The VO2(A) nanocrystals obtained from this reaction are smaller than the initial VO2(B) nanocrystals (Figure 4). This change in morphology indicates that the trifluoroacetic acid may induce dissolution of the VO2(B) nanocrystals and re-nucleation as VO2(A), possibly using VO(trifluoroacetate)2 as a reaction intermediate. We note that in reactions containing VO(acac)2, lauric acid, and 2 or 20 equiv of water, we do not observe any indications of phase interconversion over the course of a 24 h reaction period. Examining products present in these reaction mixtures after various reaction times reveals that only one type of crystalline product is observed per reaction condition: VO2(A) for the reaction containing 2 equiv of water and VO2(B) for the reaction containing 20 equiv of water (see Supporting Information). This observation implies that for reactions starting from VO(acac)2, the final VO2 product phase nucleates directly from condensation of hydroxylated species formed upon precursor hydrolysis.

Figure 4

Figure 4. (A) Powder X-ray diffraction spectra of nanocrystals obtained from solvothermal reactions of VO2(B) nanocrystals in toluene with 20 equiv of water and 4 equiv of trifluoroacetic acid at 230 °C demonstrate the transformation from VO2(B) to VO2(A) after 120 h of reaction time. The black dotted rectangles highlight the pairs of diffraction peaks in VO2(B) that coalesce to form the peaks associated with diffraction of the (110) and (220) planes of VO2(A). (B,C) TEM images of (B) the VO2(B) nanocrystals used as the starting material and (C) the VO2(A) nanocrystals obtained after reacting the nanocrystals shown in B in toluene with 20 equiv of water and 4 equiv of trifluoroacetic acid at 230 °C for 120 h. The scale bars correspond to 200 nm.

High Resolution Image
Download MS PowerPoint Slide
After establishing that the acidity of the carboxylic acid ligands impacts the phase of VO2 nanocrystals, we next investigated the impact of tuning the steric bulk of the carboxylic acid ligand on the solvothermal synthesis of VO2 nanocrystals. A selection of aliphatic carboxylic acids with varying carbon-chain lengths was chosen, specifically butyric (4C), hexanoic (6C), heptanoic (7C), decanoic (10C), lauric (12C), and stearic (18C) acid. All of these carboxylates have relatively similar pKa’s of ∼4.8–5.3. (22,36) Figure S14 in the Supporting Information shows powder X-ray diffraction spectra obtained from reactions of VO(acac)2 in the presence of 4 equiv of each of these acids and 20 equiv of water. These data demonstrate that VO2(B) is obtained in every case. Likewise, the morphology of the nanocrystals remains constant with variation of the ligand chain length, except for stearic acid, as shown in Figure S14. Reactions containing aliphatic carboxylic acids with chain lengths less than 18 carbons produce VO2(B) nanorods of average length 110–150 nm, while stearic acid yields nanoplatelets in addition to nanorods. Overall, since only one of the aliphatic carboxylic acids resulted in a difference in morphology, we conclude that varying the length of aliphatic carboxylic acids does not strongly influence the hydrolysis and growth of VO2(B) nanocrystals.
We also compared the morphologies of VO2(B) nanocrystals synthesized with carboxylic acids of various pKa’s. Since all of the acids produce phase-pure VO2(B) with 60 equiv of water, these products were analyzed by scanning electron microscopy (SEM, Figure 5). The reactions with no ligand, lauric acid, and acetic acid all showed nanorod morphologies, while the reactions with benzoic acid and 4-nitrobenzoic acid resulted in a mixture of platelets and nanorods. Although the exact mechanism governing the change in morphology from rods to platelets is unclear, we note that the nanoplatelet morphology affords a larger flat surface area that may promote stabilizing intermolecular interactions between surface-bound ligands, such as π–π interactions between the aromatic acids. We also observe a mixture of nanoplatelet and nanorod products from reactions that contain stearic acid. Long carbon chains are also known to engage in stabilizing intermolecular van der Waal’s interactions on flat surfaces. (37)

Figure 5

Figure 5. SEM images of reactions with 1 equiv (0.25 mmol) VO(acac)2, 60 equiv (15 mmol) water, and 4 equiv (1 mmol) of (A) no ligand, (B) lauric acid, (C) acetic acid, (D) benzoic acid, (E) 4-nitrobenzoic acid, and (F) trifluoroacetic acid. Each image contains a scale bar corresponding to 1 μm.

High Resolution Image
Download MS PowerPoint Slide
Finally, the reaction containing trifluoroacetic acid produced nanocarambolas, which are elongated aggregates of stacked nanosheets whose cross section resembles a six-pointed star. (38) This morphology was previously observed in the synthesis of VO2(B) nanocrystals from VO(acac)2 in the presence of polyvinylpyrrolidone (PVP) (18) and from V2O5 in the presence of oxalic acid. (7) The first study discovered that changing the concentration of PVP in the reaction impacted the morphology of the resulting nanocrystals. Nanorods formed in the absence of PVP, while addition of 3 mg/L PVP formed nanoflowers, and 54 mg/L PVP formed nanocarambolas. (18) Thus, the change in morphology from nanoflowers to nanocarambolas occurred after an increase in PVP concentration by a factor of 18. The second study found that using 0.06 mol/L oxalic acid produced nanorods, while 0.12 mol/L oxalic acid produced a mixture of nanobundles and nanocarambolas. (7) Both of these studies concluded that the interaction of ligands with the surface of the nanocrystal during growth impacts the final morphology. (7,18,38)
To explore the mechanism by which the unusual nanocarambola morphology forms, we varied the duration of the reactions run in the presence of trifluoroacetic acid (see Supporting Information). At early reaction times (3 h), we observe nanorods with short rod-like protrusions growing perpendicular to the long axis. After 6 h, we observe fully formed nanocarambolas. We hypothesize that the short protrusions observed at early times expand along the long axis of the original nanorod, forming sheets that result in the 6-armed nanocarambola structure. Unlike other carboxylic acids used here, trifluoroacetic acid has two moieties that can engage in strong interactions with the nanocrystal surface: the carboxylate group and the fluorine atoms. Carboxylic acid groups are well known to bind to the surfaces of metal oxide nanoparticles. (39,40) In the case of TiO2, trifluoroacetic acid ligands were found to have a similar structure-directing effect as the addition of HF─both additives resulted in the stabilization of {001} facets and the formation of nanosheets in the case of HF and a mixture of nanosheets and truncated octahedrons in the case of trifluoroacetic acid. (41) The authors also observed that aliphatic carboxylic acids, such as oleic acid, form truncated octahedrons, indicating that the carboxylate group also stabilizes {001} facets but not to the same extent as fluoride ions. The authors attributed the intermediate structure-directing effect of trifluoroacetic acid to its partial degradation under solvothermal reaction conditions to form fluoride ions. We suspect that similar degradation of a fraction of the trifluoroacetic acid molecules may be responsible for the formation of VO2(B) nanocarambolas.

Conclusions

Click to copy section linkSection link copied!
Our work demonstrates the effects of the acidity of the reaction mixture on the crystal phase and morphology of vanadium dioxide nanocrystals obtained under solvothermal reaction conditions. Decreasing the pKa and increasing the concentration of carboxylic acid ligands present in the reaction mixture while keeping the concentration of water constant favors the formation of VO2(A), whereas increased pKa and decreased acid concentration favor the formation of VO2(B). Furthermore, increasing the concentration of the precursor relative to the concentration of water leads to VO2(A), whereas VO2(B) forms from reaction mixtures containing lower precursor-to-water ratios. These observations are consistent with our hypothesis that the rate of precursor hydrolysis relative to condensation controls which crystal phase nucleates. We identified VO(carboxylate)2 species as likely reaction intermediates formed prior to nucleation of the VO2 species. Finally, our results suggest that acidity alone likely does not have a strong impact on nanocrystal morphology. Instead, interactions involving substituents on the carboxylic acid ligands, such as intermolecular π–π interactions or interactions between fluoride ions formed upon degradation of −CF3 groups and the nanocrystal surface, may play a significant role in determining the morphology of VO2(B) nanocrystals. Overall, this work provides important insight into how carboxylic acids impact the crystal phase and morphology of VO2 nanocrystals.

Experimental Methods

Click to copy section linkSection link copied!

General Considerations

Prior to the addition of water to the reaction mixtures, all manipulations were carried out in an MBraun inert atmosphere glovebox under a nitrogen atmosphere unless otherwise stated. Autoclave reactors and Teflon liners were pumped down in an evacuated antechamber overnight prior to use in the glovebox. Molecular sieves (3 Å, Fisher Scientific) were activated by heating at 200 °C under vacuum overnight. Toluene was dried over activated sieves (20% by weight) for at least 24 h, then purged with nitrogen for at least 1 h before being transferred via a cannula to a Schlenk flask. Toluene was then pumped into the glove box overnight in an evacuated antechamber and stored over activated 3 Å molecular sieves. VO(acac)2, stearic acid, decanoic acid, heptanoic acid, hexanoic acid, and butyric acid purchased from Sigma-Aldrich and lauric acid purchased from Millipore were pumped into the glovebox overnight in an evacuated antechamber before use. Benzoic acid and 4-nitrobenzoic acid purchased from Oakwood, acetic acid purchased from Fisher Scientific, and trifluoroacetic acid purchased from Sigma-Aldrich were used without further purification.

Safety Considerations

Trifluoroacetic acid is both volatile and corrosive and should therefore be handled exclusively in a fume hood. Autoclave reactors become pressurized at elevated temperatures and should be handled with care. No attempts should be made to open autoclave reactors unless they are at room temperature.

Synthesis of VO2 Nanocrystals in the Presence of Different Carboxylic Acids

A 25 mL Teflon-lined autoclave reactor was charged with 0.25 mmol (0.068 g) VO(acac)2 and 10 mL of toluene inside a nitrogen-filled glovebox. The autoclave reactor was sealed and removed from the glovebox. In ambient air, the autoclave reactor was opened, and the desired amount of water was added (3–20 mmol). A carboxylic acid (1 mmol) was added to the reaction mixture either before (stearic, lauric, decanoic, heptanoic, hexanoic, or butyric) or after (lauric, acetic, benzoic, 4-nitrobenzoic, or trifluoroacetic acid) removal from the glovebox. Tables S1 and S4 in the Supporting Information contain detailed lists of the masses and volumes of the various reagents used in these reactions. After the addition of water, the autoclave reactor was sealed again and heated in an oven at 200 °C for 24 h before it was removed and allowed to cool to room temperature. The black solid product was collected by centrifugation under ambient conditions and washed with ethanol. The product was rotovapped to dryness and stored in the glovebox under nitrogen.

Synthesis of VO2 Nanocrystals with Various Concentrations of Precursor, Water, and Acid

A 25 mL Teflon-lined autoclave reactor was charged with the desired amount of VO(acac)2 (0.075–3 mmol) and 10 mL of toluene. The autoclave reactor was sealed and removed from the glovebox. In ambient air, the autoclave reactor was opened and the desired amounts of water (0.5–20 mmol) and trifluoroacetic acid (0.5–4 mmol) were added (see Table S3 in the Supporting Information for the details of each individual reaction reported here). The autoclave reactor was sealed again and heated in an oven at 200 °C for 24 h before it was removed from the oven and allowed to cool to room temperature. The black solid product was collected by centrifugation under ambient conditions and washed with ethanol. The product was rotovapped to dryness and stored in the glovebox under nitrogen. Vanadyl carboxylate products were collected and purified using procedures identical to those used for the vanadium dioxide nanocrystals.

Nanocrystal Characterization

Powder X-ray diffraction measurements were performed using a Rigaku XtaLAB Synergy-S Dualflex single-crystal diffractometer operating in the powder collection mode using Cu Kα radiation. Nanocrystalline powders were affixed to a Nylon loop (0.1 mm inner diameter) with a light coating of viscous oil and mounted on a goniometer for data collection. An FEI Tecnai F20 G2 scanning transmission electron microscope operated at 200 kV and a Zeiss Auriga scanning electron microscope with an InLens detector operated at 5–20 kV were used to analyze the morphology of the VO2 nanocrystals. Single nanocrystals of VO(benzoate)2 and VO(4-nitrobenzoate)2 were structurally analyzed using a Rigaku XtaLAB Synergy-ED electron diffractometer equipped with a HyPix-ED detector (see Supporting Information for details).

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnanoscienceau.3c00014.

  • Tables reporting the amounts of all reagents used in each reaction reported here, powder X-ray diffraction spectra, TEM, and SEM images of nanocrystalline products, and details of the characterization of VO(benzoate)2 and VO(4-nitrobenzoate)2 by single-crystal electron diffraction (PDF)

  • Crystallographic data for VO(benozate)2 (CIF)

  • Crystallographic data for VO(4-nitrobenzoate)2 (CIF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
  • Authors
    • Brittney A. Beidelman - Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
    • Xiaotian Zhang - Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
    • Ellen M. Matson - Department of Chemistry, University of Rochester, Rochester, New York 14627, United States;  Orcidhttps://orcid.org/0000-0003-3753-8288
  • Author Contributions

    B.A.B. and K.E.K. conceived of the project, B.A.B. and X.Z. carried out all solvothermal reactions, B.A.B. characterized nanocrystal products, E.M.M. assisted with interpretation of data, B.A.B. and K.E.K. wrote the manuscript. CRediT: Brittney A. Beidelman conceptualization (equal), data curation (lead), formal analysis (lead), investigation (lead), methodology (lead), validation (lead), visualization (equal), writing-original draft (equal), writing-review & editing (equal); Xiaotian Zhang data curation (supporting), formal analysis (supporting), investigation (supporting), methodology (supporting), validation (supporting); Ellen M. Matson conceptualization (supporting), funding acquisition (supporting), project administration (supporting), supervision (supporting), writing-review & editing (supporting); Kathryn E. Knowles conceptualization (equal), formal analysis (supporting), funding acquisition (lead), project administration (lead), resources (lead), supervision (lead), visualization (equal), writing-original draft (equal), writing-review & editing (equal).

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

This work was supported financially by a Negative Emissions Sciences Scialog grant funded by the Alfred P. Sloan foundation (G-2021-14157). E.M.M. is the recipient of a Camille Dreyfus Teacher-Scholar Award, which has also supported this work. Dr. Akihito Yamano and Dr. Sho Ito of Rigaku Corp. in Japan performed the electron diffraction experiments on the nanocrystals to obtain crystallographic data for the VO(benzoate)2 and VO(4-nitrobenzoate)2 structures. Dr. Lee Daniels and Dr. Joseph Ferrara of Rigaku Americas Corp. in the USA performed the structural solving analysis for these new structures. We also acknowledge William W. Brennessel from the University of Rochester for his assistance in collecting the powder X-ray diffraction data.

References

Click to copy section linkSection link copied!

This article references 41 other publications.

  1. 1
    Wu, C.; Feng, F.; Xie, Y. Design of vanadium oxide structures with controllable electrical properties for energy applications. Chem. Soc. Rev. 2013, 42, 5157– 5183,  DOI: 10.1039/c3cs35508j
    Google Scholar
    1
    Design of vanadium oxide structures with controllable electrical properties for energy applications
    Wu, Changzheng; Feng, Feng; Xie, Yi
    Chemical Society Reviews (2013), 42 (12), 5157-5183CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. The elec. properties of inorg. materials has been a long-standing pursued research topic, and successfully controlling the elec. property of an inorg. material has attracted significant attention for a wide range of energy-related applications, covering energy storage, energy conversion and energy utilization. During the few past decades, vanadium oxides have been studied to gain a clear picture of how microstructural characteristics generating the e-e correlations influence the electronic structure of a material, through which the charge concn., elec. cond. as well as the metal-insulator transition (MIT), etc., can be precisely controlled, giving promising signs for constructing energy-related devices. In this review, we present an extensive review of the engineering of the microstructures of vanadium oxides with control of their elec. properties, and with attempts to rationally construct energy-related devices, such as aq. lithium ion batteries, supercapacitors for energy storage, and thermoelec. generators for energy conversion. Furthermore, the MIT performance of vanadium oxides has also seen tremendous advantages for the applications of "smart windows" and magnetocaloric refrigerators for energy utilization. Collectively, progresses to date suggest that in vanadium oxide systems, the elec. properties, including elec. cond., carrier concns., and the MIT performance, were all strongly dependent on the microstructural characteristics at the at. scale, which have presented extensive promising energy applications covering energy storage, energy conversion and energy utilization.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXot1ersr8%253D&md5=ddc30e955f7e900d2efa35cb65c64809
  2. 2
    Li, M.; Magdassi, S.; Gao, Y.; Long, Y. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows. Small 2017, 13, 1701147,  DOI: 10.1002/smll.201701147
    Google Scholar
    There is no corresponding record for this reference.
  3. 3
    Zhang, Y.; Fan, M.; Liu, X.; Xie, G.; Li, H.; Huang, C. Synthesis of VO2(A) nanobelts by the transformation of VO2(B) under the hydrothermal treatment and its optical switching properties. Solid State Commun. 2012, 152, 253– 256,  DOI: 10.1016/j.ssc.2011.11.036
    Google Scholar
    3
    Synthesis of VO2(A) nanobelts by the transformation of VO2(B) under the hydrothermal treatment and its optical switching properties
    Zhang, Yifu; Fan, Meijuan; Liu, Xinghai; Xie, Guangyong; Li, Houbin; Huang, Chi
    Solid State Communications (2012), 152 (4), 253-256CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)
    VO2(A) nanobelts had been successfully synthesized by the transformation of VO2(B) using H2O as the solvent under the hydrothermal approach at 280 °C for 48 h. Some parameters, such as the reaction temp. and time, had been briefly discussed to reveal the transition from VO2(B) to VO2(A). It was found that H2O played a crucial role in the transition from VO2(B) to VO2(A). The phase transition of VO2(A) nanobelts was at 162 °C. The optical switching properties of VO2(A) were studied by the variable-temp. IR spectra for the first time. In addn., VO2(A) nanobelts were calcined at 700 °C for 2 h under a high purity Ar (99.999%) atm. to obtain VO2(M) which exhibited a strong crystallog. transition at around 65 °C.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpsFOjsA%253D%253D&md5=e99134ae24630224d8694450f8f372fd
  4. 4
    Liu, P.; Zhu, K.; Gao, Y.; Wu, Q.; Liu, J.; Qiu, J.; Gu, Q.; Zheng, H. Ultra-long VO2(A) nanorods using the high-temperature mixing method under hydrothermal conditions: synthesis, evolution and thermochromic properties. CrystEngComm 2013, 15, 2753– 2760,  DOI: 10.1039/c3ce27085h
    Google Scholar
    4
    Ultra-long VO2 (A) nanorods using the high-temperature mixing method under hydrothermal conditions: synthesis, evolution and thermochromic properties
    Liu, Pengcheng; Zhu, Kongjun; Gao, Yanfeng; Wu, Qingliu; Liu, Jinsong; Qiu, Jinhao; Gu, Qilin; Zheng, Hongjuan
    CrystEngComm (2013), 15 (14), 2753-2760CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    Well-crystd., ultra-long VO2 (A) nanorods were prepd. using a facile high-temp. mixing method (HTMM) under hydrothermal conditions. The as-obtained products were characterized by x-ray diffraction, field-emission SEM, transmission electron microscopy, XPS, UV-Vis-NIR, DSC, and FTIR. The effect of W doping on the phase-transition properties of VO2(A) was also studied. The optimal condition of VO2(A) using the HTMM is hydrothermal treatment at 240° for 48 h with a 3:1 molar ratio of the reducing agent to the vanadium source. The reason why the polymorphic forms of VO2 show different colors is that the light in the visible region reflected by the samples is different. The phase-transition temp. of the pure VO2 (A) is 154.75°, which is significantly lower than the 162 °C reported previously. When a small amt. of W is doped, VO2(A) will be transformed into other polymorphic forms, which indicates that the crystal structure of VO2(A) is highly sensitive to limited doping. Importantly, the as-obtained pure VO2(A) shows good thermochromic properties and optical-switching characters. A crystal growth mechanism for VO2(A), oriented-attachment-exfoliation-recrystn.-oriented-attachment, is proposed and described in detail.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjslKgs78%253D&md5=24b8f349248f47c43ba3f776251a7173
  5. 5
    Subba Reddy, C. V.; Walker, E. H., Jr.; Wicker, S. A., Sr.; Williams, Q. L.; Kalluru, R. R. Synthesis of VO2(B) nanorods for Li battery application. Curr. Appl. Phys. 2009, 9, 1195– 1198,  DOI: 10.1016/j.cap.2009.01.012
    Google Scholar
    There is no corresponding record for this reference.
  6. 6
    Soltane, L.; Sediri, F. Rod-like nanocrystalline B-VO2: Hydrothermal synthesis, characterization and electrochemical properties. Mater. Res. Bull. 2014, 53, 79– 83,  DOI: 10.1016/j.materresbull.2014.01.046
    Google Scholar
    6
    Rod-like nanocrystalline B-VO2: Hydrothermal synthesis, characterization and electrochemical properties
    Soltane, L.; Sediri, F.
    Materials Research Bulletin (2014), 53 (), 79-83CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
    Rod-like nanocryst. VO2(B) has been successfully synthesized via a simple hydrothermal process by using V2O5 as vanadium source and 4-butylaniline H3C-(CH2)3-(C6H4)-NH2 as reducing and structure directing agent. The compds. were analyzed through X-ray diffraction (XRD), SEM (SEM), Fourier transform IR spectroscopy (FTIR), Raman spectroscopy and UV-visible spectroscopy. The VO2(B) nanorods are up to several micrometers in length and about 80 nm in thickness with a large optical band gap of ∼2.709 eV. Thin films of VO2(B) nanorods deposited on ITO substrates were electrochem. characterized by cyclic voltammetry. The voltammograms show reversible redox behavior with charge-discharge cycling process corresponding to the reversible lithium intercalation/deintercalation into the crystal lattice. The av. coulombic efficiency to this redox processes is upper 98% during the electrochem. measurements.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmsFCmtLk%253D&md5=8b9e591eaf47af46b4d92ff3dd4afc0a
  7. 7
    Yin, H.; Yu, K.; Zhang, Z.; Zhu, Z. Morphology-control of VO2(B) nanostructures in hydrothermal synthesis and their field emission properties. Appl. Surf. Sci. 2011, 257, 8840– 8845,  DOI: 10.1016/j.apsusc.2011.04.079
    Google Scholar
    7
    Morphology-control of VO2 (B) nanostructures in hydrothermal synthesis and their field emission properties
    Yin, Haihong; Yu, Ke; Zhang, Zhengli; Zhu, Ziqiang
    Applied Surface Science (2011), 257 (21), 8840-8845CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
    VO2 (B) nanostructures were synthesized via a facile hydrothermal process using V2O5 as source material and oxalic acid as reductant. Three nanostructures of nanorods, nanocarambolas and nanobundles were found existing in the products, and a continuous changing of morphol. was found in the synthesis process, during which the proportion of these three types of nanostructures can be adjusted by altering the concns. of oxalic acid. The microstructures were evaluated using X-ray diffraction, SEM and TEM. Field emission (FE) properties of these three types of nanostructures showed that the nanobundles have the best field emission performance with a turn-on field of ∼1.4 V/μm and a threshold field of ∼5.38 V/μm. These characteristics make VO2 (B) nanostructures a competitive cathode material in field emission devices.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXos1egsr0%253D&md5=8e63026251f96878a79d78084f070814
  8. 8
    Ganganagappa, N.; Siddaramanna, A. One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery. Mater. Charact. 2012, 68, 58– 62,  DOI: 10.1016/j.matchar.2012.03.010
    Google Scholar
    8
    One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery
    Ganganagappa, Nagaraju; Siddaramanna, Ashoka
    Materials Characterization (2012), 68 (), 58-62CODEN: MACHEX; ISSN:1044-5803. (Elsevier)
    One of the metastable phases of vanadium dioxide, VO2(B) bundles of nanorods and microspheres have been synthesized through a simple hydrothermal method by dispersing V2O5 in aq. quinol. The obtained products were characterized by X-ray diffraction (XRD), Fourier transform IR (FTIR) spectroscopy, SEM (SEM) and electrochem. discharge-charge test for lithium battery. It was found that the morphologies of the obtained VO2(B) can be tuned by manipulating the relative amt. of quinol. The electrochem. test found that the bundles of nanorods exhibit an initial discharge capacity of 171 mAh g- 1 and its almost stabilized capacity was reached to 108 mAh g- 1 after 47 cycles at a c.d. of 0.1 mA g- 1. The formation mechanism of the VO2(B) bundles of nanorods and microspheres was also discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XntFyksLY%253D&md5=1aa9780a7480b9a28d9680b529a2636e
  9. 9
    Zhang, Y. VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties. Mater. Sci.-Pol. 2016, 34, 169– 176,  DOI: 10.1515/msp-2016-0023
    Google Scholar
    9
    VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties
    Zhang, Yifu
    Materials Science-Poland (2016), 34 (1), 169-176CODEN: MSACDV; ISSN:2083-134X. (Walter de Gruyter GmbH)
    Vanadium dioxide VO2 has been paid in recent years increasing attention because of its various applications, however, its oxidn. resistance properties in air atm. have rarely been reported. Herein, VO2(B) nanobelts were transformed into VO2(A) and VO2(M) nanobelts by hydrothermal route and calcination treatment, resp. Then, we comparatively studied the oxidn. resistance properties of VO2(B), VO2(A) and VO2(M) nanobelts in air atm. by thermo-gravimetric anal. and DTA (TGA/DTA). It was found that the nanobelts had good thermal stability and oxidn. resistance below 341°C, 408°C and 465°C in air, resp., indicating that they were stable in air at room temp. The fierce oxidn. of the nanobelts occurred at 426, 507 and 645°C, resp. The results showed that the VO2(M) nanobelts had the best thermal stability and oxidn. resistance among the others. Furthermore, the phase transition temps. and optical switching properties of VO2(A) and VO2(M) were studied by differential scanning calorimetry (DSC) and variable temp. IR spectra. It was found that the VO2(A) and VO2(M) nanobelts had outstanding thermochromic character and optical switching properties.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XnvFWgtLg%253D&md5=824fffaabc1ee70900b734e7cb8ed72d
  10. 10
    Sediri, F.; Gharbi, N. Controlled hydrothermal synthesis of VO2(B) nanobelts. Mater. Lett. 2009, 63, 15– 18,  DOI: 10.1016/j.matlet.2008.08.022
    Google Scholar
    There is no corresponding record for this reference.
  11. 11
    Wang, Q.; Xu, J.; Zhang, W.; Mao, M.; Wei, Z.; Wang, L.; Cui, C.; Zhu, Y.; Ma, J. Research progress on vanadium-based cathode materials for sodium ion batteries. J. Mater. Chem. A 2018, 6, 8815– 8838,  DOI: 10.1039/c8ta01627e
    Google Scholar
    11
    Research progress on vanadium-based cathode materials for sodium ion batteries
    Wang, Qinghong; Xu, Jiantie; Zhang, Wenchao; Mao, Minglei; Wei, Zengxi; Wang, Lei; Cui, Chunyu; Zhu, Yuxuan; Ma, Jianmin
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (19), 8815-8838CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    A review is presented. Sodium ion batteries (SIBs) have attracted increasing attention as one of the most promising candidates for cost-effective, high-energy rechargeable batteries. Owing to their high theor. capacity and energy d., and rich electrochem. interaction with Na+ (V2+-V5+), a large no. of vanadium(V)-based cathode materials, including vanadium oxides (e.g., V2O5 and VO2), vanadium bronzes (e.g., NaxVO2, NaV3O8, NaV6O15 and δ-NH4V4O10), V-based phosphates (e.g., Na3V2(PO4)3, VOPO4, NaVOPO4, Na7V3(P2O7)4 and Na2(VO)P2O7) and F-contg. V-based polyanions (e.g., NaVPO4F, Na3V2(PO4)2F3 and Na3(VOx)2(PO4)2F3-2x), have been explored for SIBs. In this review, we mainly summarize the basic structures, modified/optimized structures, synthetic methods and morphol. control of V-based cathode materials for SIBs. Addnl., major drawbacks, emerging challenges and some perspectives on the development of V-based cathode materials for SIBs are also discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXntlCnsrs%253D&md5=32772400483c5ac72c28bae062b824d9
  12. 12
    Zhang, L.; Yao, J.; Guo, Y.; Xia, F.; Cui, Y.; Liu, B.; Gao, Y. VO2(A) Nanorods: One-pot Synthesis, Formation Mechanism and Thermal Transformation to VO2(M). Ceram. Int. 2018, 44, 19301– 19306,  DOI: 10.1016/j.ceramint.2018.07.157
    Google Scholar
    12
    VO2(A) nanorods: One-pot synthesis, formation mechanism and thermal transformation to VO2(M)
    Zhang, Liangmiao; Yao, Jianing; Guo, Yunfeng; Xia, Fang; Cui, Yuanyuan; Liu, Bin; Gao, Yanfeng
    Ceramics International (2018), 44 (16), 19301-19306CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
    The monoclinic VO2(M) has promising applications in intelligent devices but its prepn. still requires improvement to permit cost-effective mass prodn. In this work, we report a 2-stage approach for producing VO2(M) nanorods by (1) hydrothermal redn. of vanadium pentoxide by sodium bisulfate at 220°C to form VO2(A), and (2) subsequent thermal activated phase transformation of VO2(A) to VO2(M) at 350-450°C in vacuum. The obtained VO2(M) nanorods showed a reversible phase transition temp. at about 62.5°C and a narrow thermal hysteresis width of 10°C. The mechanism of the hydrothermal redn. was studied by combined ex situ microscopic and diffraction characterization of cooled samples as well as in situ PXRD expts., in which the hydrothermal synthesis was monitored in real time by time-resolved diffraction datasets. It was found that the hydrothermal synthesis of VO2(A) is a 4-step process: (1) redn. of V2O5 to form VO2(B) nanoparticles, (2) oriented attachment of VO2(B) nanoparticles along the [110] direction, (3) formation of VO2(B) nanorods as a results of oriented attachments, and (4) hydrothermal transformation of the metastable intermediate VO2(B) nanorods to VO2(A) nanorods. This clear understanding of the mechanism will help the further optimization of synthesis temp. and time for prepg. VO2(A). This method provides a low temp. thermal treatment alternative and hence helps the redn. of cost for the prodn. of VO2(M), bring the mass application of VO2(M) one step closer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVartb3L&md5=b980416b5b434be3ddf18b028717cc1c
  13. 13
    Popuri, S.; Artemenko, A.; Labrugere, C.; Miclau, M.; Villesuzanne, A.; Pollet, M. VO2(A) Reinvestigation of crystal structure, phase transition and crystal growth mechanisms. J. Solid State Chem. 2014, 213, 79– 86,  DOI: 10.1016/j.jssc.2014.01.037
    Google Scholar
    There is no corresponding record for this reference.
  14. 14
    Ji, S.; Zhang, F.; Jin, P. Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure. J. Solid State Chem. 2011, 184, 2285– 2292,  DOI: 10.1016/j.jssc.2011.06.029
    Google Scholar
    14
    Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure
    Ji, Shidong; Zhang, Feng; Jin, Ping
    Journal of Solid State Chemistry (2011), 184 (8), 2285-2292CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
    VO2(A) usually occurs during the prepn. of VO2 polymorphs. This leads to an ambiguous understanding of the transformation between VO2 polymorphs. The calcn. of the ground state energies for different VO2 polymorphs indicated that there is only a small energy gap between VO2(A) and VO2(R), which suggests that the transformation from VO2(A) to VO2(R) should be pressure sensitive. This hypothesis was verified during the synthesizing of VO2 polymorphs by reducing V2O5 with oxalic acid through hydrothermal treatment process. Selective formation of pure phase VO2(A) or VO2(R) was achieved by controlling the hydrothermal pressure through varying the filling ratio at 270°. It was found that a filling ratio >0.5 favors the formation of pure VO2(R) while a filling ratio ≤0.4 results in the formation of VO2(A). Based on our expts., VO2(B) nanobelts always formed first and then transformed to VO2(A) by an assembling process at increased temp. or extended reaction time. Under further higher pressure, the VO2(A) transformed spontaneously to VO2(R) initialized from the vol. shrinkage due to the formation of denser VO2(R).
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1Cms7Y%253D&md5=7be35329c5ffd268cc056cfdda465286
  15. 15
    Cheng, X. H.; Xu, H. F.; Wang, Z. Z.; Zhu, K. R.; Li, G.; Jin, S. Synthesis, characterization and formation mechanism of metastable phase VO2(A) nanorods. Mater. Res. Bull. 2013, 48, 3383– 3388,  DOI: 10.1016/j.materresbull.2013.05.016
    Google Scholar
    15
    Synthesis, characterization and formation mechanism of metastable phase VO2(A) nanorods
    Cheng, X. H.; Xu, H. F.; Wang, Z. Z.; Zhu, K. R.; Li, G.; Jin, Shaowei
    Materials Research Bulletin (2013), 48 (9), 3383-3388CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
    Pure phase VO2(A) nanorods were synthesized via the redn. of V2O5 by oxalic acid during the hydrothermal treatment. Two sets of samples were prepd. by varying both system temp. and reaction time under a filling ratio of 0.40 for observing the formation and evolution of VO2(A) nanorods. Structures were characterized by X-ray diffraction, scanning and transmission electron microscopies, resp. It was found that VO2(B) was firstly formed and then transformed into VO2(A) as the increasing system temp. or extending reaction time. An assembling and following crystal adjustment was proposed for explanation the formation process of VO2(A) from VO2(B). For VO2(A) nanorods, the phase transition temp. of 169.7°C was higher than that of the VO2(A) bulk, it might be ascribed to the lower crystallinity or nonstoichiometry in VO2(A) nanorods. VO2 nanostructures with controllable phases and properties should find their promising applications in a single VO2 nanodevice.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXovVCms7c%253D&md5=a5f9bc3aa90d57928080e541829afa04
  16. 16
    Zhang, L.; Xia, F.; Song, Z.; Webster, N. A. S.; Luo, H.; Gao, Y. Synthesis and formation mechanism of VO2(A) nanoplates with intrinsic peroxidase-like activity. RSC Adv. 2015, 5, 61371– 61379,  DOI: 10.1039/c5ra11014a
    Google Scholar
    16
    Synthesis and formation mechanism of VO2(A) nanoplates with intrinsic peroxidase-like activity
    Zhang, Liangmiao; Xia, Fang; Song, Zhengdong; Webster, Nathan A. S.; Luo, Hongjie; Gao, Yanfeng
    RSC Advances (2015), 5 (75), 61371-61379CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    Monocryst. VO2(A) nanoplates were synthesized via a 1-pot hydrothermal process. In situ powder x-ray diffraction was used to monitor the hydrothermal synthesis and VO2(A) nucleates and grows directly from soln. after the complete hydrolysis of a 2.0M VO(acac)2 precursor soln., rather than involving a previously reported intermediate phase VO2(B). A hydrating-exfoliating-splitting mechanism was established to explain the formation of the nanoplate architecture. The synthesized VO2(A) nanoplates showed outstanding peroxidase-like activity and hence are a promising candidate for artificial peroxidase.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFChtLrL&md5=f3ad20d4327c286dc3fbafce611c073a
  17. 17
    Zhang, S.; Shang, B.; Yang, J.; Yan, W.; Wei, S.; Xie, Y. From VO2(B) to VO2(A) nanobelts: first hydrothermal transformation, spectroscopic study and first principles calculation. Phys. Chem. Chem. Phys. 2011, 13, 15873– 15881,  DOI: 10.1039/c1cp20838a
    Google Scholar
    17
    From VO2 (B) to VO2 (A) nanobelts: first hydrothermal transformation, spectroscopic study and first principles calculation
    Zhang, Shudong; Shang, Bo; Yang, Jinlong; Yan, Wensheng; Wei, Shiqiang; Xie, Yi
    Physical Chemistry Chemical Physics (2011), 13 (35), 15873-15881CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    The phase transition process from VO2 (B) to VO2 (A) was first obsd. through a mild hydrothermal approach, using hybrid d. functional theory (DFT) calcns. and crystallog. VO2 topol. anal. All theor. analyses reveal that VO2 (A) is a thermodynamically stable phase and has a lower formation energy compared with the metastable VO2 (B). For the first time, X-ray absorption spectroscopy (XAS) of the V L-edge and O K-edge was performed on different VO2 phases, and the differences in the electronic structure of the two polymorphic forms provide further exptl. evidence of the more stable VO2 (A). Consequently, transformation from VO2 (B) to VO2 (A) is much easier to be realized from a dynamical point of view. Notably, the transformation of VO2 (B) into VO2 (A) show the sequence VO2 (B)-high-temp. VO2 (AH) phase-low-temp. VO2 (A) phase, which was achieved by hydrothermal treatment, resp. Also, an alternative synthesis route was proposed based on the above hydrothermal transformation, and VO2 (A) was successfully prepd. via the simple one-step hydrothermal method by hydrolysis of VO(acac)2 (acac = acetylacetonate). Therefore, VO2 nanostructures with controlled phase compns. can be obtained in high yields. Through elucidating the structural evolution in the crystallog. shear mechanism, we can easily guide the design of other metal oxide nanostructures with controllable phases.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGqu7bN&md5=39cdf6a5903c9c1ccf91631e97f28cb5
  18. 18
    Zhang, S.; Li, Y.; Wu, C.; Zheng, F.; Xie, Y. Novel Flowerlike Metastable Vanadium Dioxide (B) Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries. J. Phys. Chem. C 2009, 113, 15058– 15067,  DOI: 10.1021/jp903312h
    Google Scholar
    18
    Novel Flowerlike Metastable Vanadium Dioxide (B) Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries
    Zhang, Shudong; Li, Yingmei; Wu, Changzheng; Zheng, Fei; Xie, Yi
    Journal of Physical Chemistry C (2009), 113 (33), 15058-15067CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Novel flowerlike VO2(B) micro-nanostructures assembled by single-cryst. nanosheets were synthesized via a hydrothermal route using polymer polyvinyl pyrrolidone (PVP, K30) as capping reagent. Detailed proofs indicated that the process of crystal growth was dominated by a nucleation and growth, self-assembly, and then Ostwald ripening growth mechanism. The flowerlike micro-nanostructured VO2(B) was applied as the active material in aq. Li-ion batteries which showed improved electrochem. properties with the 1st discharge capacity reaching 74.9 mA-h/g, a good value for aq. Li ion battery systems in light of previous reports (usually <65 mA-h/g). Corresponding VO2(B) nanostructures with better crystallinity were obtained by calcining the precursor of flowerlike VO2(B) structures. The post-treated flowerlike VO2(B) electrode shows better electrochem. properties with the 1st discharge capacity reaching 81.3 mA-h/g, which is higher than that of the flowerlike VO2(B) sample before annealing. The electrochem. intercalation and deintercalation properties of VO2(B) nanobelts and carambola-like VO2(B) structures with Li+ were also studied. The unique flowerlike structure plays a role in the morphol. requirement to serve as transport paths for Li ions in aq. Li ion batteries. The morphol. and crystallinity of the synthesized products had an influence on the electrochem. intercalation and deintercalation properties with Li ions.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXovFKlt74%253D&md5=853e81161aac174de5b76d5e68fc5045
  19. 19
    Walton, R. I. Subcritical solvothermal synthesis of condensed inorganic materials. Chem. Soc. Rev. 2002, 31, 230– 238,  DOI: 10.1039/b105762f
    Google Scholar
    19
    Subcritical solvothermal synthesis of condensed inorganic materials
    Walton, Richard I.
    Chemical Society Reviews (2002), 31 (4), 230-238CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. The solvothermal method has recently been extended from zeolite synthesis to the formation of condensed inorg. solids, which find uses in diverse areas due to properties such as ionic-cond., solid-state magnetism, giant magnetoresistance, low thermal expansion and ferroelectricity. This offers specific advantages over the traditional ceramic synthetic routes to inorg. solids and these are highlighted with examples from the recent literature, and the efforts focussed on detg. the formation mechanism of solids from the heterogeneous mixts. used in solvothermal procedures are discussed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XkvVCmt7o%253D&md5=ac8805ccaff49f722b4c472ee85726da
  20. 20
    Yu, W.; Li, S.; Huang, C. Phase evolution and crystal growth of VO2 nanostructures under hydrothermal reactions. RSC Adv. 2016, 6, 7113– 7120,  DOI: 10.1039/c5ra23898f
    Google Scholar
    20
    Phase evolution and crystal growth of VO2 nanostructures under hydrothermal reactions
    Yu, Weilai; Li, Shuai; Huang, Chi
    RSC Advances (2016), 6 (9), 7113-7120CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    The phase evolution and crystal growth of VO2 nanostructures against reaction time in a high-pressure V2O5-oxalic acid hydrothermal system were systematically investigated. It was found that the rather thin VO2 (B) nanobelts were first obtained, then stacked to form large belt-like structures and subsequently phase transformed into VO2 (A), based on an oriented attachment-recrystn. mechanism. The large VO2 (A) belt-like structures could further assemble into novel "snowflake" VO2 (M) microcrystals with even bigger sizes and nearly well-defined six-fold symmetry. Due to the Ostwald ripening effect regarding crystal size discrepancy, the VO2 (M) phase could further grow at the cost of the gradual dissoln. of VO2 (A) and full elimination of VO2 (B). The phase evolution from VO2 (B) first to VO2 (A) and then to VO2 (M), is actually a step-by-step thermodynamically downhill process, owing to the gradual relaxation of structural tension within the VO2 crystal lattice. Thus, our investigation, for the first time, demonstrated the feasibility of the well-known Ostwald's step rules towards the phase evolution process of VO2 and could provide unprecedented new insight to promote understanding of the synthesis and properties of vanadium oxide compds.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlvV2lsQ%253D%253D&md5=38c86bd180df72c567bacbc3a3b8057d
  21. 21
    Beidelman, B. A.; Zhang, X.; Sanchez-Lievanos, K. R.; Selino, A. V.; Matson, E. M.; Knowles, K. E. Influence of water concentration on the solvothermal synthesis of VO2(B) nanocrystals. CrystEngComm 2022, 24, 6009– 6017,  DOI: 10.1039/d2ce00813k
    Google Scholar
    21
    Influence of water concentration on the solvothermal synthesis of VO2(B) nanocrystals
    Beidelman, Brittney A.; Zhang, Xiaotian; Sanchez-Lievanos, Karla R.; Selino, Annabel V.; Matson, Ellen M.; Knowles, Kathryn E.
    CrystEngComm (2022), 24 (34), 6009-6017CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    Nanocrystals of VO2(B) have attracted significant attention for their promising performance in electrochem. energy storage applications. Phase-purity and nanocrystal morphol. are both crucial factors for the performance of these materials, but given the large no. of crystal polymorphs available to VO2, achieving simultaneous control over crystal phase and nanocrystal size is a significant synthetic challenge. This paper describes the impact of water concn. on the synthesis of VO2(B) nanocrystals via solvothermal reaction of a mol. V(IV) precursor in toluene. Using controlled, stoichiometric amts. of water (20 equiv per vanadium center) enables access to short nanorods of VO2(B) whose lengths follow a Gaussian distribution with an av. and std. deviation of 110 ± 30 nm. Decreasing the amt. of water present to two or four equiv. results in formation of VO2(A) nanocrystals and eliminating it entirely results in no reaction. Increasing the amt. of water to more than 20 equiv increases the av. length of the VO2(B) nanorods and causes the distribution in rod lengths to evolve from Gaussian to lognormal. This evolution in the size distribution is consistent with changes in a model Gaussian distribution obsd. upon simulated end-to-end oriented attachment events. These results demonstrate that control over the concn. of water is a useful strategy for tuning the morphol. and crystal phase of VO2 nanocrystals.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitV2ks73O&md5=9d7d4808dd7ab07a57b23fb3525febaa
  22. 22
    Serjeant, E. P.; Dempsey, B. Ionisation Constants of Organic Acids in Aqueous Solution; Pergamon Press: New York, New York, 1979; Vol. 23.
    Google Scholar
    There is no corresponding record for this reference.
  23. 23
    Haynes, W. H. CRC Handbook of Chemistry and Physics, 91st ed.; CRC Press Inc.: Boca Raton, FL, 2010–2011.
    Google Scholar
    There is no corresponding record for this reference.
  24. 24
    Dean, J. A. Lange’s Handbook of Chemistry, 13th ed.; McGraw-Hill Book Co: New York, NY, 1985.
    Google Scholar
    There is no corresponding record for this reference.
  25. 25
    Muckerman, J. T.; Skone, J. H.; Ning, M.; Wasada-Tsutsui, Y. Toward the accurate calculation of pKa values in water and acetonitrile. Biochim. Biophys. Acta, Bioenerg. 2013, 1827, 882– 891,  DOI: 10.1016/j.bbabio.2013.03.011
    Google Scholar
    25
    Toward the accurate calculation of pKa values in water and acetonitrile
    Muckerman, James T.; Skone, Jonathan H.; Ning, Ming; Wasada-Tsutsui, Yuko
    Biochimica et Biophysica Acta, Bioenergetics (2013), 1827 (8-9), 882-891CODEN: BBBEB4; ISSN:0005-2728. (Elsevier B. V.)
    We present a simple approach for the calcn. of accurate pKa values in water and acetonitrile based on the straightforward calcn. of the gas-phase abs. free energies of the acid and conjugate base with use of only a continuum solvation model to obtain the corresponding soln.-phase free energies. Most of the error in such an approach arises from inaccurate differential solvation free energies of the acid and conjugate base which is removed in our approach using a correction based on the realization that the gas-phase acidities have only a small systematic error relative to the dominant systematic error in the differential solvation. The methodol. is outlined in the context of the calcn. of a set of neutral acids with water as the solvent for a reasonably accurate electronic structure level of theory (DFT), basis set, and implicit solvation model. It is then applied to the comparison of results for three different hybrid d. functionals to illustrate the insensitivity to the functional. Finally, the approach is applied to the comparison of results for sets of neutral acids and protonated amine cationic acids in both aq. (water) and nonaq. (acetonitrile) solvents. The methodol. is shown to generally predict the pKa values for all the cases investigated to within 1 pH unit so long as the differential solvation error is larger than the systematic error in the gas-phase acidity calcns. Such an approach is rather general and does not have addnl. complications that would arise in a cluster-continuum method, thus giving it strength as a simple high-throughput means to calc. abs. pKa values. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmsFCjtbk%253D&md5=c6e56760baf2f86e8940fcd72bb08af1
  26. 26
    Weeks, C.; Song, Y.; Suzuki, M.; Chernova, N. A.; Zavalij, P. Y.; Whittingham, M. S. The one dimensional chain structures of vanadyl glycolate and vanadyl acetate. J. Mater. Chem. 2003, 13, 1420– 1423,  DOI: 10.1039/b208100h
    Google Scholar
    26
    The one dimensional chain structures of vanadyl glycolate and vanadyl acetate
    Weeks, Curtis; Song, Yanning; Suzuki, Masatsugu; Chernova, Natasha A.; Zavalij, Peter Y.; Whittingham, M. Stanley
    Journal of Materials Chemistry (2003), 13 (6), 1420-1423CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)
    The solvothermal reaction, at 200°, of vanadium pentoxide and lithium hydroxide in acetic acid or ethylene glycol gives vanadyl acetate and vanadyl glycolate resp. The structure of the acetate contains vanadium in octahedral coordination whereas the glycolate contains VO5 square pyramids. The VO6 octahedra in the acetate, VO(CH3COO)2, are joined through the vanadyl groups, giving a rather long V:O bond of 1.684(7) Å and a short trans V-O bond of 2.131(7) Å, and by bridging acetate groups. The vanadium atoms interact along the ···V:O···V:O··· chain giving 1-dimensional antiferromagnetic behavior. In contrast in the glycolate, the apical V:O bond is shorter, 1.58(1) Å, and the square pyramids share edges in a two up-two down fashion to give chains VO(OCH2CH2O). Magnetic susceptibility of vanadyl glycolate is consistent with an isolated spin dimers model.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvVCgsLc%253D&md5=b570fd9cea9efed13b78c01cc79cd069
  27. 27
    Casey, A. T.; Thackeray, J. R. The preparation and magnetic properties of oxovanadium(IV) acetate. Aust. J. Chem. 1969, 22, 2549– 2553,  DOI: 10.1071/ch9692549
    Google Scholar
    27
    Preparation and magnetic properties of oxovandium(IV) acetate
    Casey, Allan T.; Thackery, J. R.
    Australian Journal of Chemistry (1969), 22 (12), 2549-53CODEN: AJCHAS; ISSN:0004-9425.
    The variation of the magnetic susceptibility of oxovanadium(IV) acetate with temp. may be fitted to the Ising model of an infinite linear antifer romagnetic chain with exchange energy of -166 cm-1. On the basis of this and ir evidence, a structure for the compd. is proposed.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3cXjslWmsg%253D%253D&md5=6c034e42b8006146026c3a6ed3ef4aa6
  28. 28
    Dakternieks, D. R.; Harris, C. M.; Milham, P. J.; Morris, B. S.; Sinn, E. Magnetism and structure of polymeric oxovanadium(IV) acetate and other polymeric oxovanadium(IV) complexes. Inorg. Nucl. Chem. Lett. 1969, 5, 97– 100,  DOI: 10.1016/0020-1650(69)80177-7
    Google Scholar
    28
    Magnetism and structure of polymeric oxovanadium(IV) acetate and other polymeric oxovanadium(VI) complexes
    Dakternieks, D. R.; Harris, Clive Melville; Milham, P. J.; Morris, Benjamin S.; Sinn, Ekkehard
    Inorganic and Nuclear Chemistry Letters (1969), 5 (2), 97-100CODEN: INUCAF; ISSN:0020-1650.
    From magnetic and other evidence, it is concluded that oxovanadium(IV) acetate and other carboxylate complexes consist of polymeric structures. The V:O stretching absorption at 895 cm.-1 gives a force const. k of 5.8 millidynes/A.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXhtF2mt7s%253D&md5=a63282881ea3c3e5c17a11c0144f2955
  29. 29
    Ikekwere, P. O.; Adeniyi, A. A. Oxovanadium(IV) Complexes of Some Aromatic Carboxylic Acids. Synth. React. Inorg. Met.-Org. Chem. 1989, 19, 87– 100,  DOI: 10.1080/00945718908048053
    Google Scholar
    29
    Oxovanadium(IV) complexes of some aromatic carboxylic acids
    Ikekwere, P. O.; Adeniyi, A. A.
    Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1989), 19 (1), 87-100CODEN: SRIMCN; ISSN:0094-5714.
    VOL2.nH2O (L = BzOH and its 2-, 3- and 4-cyano-, 3-cyano-4-methyl-, 2-, 3- and 4-methyl-, 2,5- and 3,5-dimethyl-, 2,4,6-trimethyl-, 2-, 3- and 4-nitro derivs.) were prepd. and characterized by their magnetic and spectral properties. The complexes had magnetic moments much lower than the spin-only value of 1.73 μB at room temp. indicating strong magnetic interactions. Their Nujol mull spectra showed 3 main electronic absorption bands typical of tetragonally distorted octahedral oxovanadium(IV) compds. The IR vibrational spectra indicate that the carboxylate groups are bridging. The complexes are carboxylate-bridged polymers with V:O...V:O interaction.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXktFKltbs%253D&md5=ab83fb438d173fba7cf52badac767214
  30. 30
    Puri, M.; Sharma, R. D.; Verma, R. D. Trifluoroacetates of Vanadium(III) and Oxovanadium(IV) and (V) Preparation and Characterization. Synth. React. Inorg. Met.-Org. Chem. 1981, 11, 539– 546,  DOI: 10.1080/00945718108055998
    Google Scholar
    30
    Trifluoroacetates of vanadium(III) and oxovanadium(IV) and (V). Preparation and characterization
    Puri, Madhu; Sharma, R. D.; Verma, Rajendar D.
    Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1981), 11 (6), 539-46CODEN: SRIMCN; ISSN:0094-5714.
    V(O2CCF3)3 (I), VO(O2CCF3)2 (II), and VO2(O2CCF3) were prepd. by treating VCl3, VOCl2, and VOCl3, resp., with CF3CO2H. I and II were also prepd. by heating V(OAc)3 and VO(OAc)2 with CF3CO2H. The IR spectra, thermal degrdn., magnetic susceptibilities, and reflectance spectra of the compds. were detd.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38Xht1aitLs%253D&md5=dfdabce00d2634d5c7519bd8d3f3a35d
  31. 31
    Lorenzotti, A.; Leonesi, D.; Cingolani, A.; Di Bernardo, P. Vanadyl(IV)─Acetate complexes in aqueous solution. J. Inorg. Nucl. Chem. 1981, 43, 737– 738,  DOI: 10.1016/0022-1902(81)80213-8
    Google Scholar
    31
    Vanadyl(IV)-acetate complexes in aqueous solution
    Lorenzotti, Adriana; Leonesi, Dante; Cingolani, Augusto; Di Bernardo, Plinio
    Journal of Inorganic and Nuclear Chemistry (1981), 43 (4), 737-8CODEN: JINCAO; ISSN:0022-1902.
    The formation of vanadyl(IV) complexes with acetates were studied by potentiometric titrn. methods; the stability consts. of mononuclear complexes, [VO(CH3COO)]+ and [VO(CH3COO)2], were calcd. to be 72.2 and 12.6 M-1, resp., in 1M aq. perchlorate at 25°. A comparison was made with the literature values for the corresponding neptunyl(IV) complexes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXktlWht78%253D&md5=d53355c3f23bd1243e57ac91ab797f5b
  32. 32
    Di Bernardo, P.; Tomat, G.; Zanonato, P.; Portanova, R.; Tolazzi, M. Thermodynamics of vanadyl(IV)─carboxylate complex formation in aqueous solution. Inorg. Chim. Acta 1988, 145, 285– 288,  DOI: 10.1016/s0020-1693(00)83971-7
    Google Scholar
    32
    Thermodynamics of vanadyl(IV)-carboxylate complex formation in aqueous solution
    Di Bernardo, Plinio; Tomat, Giuliana; Zanonato, Pierluigi; Portanova, Roberto; Tolazzi, Marilena
    Inorganica Chimica Acta (1988), 145 (2), 285-8CODEN: ICHAA3; ISSN:0020-1693.
    The stability consts. and the heats of formation of vanadyl(IV)-acetate, -glycolate, and -glycine complexes were detd. in aq. soln. by potentiometric and calorimetric measurements. In the pH range where the protolytic equil. of VO2+ is negligible, acetate forms 2 mononuclear complexes, glycolate 3, while glycine reacts in its zwitterionic form. The stabilities of the glycolate complexes are considerably higher than the acetate complexes, in spite of its lower basicity, indicating that complex formation involves the coordination of the OH group. The enthalpy changes are pos. except for glycolate where a small neg. value is found. For all systems, the entropy changes are pos. and therefore favorable to the complex formation.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXltFOjur8%253D&md5=f08fc3a701e03e24092175d6e4861700
  33. 33
    Mehio, N.; Ivanov, A. S.; Ladshaw, A. P.; Dai, S.; Bryantsev, V. S. Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents. Ind. Eng. Chem. Res. 2016, 55, 4231– 4240,  DOI: 10.1021/acs.iecr.5b03398
    Google Scholar
    33
    Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents
    Mehio, Nada; Ivanov, Alexander S.; Ladshaw, Austin P.; Dai, Sheng; Bryantsev, Vyacheslav S.
    Industrial & Engineering Chemistry Research (2016), 55 (15), 4231-4240CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
    Poly(acrylamidoxime) fibers are the current state-of-the-art adsorbent for mining uranium from seawater. However, the competition between uranyl (UO22+) and vanadium ions poses a challenge to mining on the industrial scale. In this work, we employ d. functional theory and coupled-cluster methods in the restricted formalism to investigate potential binding motifs of the oxovanadium(IV) ion (VO2+) with the formamidoximate ligand. Consistent with exptl. extended X-ray absorption fine structure data, the hydrated six-coordinate complex is predicted to be preferred over the hydrated five-coordinate complex. Our investigation of formamidoximate-VO2+ complexes universally identified the most stable binding motif formed by chelating a tautomerically rearranged imino hydroxylamine via the imino nitrogen and hydroxylamine oxygen. The alternative binding motifs for amidoxime chelation via a nonrearranged tautomer and η2 coordination are found to be ∼11 kcal/mol less stable. Natural bond orbital anal. was performed to understand the nature of the interactions in the VO2+ complexes. The difference in the most stable VO2+ and UO22+ binding conformation has important implications for the design of more selective UO22+ ligands.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVyit7jL&md5=ffaf2049955182832f1549baa63c4f99
  34. 34
    Winkler, J. R.; Gray, H. B. Electronic Structures of Oxo-Metal Ions. In Molecular Electronic Structures of Transition Metal Complexes I. Structure and Bonding; Mingos, D. M. P., Day, P., Dahl, J. P., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2012; vol. 142, pp 17– 28.
    Google Scholar
    There is no corresponding record for this reference.
  35. 35
    Krakowiak, J.; Lundberg, D.; Persson, I. A Coordination Chemistry Study of Hydrated and Solvated Cationic Vanadium Ions in Oxidation States +III, +IV, and +V in Solution and Solid State. Inorg. Chem. 2012, 51, 9598– 9609,  DOI: 10.1021/ic300202f
    Google Scholar
    35
    A Coordination Chemistry Study of Hydrated and Solvated Cationic Vanadium Ions in Oxidation States +III, +IV, and +V in Solution and Solid State
    Krakowiak, Joanna; Lundberg, Daniel; Persson, Ingmar
    Inorganic Chemistry (2012), 51 (18), 9598-9609CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
    The coordination chem. of hydrated and solvated vanadium(III), oxovanadium(IV), and dioxovanadium(V) ions in the oxygen-donor solvents water, DMSO , and N,N'-dimethylpropyleneurea (DMPU) was studied in soln. by extended x-ray absorption fine structure (EXAFS) and large-angle X-ray scattering (LAXS) and in the solid state by single-crystal X-ray diffraction and EXAFS. The hydrated vanadium(III) ion has a regular octahedral configuration with a mean V-O bond distance of 1.99 Å. In the hydrated and DMSO-solvated oxovanadium(IV) ions, vanadium binds strongly to an oxo group at ∼1.6 Å. The solvent mol. trans to the oxo group is very weakly bound, at ∼2.2 Å, while the remaining four solvent mols., with a mean V-O bond distance of 2.0 Å, form a plane slightly below the vanadium atom; the mean O=V-Operp bond angle is ∼98°. In the DMPU-solvated oxovanadium(IV) ion, the space-demanding properties of the DMPU mol. leave no solvent mol. in the trans position to the oxo group, which reduces the coordination no. to 5. The O=V-O bond angle is consequently much larger, 107°, and the mean V=O and V-O bond distances decrease to 1.58 and 1.97 Å, resp. The hydrated and DMSO-solvated dioxovanadium(V) ions display a very distorted octahedral configuration with the oxo groups in the cis position with a mean V=O bond distance of 1.6 Å and a O=V=O bond angle of ∼105°. The solvent mols. trans to the oxo groups are weakly bound, at ∼2.2 Å, while the remaining two have bond distances of 2.02 Å. The exptl. studies of the coordination chem. of hydrated and solvated vanadium(III,IV,V) ions are complemented by summarizing previously reported crystal structures to yield a comprehensive description of the coordination chem. of vanadium with oxygen-donor ligands.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlSks7nL&md5=e69f2a1d2daac25be6f4a51cedebef0b
  36. 36
    Rumble, J. R. CRC Handbook of Chemistry and Physics, Internet Edition 2018, 99th ed.; CRC Press/Taylor & Francis: Boca Raton, FL, 2018.
    Google Scholar
    There is no corresponding record for this reference.
  37. 37
    Guo, Y.; Surblys, D.; Matsubara, H.; Kawagoe, Y.; Ohara, T. Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface. J. Phys. Chem. C 2020, 124, 27558– 27570,  DOI: 10.1021/acs.jpcc.0c08940
    Google Scholar
    37
    Molecular dynamics study on effect of long-chain surfactant adsorption on interfacial heat transfer between polymer liquid and silica surface
    Guo, Yuting; Surblys, Donatas; Matsubara, Hiroki; Kawagoe, Yoshiaki; Ohara, Taku
    Journal of Physical Chemistry C (2020), 124 (50), 27558-27570CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    The addn. of surfactants to polymer-based thermal interface materials applied to improve the heat dissipation efficiency of chip surfaces in contact has attracted attention for the microelectronic processing technol. In the present study, the mechanism by which a long-chain surfactant affects heat transfer across the interface between solid surface and polymer liq. was investigated by non-equil. mol. dynamics simulation. We constructed a system where tetracosane was used as a solvent and contained alc. mols. as a surfactant, and they were placed between two flat silica surfaces under a thermal gradient. The effect of the hydrophilicity of silica surface, the concn. of the surfactant, and chain length of the surfactant on silica-liq. interfacial thermal resistance Rb were examd. Alc. surfactant mols. preferred to adsorb onto the hydrophilic silica (Si-OH) surface due to hydrogen bonding between alc. and silanol hydroxyl groups. It was found that Rb reduced not only with the adsorption amt. of alc. mols. but also with the chain length of alc. The van der Waals interaction contribution was dominant for solid-liq. and liq.-liq. heat conduction near the interface. The hydroxyl terminals of alc. mols. were vertically adsorbed onto the Si-OH surface due to hydrogen bonds, which produced a heat path from silanols to the hydroxyl groups of alc. Furthermore, heat was also exchanged between alc. hydroxyl and alkyl groups via intramol. interaction and between the alc. alkyl groups and nearby solvent mols. via van der Waals (vdW) intermol. interaction. This resulted in an efficient heat path from solid surface silanols to liq. bulk. As the alc. chain length increased without changing the no. of adsorbed alc. mols., the heat transfer through this heat path increased, which led to a decrease in Rb. These results provided insight toward the guiding principle for the mol. design of complex surfactants to enhance the interfacial heat transfer.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisV2hu73K&md5=b84d8894327b9cc141f818c12772aef2
  38. 38
    Uchaker, E.; Gu, M.; Zhou, N.; Li, Y.; Wang, C.; Cao, G. Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano-Structured Electrode Materials: Vanadium Oxide Mesocrystals. Small 2013, 9, 3880– 3886,  DOI: 10.1002/smll.201203187
    Google Scholar
    38
    Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano-Structured Electrode Materials: Vanadium Oxide Mesocrystals
    Uchaker, Evan; Gu, Meng; Zhou, Nan; Li, Yanwei; Wang, Chongmin; Cao, Guozhong
    Small (2013), 9 (22), 3880-3886CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
    An additive and template free process is developed for the facile synthesis of VO2(B) mesocrystals via the solvothermal reaction of oxalic acid and vanadium pentoxide. The six-armed star architectures are composed of stacked nanosheets homoepitaxially oriented along the [100] crystallog. register with respect to one another, as confirmed by means of selected area electron diffraction and electron microscopy. It is proposed that the mesocrystal formation mechanism proceeds through classical as well as non-classical crystn. processes, and is possibly facilitated or promoted by the presence of a reducing/chelating agent. The synthesized VO2(B) mesocrystals are tested as a cathodic electrode material for lithium-ion batteries, and show good capacity at discharge rates ranging from 150-1500 mA g-1 and a cyclic stability of 195 mA h g-1 over fifty cycles. The superb electrochem. performance of the VO2(B) mesocrystals is attributed to the porous and oriented superstructure that ensures large surface area for redox reaction and short diffusion distances. The mesocryst. structure ensures that all the surfaces are in intimate contact with the electrolyte, and that lithium-ion intercalation occurs uniformly throughout the entire electrode. The exposed (100) facets also lead to fast lithium intercalation, and the homoepitaxial stacking of nanosheets offers a strong inner-sheet binding force that leads to better accommodation of the strain induced during cycling, thus circumventing the capacity fading issues typically assocd. with VO2(B) electrodes.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntF2ksLk%253D&md5=6c44f9f3abed96d1ede41c768401b5a9
  39. 39
    Zeininger, L.; Portilla, L.; Halik, M.; Hirsch, A. Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles. Chem.─Eur. J. 2016, 22, 13506– 13512,  DOI: 10.1002/chem.201601920
    Google Scholar
    39
    Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles
    Zeininger, Lukas; Portilla, Luis; Halik, Marcus; Hirsch, Andreas
    Chemistry - A European Journal (2016), 22 (38), 13506-13512CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The adsorption, desorption, co-adsorption, and exchange of phosphonic acid, carboxylic acid, and catechol derivs. on the surface of titanium oxide (anatase) nanoparticles are investigated. Thermogravimetric anal. provides a facile and fast-track quant. detn. of the wet-chem. monolayer adsorption consts. and grafting densities of ten adsorbates, all under neutral pH conditions. This characterization protocol allows straightforward quantification of the relevant thermodn. data of ligand adsorption and a comparison of ligand adsorption strengths. The reported procedure is proposed as a universal tool and it should be applicable to many other colloidal metal oxide materials. Moreover, the detd. values for the adsorption consts. and the monolayer grafting densities provide a toolbox for the assessment of the adsorbates' behavior in desorption, exchange, and co-adsorption equil. This versatile evaluation procedure will help to identify optimal monolayer-surface combinations and to evaluate crit. parameters, such as monolayer robustness, ligand exchange rates, or targeted mixed assembly of functionalities.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1WmtLbL&md5=9c49d50096a1908a791fdd7cc4bf7991
  40. 40
    De Roo, J.; Justo, Y.; De Keukeleere, K.; Van den Broeck, F.; Martins, J. C.; Van Driessche, I.; Hens, Z. Carboxylic-Acid-Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif. Angew. Chem., Int. Ed. 2015, 54, 6488– 6491,  DOI: 10.1002/anie.201500965
    Google Scholar
    40
    Carboxylic-Acid-Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif
    De Roo, Jonathan; Justo, Yolanda; De Keukeleere, Katrien; Van den Broeck, Freya; Martins, Jose C.; Van Driessche, Isabel; Hens, Zeger
    Angewandte Chemie, International Edition (2015), 54 (22), 6488-6491CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Studying sterically stabilized HfO2 and ZrO2 NCs using 1H soln. NMR and IR spectroscopy as well as elemental anal., this paper demonstrates the reversible exchange of initial oleic acid ligands for octylamine and self-adsorption of oleic acid at NC surfaces. Both processes are incompatible with an X-type binding motif of carboxylic acids as reported for sulfide and selenide NCs. This behavior stems from the dissociative adsorption of carboxylic acids at the oxide surface. Both proton and carboxylate moieties must be regarded as X-type ligands yielding a combined X2 binding motif that allows for self-adsorption and exchange for L-type ligands.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmtlGqsr4%253D&md5=a55ec98a8761a97e2f1900720b8f7aa5
  41. 41
    Calatayud, D. G.; Rodríguez, M.; Jardiel, T. Controlling the morphology of TiO2 nanocrystals with different capping agents. Bol. Soc. Esp. Ceram. Vidrio 2015, 54, 159– 165,  DOI: 10.1016/j.bsecv.2015.07.001
    Google Scholar
    41
    Controlling the morphology of TiO2 nanocrystals with different capping agents
    Calatayud, David G.; Rodriguez, Monica; Jardiel, Teresa
    Boletin de la Sociedad Espanola de Ceramica y Vidrio (2015), 54 (4), 159-165CODEN: BSCVB9; ISSN:0366-3175. (Sociedad Espanola de Ceramica y Vidrio)
    This paper provides direct evidence to support the role of capping agents in controlling the evolution of TiO2 seeds into nanocrystals with a specific shape. Starting with Ti(OBut)4 and using oleid acid, oleylamine, dioleamide, 11-aminoundecanoic acid, arginine, trifluroacetic acid or HF as capping agents, mainly TiO2 truncated octahedrons enclosed by {1 0 1} and {0 0 1} facets were obtained. We could also selectively obtain square, rods and rounded rhombic-shaped nanoparticles by growing of {0 1 0} facets by adding oleic acid and oleylamine in ratio 6:4, resp., while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, a versatile approach to controlling the shape of metal oxide nanocrystals.
    >> More from SciFinder ®
    https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1Snu77O&md5=691f7e4efcd1878d15164aa9c21d983d

Cited By

Click to copy section linkSection link copied!

This article is cited by 1 publications.

  1. Emma J. Endres, Jeremy R. Bairan Espano, Alexandra Koziel, Antony R. Peng, Andrey A. Shults, Janet E. Macdonald. Controlling Phase in Colloidal Synthesis. ACS Nanoscience Au 2024, 4 (3) , 158-175. https://doi.org/10.1021/acsnanoscienceau.3c00057
Download PDF
Go to ACS Nanoscience Au
Get e-Alerts
Get e-Alerts

ACS Nanoscience Au

Cite this: ACS Nanosci. Au 2023, 3, 5, 381–388
Click to copy citationCitation copied!
https://doi.org/10.1021/acsnanoscienceau.3c00014
Published June 22, 2023

Copyright © 2023 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Article Views

1764

Altmetric

-

Citations

1
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Plot of crystal phases obtained from solvothermal reactions of 0.25 mmol VO(acac)2 in toluene with 4 equiv (1 mmol) of carboxylic acid and varying water concentrations (2–100 equiv). Crystal structures were determined using powder X-ray diffraction, and the data can be found in the Supporting Information (Figures S1–S6).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. (left) Powder X-ray diffraction spectra of products obtained from solvothermal reactions containing 1 equiv (0.25 mmol) VO(acac)2, 4 equiv (1 mmol) acid, 4 equiv (1 mmol) water, and 10 mL of toluene. The powder X-ray diffraction spectrum of the product obtained from a reaction containing 4 equiv of lauric acid and 120 equiv (30 mmol) of water is included for reference as an example of a VO2(B) nanocrystal product. Reference powder patterns for VO2(A) (JCPDS 00-042-0876, red) and VO2(B) (JCPDS 01-081-2392, black) are also included. (right) Crystal structures of the confirmed products include VO(4-nitrobenzoate)2 (top), VO(benzoate)2 (middle), and VO(acetate)2 (bottom).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. Plots of the crystal phase of VO2 nanocrystals obtained from reaction mixtures containing (A) various concentrations of VO(acac)2 and water with a constant concentration of trifluoroacetic acid, and (B) various concentrations of trifluoroacetic acid and water with a constant concentration of VO(acac)2. The amounts of reagents used in each of these reactions are tabulated in Table S3, and the powder X-ray diffraction spectra used to construct these plots are shown in the Supporting Information (Figures S9–S12).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. (A) Powder X-ray diffraction spectra of nanocrystals obtained from solvothermal reactions of VO2(B) nanocrystals in toluene with 20 equiv of water and 4 equiv of trifluoroacetic acid at 230 °C demonstrate the transformation from VO2(B) to VO2(A) after 120 h of reaction time. The black dotted rectangles highlight the pairs of diffraction peaks in VO2(B) that coalesce to form the peaks associated with diffraction of the (110) and (220) planes of VO2(A). (B,C) TEM images of (B) the VO2(B) nanocrystals used as the starting material and (C) the VO2(A) nanocrystals obtained after reacting the nanocrystals shown in B in toluene with 20 equiv of water and 4 equiv of trifluoroacetic acid at 230 °C for 120 h. The scale bars correspond to 200 nm.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. SEM images of reactions with 1 equiv (0.25 mmol) VO(acac)2, 60 equiv (15 mmol) water, and 4 equiv (1 mmol) of (A) no ligand, (B) lauric acid, (C) acetic acid, (D) benzoic acid, (E) 4-nitrobenzoic acid, and (F) trifluoroacetic acid. Each image contains a scale bar corresponding to 1 μm.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 41 other publications.

    1. 1
      Wu, C.; Feng, F.; Xie, Y. Design of vanadium oxide structures with controllable electrical properties for energy applications. Chem. Soc. Rev. 2013, 42, 5157– 5183,  DOI: 10.1039/c3cs35508j
      1
      Design of vanadium oxide structures with controllable electrical properties for energy applications
      Wu, Changzheng; Feng, Feng; Xie, Yi
      Chemical Society Reviews (2013), 42 (12), 5157-5183CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. The elec. properties of inorg. materials has been a long-standing pursued research topic, and successfully controlling the elec. property of an inorg. material has attracted significant attention for a wide range of energy-related applications, covering energy storage, energy conversion and energy utilization. During the few past decades, vanadium oxides have been studied to gain a clear picture of how microstructural characteristics generating the e-e correlations influence the electronic structure of a material, through which the charge concn., elec. cond. as well as the metal-insulator transition (MIT), etc., can be precisely controlled, giving promising signs for constructing energy-related devices. In this review, we present an extensive review of the engineering of the microstructures of vanadium oxides with control of their elec. properties, and with attempts to rationally construct energy-related devices, such as aq. lithium ion batteries, supercapacitors for energy storage, and thermoelec. generators for energy conversion. Furthermore, the MIT performance of vanadium oxides has also seen tremendous advantages for the applications of "smart windows" and magnetocaloric refrigerators for energy utilization. Collectively, progresses to date suggest that in vanadium oxide systems, the elec. properties, including elec. cond., carrier concns., and the MIT performance, were all strongly dependent on the microstructural characteristics at the at. scale, which have presented extensive promising energy applications covering energy storage, energy conversion and energy utilization.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXot1ersr8%253D&md5=ddc30e955f7e900d2efa35cb65c64809
    2. 2
      Li, M.; Magdassi, S.; Gao, Y.; Long, Y. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows. Small 2017, 13, 1701147,  DOI: 10.1002/smll.201701147
      There is no corresponding record for this reference.
    3. 3
      Zhang, Y.; Fan, M.; Liu, X.; Xie, G.; Li, H.; Huang, C. Synthesis of VO2(A) nanobelts by the transformation of VO2(B) under the hydrothermal treatment and its optical switching properties. Solid State Commun. 2012, 152, 253– 256,  DOI: 10.1016/j.ssc.2011.11.036
      3
      Synthesis of VO2(A) nanobelts by the transformation of VO2(B) under the hydrothermal treatment and its optical switching properties
      Zhang, Yifu; Fan, Meijuan; Liu, Xinghai; Xie, Guangyong; Li, Houbin; Huang, Chi
      Solid State Communications (2012), 152 (4), 253-256CODEN: SSCOA4; ISSN:0038-1098. (Elsevier Ltd.)
      VO2(A) nanobelts had been successfully synthesized by the transformation of VO2(B) using H2O as the solvent under the hydrothermal approach at 280 °C for 48 h. Some parameters, such as the reaction temp. and time, had been briefly discussed to reveal the transition from VO2(B) to VO2(A). It was found that H2O played a crucial role in the transition from VO2(B) to VO2(A). The phase transition of VO2(A) nanobelts was at 162 °C. The optical switching properties of VO2(A) were studied by the variable-temp. IR spectra for the first time. In addn., VO2(A) nanobelts were calcined at 700 °C for 2 h under a high purity Ar (99.999%) atm. to obtain VO2(M) which exhibited a strong crystallog. transition at around 65 °C.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpsFOjsA%253D%253D&md5=e99134ae24630224d8694450f8f372fd
    4. 4
      Liu, P.; Zhu, K.; Gao, Y.; Wu, Q.; Liu, J.; Qiu, J.; Gu, Q.; Zheng, H. Ultra-long VO2(A) nanorods using the high-temperature mixing method under hydrothermal conditions: synthesis, evolution and thermochromic properties. CrystEngComm 2013, 15, 2753– 2760,  DOI: 10.1039/c3ce27085h
      4
      Ultra-long VO2 (A) nanorods using the high-temperature mixing method under hydrothermal conditions: synthesis, evolution and thermochromic properties
      Liu, Pengcheng; Zhu, Kongjun; Gao, Yanfeng; Wu, Qingliu; Liu, Jinsong; Qiu, Jinhao; Gu, Qilin; Zheng, Hongjuan
      CrystEngComm (2013), 15 (14), 2753-2760CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      Well-crystd., ultra-long VO2 (A) nanorods were prepd. using a facile high-temp. mixing method (HTMM) under hydrothermal conditions. The as-obtained products were characterized by x-ray diffraction, field-emission SEM, transmission electron microscopy, XPS, UV-Vis-NIR, DSC, and FTIR. The effect of W doping on the phase-transition properties of VO2(A) was also studied. The optimal condition of VO2(A) using the HTMM is hydrothermal treatment at 240° for 48 h with a 3:1 molar ratio of the reducing agent to the vanadium source. The reason why the polymorphic forms of VO2 show different colors is that the light in the visible region reflected by the samples is different. The phase-transition temp. of the pure VO2 (A) is 154.75°, which is significantly lower than the 162 °C reported previously. When a small amt. of W is doped, VO2(A) will be transformed into other polymorphic forms, which indicates that the crystal structure of VO2(A) is highly sensitive to limited doping. Importantly, the as-obtained pure VO2(A) shows good thermochromic properties and optical-switching characters. A crystal growth mechanism for VO2(A), oriented-attachment-exfoliation-recrystn.-oriented-attachment, is proposed and described in detail.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjslKgs78%253D&md5=24b8f349248f47c43ba3f776251a7173
    5. 5
      Subba Reddy, C. V.; Walker, E. H., Jr.; Wicker, S. A., Sr.; Williams, Q. L.; Kalluru, R. R. Synthesis of VO2(B) nanorods for Li battery application. Curr. Appl. Phys. 2009, 9, 1195– 1198,  DOI: 10.1016/j.cap.2009.01.012
      There is no corresponding record for this reference.
    6. 6
      Soltane, L.; Sediri, F. Rod-like nanocrystalline B-VO2: Hydrothermal synthesis, characterization and electrochemical properties. Mater. Res. Bull. 2014, 53, 79– 83,  DOI: 10.1016/j.materresbull.2014.01.046
      6
      Rod-like nanocrystalline B-VO2: Hydrothermal synthesis, characterization and electrochemical properties
      Soltane, L.; Sediri, F.
      Materials Research Bulletin (2014), 53 (), 79-83CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
      Rod-like nanocryst. VO2(B) has been successfully synthesized via a simple hydrothermal process by using V2O5 as vanadium source and 4-butylaniline H3C-(CH2)3-(C6H4)-NH2 as reducing and structure directing agent. The compds. were analyzed through X-ray diffraction (XRD), SEM (SEM), Fourier transform IR spectroscopy (FTIR), Raman spectroscopy and UV-visible spectroscopy. The VO2(B) nanorods are up to several micrometers in length and about 80 nm in thickness with a large optical band gap of ∼2.709 eV. Thin films of VO2(B) nanorods deposited on ITO substrates were electrochem. characterized by cyclic voltammetry. The voltammograms show reversible redox behavior with charge-discharge cycling process corresponding to the reversible lithium intercalation/deintercalation into the crystal lattice. The av. coulombic efficiency to this redox processes is upper 98% during the electrochem. measurements.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmsFCmtLk%253D&md5=8b9e591eaf47af46b4d92ff3dd4afc0a
    7. 7
      Yin, H.; Yu, K.; Zhang, Z.; Zhu, Z. Morphology-control of VO2(B) nanostructures in hydrothermal synthesis and their field emission properties. Appl. Surf. Sci. 2011, 257, 8840– 8845,  DOI: 10.1016/j.apsusc.2011.04.079
      7
      Morphology-control of VO2 (B) nanostructures in hydrothermal synthesis and their field emission properties
      Yin, Haihong; Yu, Ke; Zhang, Zhengli; Zhu, Ziqiang
      Applied Surface Science (2011), 257 (21), 8840-8845CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
      VO2 (B) nanostructures were synthesized via a facile hydrothermal process using V2O5 as source material and oxalic acid as reductant. Three nanostructures of nanorods, nanocarambolas and nanobundles were found existing in the products, and a continuous changing of morphol. was found in the synthesis process, during which the proportion of these three types of nanostructures can be adjusted by altering the concns. of oxalic acid. The microstructures were evaluated using X-ray diffraction, SEM and TEM. Field emission (FE) properties of these three types of nanostructures showed that the nanobundles have the best field emission performance with a turn-on field of ∼1.4 V/μm and a threshold field of ∼5.38 V/μm. These characteristics make VO2 (B) nanostructures a competitive cathode material in field emission devices.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXos1egsr0%253D&md5=8e63026251f96878a79d78084f070814
    8. 8
      Ganganagappa, N.; Siddaramanna, A. One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery. Mater. Charact. 2012, 68, 58– 62,  DOI: 10.1016/j.matchar.2012.03.010
      8
      One step synthesis of monoclinic VO2 (B) bundles of nanorods: Cathode for Li ion battery
      Ganganagappa, Nagaraju; Siddaramanna, Ashoka
      Materials Characterization (2012), 68 (), 58-62CODEN: MACHEX; ISSN:1044-5803. (Elsevier)
      One of the metastable phases of vanadium dioxide, VO2(B) bundles of nanorods and microspheres have been synthesized through a simple hydrothermal method by dispersing V2O5 in aq. quinol. The obtained products were characterized by X-ray diffraction (XRD), Fourier transform IR (FTIR) spectroscopy, SEM (SEM) and electrochem. discharge-charge test for lithium battery. It was found that the morphologies of the obtained VO2(B) can be tuned by manipulating the relative amt. of quinol. The electrochem. test found that the bundles of nanorods exhibit an initial discharge capacity of 171 mAh g- 1 and its almost stabilized capacity was reached to 108 mAh g- 1 after 47 cycles at a c.d. of 0.1 mA g- 1. The formation mechanism of the VO2(B) bundles of nanorods and microspheres was also discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XntFyksLY%253D&md5=1aa9780a7480b9a28d9680b529a2636e
    9. 9
      Zhang, Y. VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties. Mater. Sci.-Pol. 2016, 34, 169– 176,  DOI: 10.1515/msp-2016-0023
      9
      VO2(B) conversion to VO2(A) and VO2(M) and their oxidation resistance and optical switching properties
      Zhang, Yifu
      Materials Science-Poland (2016), 34 (1), 169-176CODEN: MSACDV; ISSN:2083-134X. (Walter de Gruyter GmbH)
      Vanadium dioxide VO2 has been paid in recent years increasing attention because of its various applications, however, its oxidn. resistance properties in air atm. have rarely been reported. Herein, VO2(B) nanobelts were transformed into VO2(A) and VO2(M) nanobelts by hydrothermal route and calcination treatment, resp. Then, we comparatively studied the oxidn. resistance properties of VO2(B), VO2(A) and VO2(M) nanobelts in air atm. by thermo-gravimetric anal. and DTA (TGA/DTA). It was found that the nanobelts had good thermal stability and oxidn. resistance below 341°C, 408°C and 465°C in air, resp., indicating that they were stable in air at room temp. The fierce oxidn. of the nanobelts occurred at 426, 507 and 645°C, resp. The results showed that the VO2(M) nanobelts had the best thermal stability and oxidn. resistance among the others. Furthermore, the phase transition temps. and optical switching properties of VO2(A) and VO2(M) were studied by differential scanning calorimetry (DSC) and variable temp. IR spectra. It was found that the VO2(A) and VO2(M) nanobelts had outstanding thermochromic character and optical switching properties.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XnvFWgtLg%253D&md5=824fffaabc1ee70900b734e7cb8ed72d
    10. 10
      Sediri, F.; Gharbi, N. Controlled hydrothermal synthesis of VO2(B) nanobelts. Mater. Lett. 2009, 63, 15– 18,  DOI: 10.1016/j.matlet.2008.08.022
      There is no corresponding record for this reference.
    11. 11
      Wang, Q.; Xu, J.; Zhang, W.; Mao, M.; Wei, Z.; Wang, L.; Cui, C.; Zhu, Y.; Ma, J. Research progress on vanadium-based cathode materials for sodium ion batteries. J. Mater. Chem. A 2018, 6, 8815– 8838,  DOI: 10.1039/c8ta01627e
      11
      Research progress on vanadium-based cathode materials for sodium ion batteries
      Wang, Qinghong; Xu, Jiantie; Zhang, Wenchao; Mao, Minglei; Wei, Zengxi; Wang, Lei; Cui, Chunyu; Zhu, Yuxuan; Ma, Jianmin
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2018), 6 (19), 8815-8838CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      A review is presented. Sodium ion batteries (SIBs) have attracted increasing attention as one of the most promising candidates for cost-effective, high-energy rechargeable batteries. Owing to their high theor. capacity and energy d., and rich electrochem. interaction with Na+ (V2+-V5+), a large no. of vanadium(V)-based cathode materials, including vanadium oxides (e.g., V2O5 and VO2), vanadium bronzes (e.g., NaxVO2, NaV3O8, NaV6O15 and δ-NH4V4O10), V-based phosphates (e.g., Na3V2(PO4)3, VOPO4, NaVOPO4, Na7V3(P2O7)4 and Na2(VO)P2O7) and F-contg. V-based polyanions (e.g., NaVPO4F, Na3V2(PO4)2F3 and Na3(VOx)2(PO4)2F3-2x), have been explored for SIBs. In this review, we mainly summarize the basic structures, modified/optimized structures, synthetic methods and morphol. control of V-based cathode materials for SIBs. Addnl., major drawbacks, emerging challenges and some perspectives on the development of V-based cathode materials for SIBs are also discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXntlCnsrs%253D&md5=32772400483c5ac72c28bae062b824d9
    12. 12
      Zhang, L.; Yao, J.; Guo, Y.; Xia, F.; Cui, Y.; Liu, B.; Gao, Y. VO2(A) Nanorods: One-pot Synthesis, Formation Mechanism and Thermal Transformation to VO2(M). Ceram. Int. 2018, 44, 19301– 19306,  DOI: 10.1016/j.ceramint.2018.07.157
      12
      VO2(A) nanorods: One-pot synthesis, formation mechanism and thermal transformation to VO2(M)
      Zhang, Liangmiao; Yao, Jianing; Guo, Yunfeng; Xia, Fang; Cui, Yuanyuan; Liu, Bin; Gao, Yanfeng
      Ceramics International (2018), 44 (16), 19301-19306CODEN: CINNDH; ISSN:0272-8842. (Elsevier Ltd.)
      The monoclinic VO2(M) has promising applications in intelligent devices but its prepn. still requires improvement to permit cost-effective mass prodn. In this work, we report a 2-stage approach for producing VO2(M) nanorods by (1) hydrothermal redn. of vanadium pentoxide by sodium bisulfate at 220°C to form VO2(A), and (2) subsequent thermal activated phase transformation of VO2(A) to VO2(M) at 350-450°C in vacuum. The obtained VO2(M) nanorods showed a reversible phase transition temp. at about 62.5°C and a narrow thermal hysteresis width of 10°C. The mechanism of the hydrothermal redn. was studied by combined ex situ microscopic and diffraction characterization of cooled samples as well as in situ PXRD expts., in which the hydrothermal synthesis was monitored in real time by time-resolved diffraction datasets. It was found that the hydrothermal synthesis of VO2(A) is a 4-step process: (1) redn. of V2O5 to form VO2(B) nanoparticles, (2) oriented attachment of VO2(B) nanoparticles along the [110] direction, (3) formation of VO2(B) nanorods as a results of oriented attachments, and (4) hydrothermal transformation of the metastable intermediate VO2(B) nanorods to VO2(A) nanorods. This clear understanding of the mechanism will help the further optimization of synthesis temp. and time for prepg. VO2(A). This method provides a low temp. thermal treatment alternative and hence helps the redn. of cost for the prodn. of VO2(M), bring the mass application of VO2(M) one step closer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhsVartb3L&md5=b980416b5b434be3ddf18b028717cc1c
    13. 13
      Popuri, S.; Artemenko, A.; Labrugere, C.; Miclau, M.; Villesuzanne, A.; Pollet, M. VO2(A) Reinvestigation of crystal structure, phase transition and crystal growth mechanisms. J. Solid State Chem. 2014, 213, 79– 86,  DOI: 10.1016/j.jssc.2014.01.037
      There is no corresponding record for this reference.
    14. 14
      Ji, S.; Zhang, F.; Jin, P. Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure. J. Solid State Chem. 2011, 184, 2285– 2292,  DOI: 10.1016/j.jssc.2011.06.029
      14
      Selective formation of VO2(A) or VO2(R) polymorph by controlling the hydrothermal pressure
      Ji, Shidong; Zhang, Feng; Jin, Ping
      Journal of Solid State Chemistry (2011), 184 (8), 2285-2292CODEN: JSSCBI; ISSN:0022-4596. (Elsevier B.V.)
      VO2(A) usually occurs during the prepn. of VO2 polymorphs. This leads to an ambiguous understanding of the transformation between VO2 polymorphs. The calcn. of the ground state energies for different VO2 polymorphs indicated that there is only a small energy gap between VO2(A) and VO2(R), which suggests that the transformation from VO2(A) to VO2(R) should be pressure sensitive. This hypothesis was verified during the synthesizing of VO2 polymorphs by reducing V2O5 with oxalic acid through hydrothermal treatment process. Selective formation of pure phase VO2(A) or VO2(R) was achieved by controlling the hydrothermal pressure through varying the filling ratio at 270°. It was found that a filling ratio >0.5 favors the formation of pure VO2(R) while a filling ratio ≤0.4 results in the formation of VO2(A). Based on our expts., VO2(B) nanobelts always formed first and then transformed to VO2(A) by an assembling process at increased temp. or extended reaction time. Under further higher pressure, the VO2(A) transformed spontaneously to VO2(R) initialized from the vol. shrinkage due to the formation of denser VO2(R).
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXpt1Cms7Y%253D&md5=7be35329c5ffd268cc056cfdda465286
    15. 15
      Cheng, X. H.; Xu, H. F.; Wang, Z. Z.; Zhu, K. R.; Li, G.; Jin, S. Synthesis, characterization and formation mechanism of metastable phase VO2(A) nanorods. Mater. Res. Bull. 2013, 48, 3383– 3388,  DOI: 10.1016/j.materresbull.2013.05.016
      15
      Synthesis, characterization and formation mechanism of metastable phase VO2(A) nanorods
      Cheng, X. H.; Xu, H. F.; Wang, Z. Z.; Zhu, K. R.; Li, G.; Jin, Shaowei
      Materials Research Bulletin (2013), 48 (9), 3383-3388CODEN: MRBUAC; ISSN:0025-5408. (Elsevier Ltd.)
      Pure phase VO2(A) nanorods were synthesized via the redn. of V2O5 by oxalic acid during the hydrothermal treatment. Two sets of samples were prepd. by varying both system temp. and reaction time under a filling ratio of 0.40 for observing the formation and evolution of VO2(A) nanorods. Structures were characterized by X-ray diffraction, scanning and transmission electron microscopies, resp. It was found that VO2(B) was firstly formed and then transformed into VO2(A) as the increasing system temp. or extending reaction time. An assembling and following crystal adjustment was proposed for explanation the formation process of VO2(A) from VO2(B). For VO2(A) nanorods, the phase transition temp. of 169.7°C was higher than that of the VO2(A) bulk, it might be ascribed to the lower crystallinity or nonstoichiometry in VO2(A) nanorods. VO2 nanostructures with controllable phases and properties should find their promising applications in a single VO2 nanodevice.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXovVCms7c%253D&md5=a5f9bc3aa90d57928080e541829afa04
    16. 16
      Zhang, L.; Xia, F.; Song, Z.; Webster, N. A. S.; Luo, H.; Gao, Y. Synthesis and formation mechanism of VO2(A) nanoplates with intrinsic peroxidase-like activity. RSC Adv. 2015, 5, 61371– 61379,  DOI: 10.1039/c5ra11014a
      16
      Synthesis and formation mechanism of VO2(A) nanoplates with intrinsic peroxidase-like activity
      Zhang, Liangmiao; Xia, Fang; Song, Zhengdong; Webster, Nathan A. S.; Luo, Hongjie; Gao, Yanfeng
      RSC Advances (2015), 5 (75), 61371-61379CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Monocryst. VO2(A) nanoplates were synthesized via a 1-pot hydrothermal process. In situ powder x-ray diffraction was used to monitor the hydrothermal synthesis and VO2(A) nucleates and grows directly from soln. after the complete hydrolysis of a 2.0M VO(acac)2 precursor soln., rather than involving a previously reported intermediate phase VO2(B). A hydrating-exfoliating-splitting mechanism was established to explain the formation of the nanoplate architecture. The synthesized VO2(A) nanoplates showed outstanding peroxidase-like activity and hence are a promising candidate for artificial peroxidase.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtFChtLrL&md5=f3ad20d4327c286dc3fbafce611c073a
    17. 17
      Zhang, S.; Shang, B.; Yang, J.; Yan, W.; Wei, S.; Xie, Y. From VO2(B) to VO2(A) nanobelts: first hydrothermal transformation, spectroscopic study and first principles calculation. Phys. Chem. Chem. Phys. 2011, 13, 15873– 15881,  DOI: 10.1039/c1cp20838a
      17
      From VO2 (B) to VO2 (A) nanobelts: first hydrothermal transformation, spectroscopic study and first principles calculation
      Zhang, Shudong; Shang, Bo; Yang, Jinlong; Yan, Wensheng; Wei, Shiqiang; Xie, Yi
      Physical Chemistry Chemical Physics (2011), 13 (35), 15873-15881CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      The phase transition process from VO2 (B) to VO2 (A) was first obsd. through a mild hydrothermal approach, using hybrid d. functional theory (DFT) calcns. and crystallog. VO2 topol. anal. All theor. analyses reveal that VO2 (A) is a thermodynamically stable phase and has a lower formation energy compared with the metastable VO2 (B). For the first time, X-ray absorption spectroscopy (XAS) of the V L-edge and O K-edge was performed on different VO2 phases, and the differences in the electronic structure of the two polymorphic forms provide further exptl. evidence of the more stable VO2 (A). Consequently, transformation from VO2 (B) to VO2 (A) is much easier to be realized from a dynamical point of view. Notably, the transformation of VO2 (B) into VO2 (A) show the sequence VO2 (B)-high-temp. VO2 (AH) phase-low-temp. VO2 (A) phase, which was achieved by hydrothermal treatment, resp. Also, an alternative synthesis route was proposed based on the above hydrothermal transformation, and VO2 (A) was successfully prepd. via the simple one-step hydrothermal method by hydrolysis of VO(acac)2 (acac = acetylacetonate). Therefore, VO2 nanostructures with controlled phase compns. can be obtained in high yields. Through elucidating the structural evolution in the crystallog. shear mechanism, we can easily guide the design of other metal oxide nanostructures with controllable phases.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGqu7bN&md5=39cdf6a5903c9c1ccf91631e97f28cb5
    18. 18
      Zhang, S.; Li, Y.; Wu, C.; Zheng, F.; Xie, Y. Novel Flowerlike Metastable Vanadium Dioxide (B) Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries. J. Phys. Chem. C 2009, 113, 15058– 15067,  DOI: 10.1021/jp903312h
      18
      Novel Flowerlike Metastable Vanadium Dioxide (B) Micronanostructures: Facile Synthesis and Application in Aqueous Lithium Ion Batteries
      Zhang, Shudong; Li, Yingmei; Wu, Changzheng; Zheng, Fei; Xie, Yi
      Journal of Physical Chemistry C (2009), 113 (33), 15058-15067CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Novel flowerlike VO2(B) micro-nanostructures assembled by single-cryst. nanosheets were synthesized via a hydrothermal route using polymer polyvinyl pyrrolidone (PVP, K30) as capping reagent. Detailed proofs indicated that the process of crystal growth was dominated by a nucleation and growth, self-assembly, and then Ostwald ripening growth mechanism. The flowerlike micro-nanostructured VO2(B) was applied as the active material in aq. Li-ion batteries which showed improved electrochem. properties with the 1st discharge capacity reaching 74.9 mA-h/g, a good value for aq. Li ion battery systems in light of previous reports (usually <65 mA-h/g). Corresponding VO2(B) nanostructures with better crystallinity were obtained by calcining the precursor of flowerlike VO2(B) structures. The post-treated flowerlike VO2(B) electrode shows better electrochem. properties with the 1st discharge capacity reaching 81.3 mA-h/g, which is higher than that of the flowerlike VO2(B) sample before annealing. The electrochem. intercalation and deintercalation properties of VO2(B) nanobelts and carambola-like VO2(B) structures with Li+ were also studied. The unique flowerlike structure plays a role in the morphol. requirement to serve as transport paths for Li ions in aq. Li ion batteries. The morphol. and crystallinity of the synthesized products had an influence on the electrochem. intercalation and deintercalation properties with Li ions.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXovFKlt74%253D&md5=853e81161aac174de5b76d5e68fc5045
    19. 19
      Walton, R. I. Subcritical solvothermal synthesis of condensed inorganic materials. Chem. Soc. Rev. 2002, 31, 230– 238,  DOI: 10.1039/b105762f
      19
      Subcritical solvothermal synthesis of condensed inorganic materials
      Walton, Richard I.
      Chemical Society Reviews (2002), 31 (4), 230-238CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. The solvothermal method has recently been extended from zeolite synthesis to the formation of condensed inorg. solids, which find uses in diverse areas due to properties such as ionic-cond., solid-state magnetism, giant magnetoresistance, low thermal expansion and ferroelectricity. This offers specific advantages over the traditional ceramic synthetic routes to inorg. solids and these are highlighted with examples from the recent literature, and the efforts focussed on detg. the formation mechanism of solids from the heterogeneous mixts. used in solvothermal procedures are discussed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XkvVCmt7o%253D&md5=ac8805ccaff49f722b4c472ee85726da
    20. 20
      Yu, W.; Li, S.; Huang, C. Phase evolution and crystal growth of VO2 nanostructures under hydrothermal reactions. RSC Adv. 2016, 6, 7113– 7120,  DOI: 10.1039/c5ra23898f
      20
      Phase evolution and crystal growth of VO2 nanostructures under hydrothermal reactions
      Yu, Weilai; Li, Shuai; Huang, Chi
      RSC Advances (2016), 6 (9), 7113-7120CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      The phase evolution and crystal growth of VO2 nanostructures against reaction time in a high-pressure V2O5-oxalic acid hydrothermal system were systematically investigated. It was found that the rather thin VO2 (B) nanobelts were first obtained, then stacked to form large belt-like structures and subsequently phase transformed into VO2 (A), based on an oriented attachment-recrystn. mechanism. The large VO2 (A) belt-like structures could further assemble into novel "snowflake" VO2 (M) microcrystals with even bigger sizes and nearly well-defined six-fold symmetry. Due to the Ostwald ripening effect regarding crystal size discrepancy, the VO2 (M) phase could further grow at the cost of the gradual dissoln. of VO2 (A) and full elimination of VO2 (B). The phase evolution from VO2 (B) first to VO2 (A) and then to VO2 (M), is actually a step-by-step thermodynamically downhill process, owing to the gradual relaxation of structural tension within the VO2 crystal lattice. Thus, our investigation, for the first time, demonstrated the feasibility of the well-known Ostwald's step rules towards the phase evolution process of VO2 and could provide unprecedented new insight to promote understanding of the synthesis and properties of vanadium oxide compds.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlvV2lsQ%253D%253D&md5=38c86bd180df72c567bacbc3a3b8057d
    21. 21
      Beidelman, B. A.; Zhang, X.; Sanchez-Lievanos, K. R.; Selino, A. V.; Matson, E. M.; Knowles, K. E. Influence of water concentration on the solvothermal synthesis of VO2(B) nanocrystals. CrystEngComm 2022, 24, 6009– 6017,  DOI: 10.1039/d2ce00813k
      21
      Influence of water concentration on the solvothermal synthesis of VO2(B) nanocrystals
      Beidelman, Brittney A.; Zhang, Xiaotian; Sanchez-Lievanos, Karla R.; Selino, Annabel V.; Matson, Ellen M.; Knowles, Kathryn E.
      CrystEngComm (2022), 24 (34), 6009-6017CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      Nanocrystals of VO2(B) have attracted significant attention for their promising performance in electrochem. energy storage applications. Phase-purity and nanocrystal morphol. are both crucial factors for the performance of these materials, but given the large no. of crystal polymorphs available to VO2, achieving simultaneous control over crystal phase and nanocrystal size is a significant synthetic challenge. This paper describes the impact of water concn. on the synthesis of VO2(B) nanocrystals via solvothermal reaction of a mol. V(IV) precursor in toluene. Using controlled, stoichiometric amts. of water (20 equiv per vanadium center) enables access to short nanorods of VO2(B) whose lengths follow a Gaussian distribution with an av. and std. deviation of 110 ± 30 nm. Decreasing the amt. of water present to two or four equiv. results in formation of VO2(A) nanocrystals and eliminating it entirely results in no reaction. Increasing the amt. of water to more than 20 equiv increases the av. length of the VO2(B) nanorods and causes the distribution in rod lengths to evolve from Gaussian to lognormal. This evolution in the size distribution is consistent with changes in a model Gaussian distribution obsd. upon simulated end-to-end oriented attachment events. These results demonstrate that control over the concn. of water is a useful strategy for tuning the morphol. and crystal phase of VO2 nanocrystals.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitV2ks73O&md5=9d7d4808dd7ab07a57b23fb3525febaa
    22. 22
      Serjeant, E. P.; Dempsey, B. Ionisation Constants of Organic Acids in Aqueous Solution; Pergamon Press: New York, New York, 1979; Vol. 23.
      There is no corresponding record for this reference.
    23. 23
      Haynes, W. H. CRC Handbook of Chemistry and Physics, 91st ed.; CRC Press Inc.: Boca Raton, FL, 2010–2011.
      There is no corresponding record for this reference.
    24. 24
      Dean, J. A. Lange’s Handbook of Chemistry, 13th ed.; McGraw-Hill Book Co: New York, NY, 1985.
      There is no corresponding record for this reference.
    25. 25
      Muckerman, J. T.; Skone, J. H.; Ning, M.; Wasada-Tsutsui, Y. Toward the accurate calculation of pKa values in water and acetonitrile. Biochim. Biophys. Acta, Bioenerg. 2013, 1827, 882– 891,  DOI: 10.1016/j.bbabio.2013.03.011
      25
      Toward the accurate calculation of pKa values in water and acetonitrile
      Muckerman, James T.; Skone, Jonathan H.; Ning, Ming; Wasada-Tsutsui, Yuko
      Biochimica et Biophysica Acta, Bioenergetics (2013), 1827 (8-9), 882-891CODEN: BBBEB4; ISSN:0005-2728. (Elsevier B. V.)
      We present a simple approach for the calcn. of accurate pKa values in water and acetonitrile based on the straightforward calcn. of the gas-phase abs. free energies of the acid and conjugate base with use of only a continuum solvation model to obtain the corresponding soln.-phase free energies. Most of the error in such an approach arises from inaccurate differential solvation free energies of the acid and conjugate base which is removed in our approach using a correction based on the realization that the gas-phase acidities have only a small systematic error relative to the dominant systematic error in the differential solvation. The methodol. is outlined in the context of the calcn. of a set of neutral acids with water as the solvent for a reasonably accurate electronic structure level of theory (DFT), basis set, and implicit solvation model. It is then applied to the comparison of results for three different hybrid d. functionals to illustrate the insensitivity to the functional. Finally, the approach is applied to the comparison of results for sets of neutral acids and protonated amine cationic acids in both aq. (water) and nonaq. (acetonitrile) solvents. The methodol. is shown to generally predict the pKa values for all the cases investigated to within 1 pH unit so long as the differential solvation error is larger than the systematic error in the gas-phase acidity calcns. Such an approach is rather general and does not have addnl. complications that would arise in a cluster-continuum method, thus giving it strength as a simple high-throughput means to calc. abs. pKa values. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXmsFCjtbk%253D&md5=c6e56760baf2f86e8940fcd72bb08af1
    26. 26
      Weeks, C.; Song, Y.; Suzuki, M.; Chernova, N. A.; Zavalij, P. Y.; Whittingham, M. S. The one dimensional chain structures of vanadyl glycolate and vanadyl acetate. J. Mater. Chem. 2003, 13, 1420– 1423,  DOI: 10.1039/b208100h
      26
      The one dimensional chain structures of vanadyl glycolate and vanadyl acetate
      Weeks, Curtis; Song, Yanning; Suzuki, Masatsugu; Chernova, Natasha A.; Zavalij, Peter Y.; Whittingham, M. Stanley
      Journal of Materials Chemistry (2003), 13 (6), 1420-1423CODEN: JMACEP; ISSN:0959-9428. (Royal Society of Chemistry)
      The solvothermal reaction, at 200°, of vanadium pentoxide and lithium hydroxide in acetic acid or ethylene glycol gives vanadyl acetate and vanadyl glycolate resp. The structure of the acetate contains vanadium in octahedral coordination whereas the glycolate contains VO5 square pyramids. The VO6 octahedra in the acetate, VO(CH3COO)2, are joined through the vanadyl groups, giving a rather long V:O bond of 1.684(7) Å and a short trans V-O bond of 2.131(7) Å, and by bridging acetate groups. The vanadium atoms interact along the ···V:O···V:O··· chain giving 1-dimensional antiferromagnetic behavior. In contrast in the glycolate, the apical V:O bond is shorter, 1.58(1) Å, and the square pyramids share edges in a two up-two down fashion to give chains VO(OCH2CH2O). Magnetic susceptibility of vanadyl glycolate is consistent with an isolated spin dimers model.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXjvVCgsLc%253D&md5=b570fd9cea9efed13b78c01cc79cd069
    27. 27
      Casey, A. T.; Thackeray, J. R. The preparation and magnetic properties of oxovanadium(IV) acetate. Aust. J. Chem. 1969, 22, 2549– 2553,  DOI: 10.1071/ch9692549
      27
      Preparation and magnetic properties of oxovandium(IV) acetate
      Casey, Allan T.; Thackery, J. R.
      Australian Journal of Chemistry (1969), 22 (12), 2549-53CODEN: AJCHAS; ISSN:0004-9425.
      The variation of the magnetic susceptibility of oxovanadium(IV) acetate with temp. may be fitted to the Ising model of an infinite linear antifer romagnetic chain with exchange energy of -166 cm-1. On the basis of this and ir evidence, a structure for the compd. is proposed.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3cXjslWmsg%253D%253D&md5=6c034e42b8006146026c3a6ed3ef4aa6
    28. 28
      Dakternieks, D. R.; Harris, C. M.; Milham, P. J.; Morris, B. S.; Sinn, E. Magnetism and structure of polymeric oxovanadium(IV) acetate and other polymeric oxovanadium(IV) complexes. Inorg. Nucl. Chem. Lett. 1969, 5, 97– 100,  DOI: 10.1016/0020-1650(69)80177-7
      28
      Magnetism and structure of polymeric oxovanadium(IV) acetate and other polymeric oxovanadium(VI) complexes
      Dakternieks, D. R.; Harris, Clive Melville; Milham, P. J.; Morris, Benjamin S.; Sinn, Ekkehard
      Inorganic and Nuclear Chemistry Letters (1969), 5 (2), 97-100CODEN: INUCAF; ISSN:0020-1650.
      From magnetic and other evidence, it is concluded that oxovanadium(IV) acetate and other carboxylate complexes consist of polymeric structures. The V:O stretching absorption at 895 cm.-1 gives a force const. k of 5.8 millidynes/A.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF1MXhtF2mt7s%253D&md5=a63282881ea3c3e5c17a11c0144f2955
    29. 29
      Ikekwere, P. O.; Adeniyi, A. A. Oxovanadium(IV) Complexes of Some Aromatic Carboxylic Acids. Synth. React. Inorg. Met.-Org. Chem. 1989, 19, 87– 100,  DOI: 10.1080/00945718908048053
      29
      Oxovanadium(IV) complexes of some aromatic carboxylic acids
      Ikekwere, P. O.; Adeniyi, A. A.
      Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1989), 19 (1), 87-100CODEN: SRIMCN; ISSN:0094-5714.
      VOL2.nH2O (L = BzOH and its 2-, 3- and 4-cyano-, 3-cyano-4-methyl-, 2-, 3- and 4-methyl-, 2,5- and 3,5-dimethyl-, 2,4,6-trimethyl-, 2-, 3- and 4-nitro derivs.) were prepd. and characterized by their magnetic and spectral properties. The complexes had magnetic moments much lower than the spin-only value of 1.73 μB at room temp. indicating strong magnetic interactions. Their Nujol mull spectra showed 3 main electronic absorption bands typical of tetragonally distorted octahedral oxovanadium(IV) compds. The IR vibrational spectra indicate that the carboxylate groups are bridging. The complexes are carboxylate-bridged polymers with V:O...V:O interaction.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXktFKltbs%253D&md5=ab83fb438d173fba7cf52badac767214
    30. 30
      Puri, M.; Sharma, R. D.; Verma, R. D. Trifluoroacetates of Vanadium(III) and Oxovanadium(IV) and (V) Preparation and Characterization. Synth. React. Inorg. Met.-Org. Chem. 1981, 11, 539– 546,  DOI: 10.1080/00945718108055998
      30
      Trifluoroacetates of vanadium(III) and oxovanadium(IV) and (V). Preparation and characterization
      Puri, Madhu; Sharma, R. D.; Verma, Rajendar D.
      Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry (1981), 11 (6), 539-46CODEN: SRIMCN; ISSN:0094-5714.
      V(O2CCF3)3 (I), VO(O2CCF3)2 (II), and VO2(O2CCF3) were prepd. by treating VCl3, VOCl2, and VOCl3, resp., with CF3CO2H. I and II were also prepd. by heating V(OAc)3 and VO(OAc)2 with CF3CO2H. The IR spectra, thermal degrdn., magnetic susceptibilities, and reflectance spectra of the compds. were detd.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL38Xht1aitLs%253D&md5=dfdabce00d2634d5c7519bd8d3f3a35d
    31. 31
      Lorenzotti, A.; Leonesi, D.; Cingolani, A.; Di Bernardo, P. Vanadyl(IV)─Acetate complexes in aqueous solution. J. Inorg. Nucl. Chem. 1981, 43, 737– 738,  DOI: 10.1016/0022-1902(81)80213-8
      31
      Vanadyl(IV)-acetate complexes in aqueous solution
      Lorenzotti, Adriana; Leonesi, Dante; Cingolani, Augusto; Di Bernardo, Plinio
      Journal of Inorganic and Nuclear Chemistry (1981), 43 (4), 737-8CODEN: JINCAO; ISSN:0022-1902.
      The formation of vanadyl(IV) complexes with acetates were studied by potentiometric titrn. methods; the stability consts. of mononuclear complexes, [VO(CH3COO)]+ and [VO(CH3COO)2], were calcd. to be 72.2 and 12.6 M-1, resp., in 1M aq. perchlorate at 25°. A comparison was made with the literature values for the corresponding neptunyl(IV) complexes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXktlWht78%253D&md5=d53355c3f23bd1243e57ac91ab797f5b
    32. 32
      Di Bernardo, P.; Tomat, G.; Zanonato, P.; Portanova, R.; Tolazzi, M. Thermodynamics of vanadyl(IV)─carboxylate complex formation in aqueous solution. Inorg. Chim. Acta 1988, 145, 285– 288,  DOI: 10.1016/s0020-1693(00)83971-7
      32
      Thermodynamics of vanadyl(IV)-carboxylate complex formation in aqueous solution
      Di Bernardo, Plinio; Tomat, Giuliana; Zanonato, Pierluigi; Portanova, Roberto; Tolazzi, Marilena
      Inorganica Chimica Acta (1988), 145 (2), 285-8CODEN: ICHAA3; ISSN:0020-1693.
      The stability consts. and the heats of formation of vanadyl(IV)-acetate, -glycolate, and -glycine complexes were detd. in aq. soln. by potentiometric and calorimetric measurements. In the pH range where the protolytic equil. of VO2+ is negligible, acetate forms 2 mononuclear complexes, glycolate 3, while glycine reacts in its zwitterionic form. The stabilities of the glycolate complexes are considerably higher than the acetate complexes, in spite of its lower basicity, indicating that complex formation involves the coordination of the OH group. The enthalpy changes are pos. except for glycolate where a small neg. value is found. For all systems, the entropy changes are pos. and therefore favorable to the complex formation.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1cXltFOjur8%253D&md5=f08fc3a701e03e24092175d6e4861700
    33. 33
      Mehio, N.; Ivanov, A. S.; Ladshaw, A. P.; Dai, S.; Bryantsev, V. S. Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents. Ind. Eng. Chem. Res. 2016, 55, 4231– 4240,  DOI: 10.1021/acs.iecr.5b03398
      33
      Theoretical Study of Oxovanadium(IV) Complexation with Formamidoximate: Implications for the Design of Uranyl-Selective Adsorbents
      Mehio, Nada; Ivanov, Alexander S.; Ladshaw, Austin P.; Dai, Sheng; Bryantsev, Vyacheslav S.
      Industrial & Engineering Chemistry Research (2016), 55 (15), 4231-4240CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)
      Poly(acrylamidoxime) fibers are the current state-of-the-art adsorbent for mining uranium from seawater. However, the competition between uranyl (UO22+) and vanadium ions poses a challenge to mining on the industrial scale. In this work, we employ d. functional theory and coupled-cluster methods in the restricted formalism to investigate potential binding motifs of the oxovanadium(IV) ion (VO2+) with the formamidoximate ligand. Consistent with exptl. extended X-ray absorption fine structure data, the hydrated six-coordinate complex is predicted to be preferred over the hydrated five-coordinate complex. Our investigation of formamidoximate-VO2+ complexes universally identified the most stable binding motif formed by chelating a tautomerically rearranged imino hydroxylamine via the imino nitrogen and hydroxylamine oxygen. The alternative binding motifs for amidoxime chelation via a nonrearranged tautomer and η2 coordination are found to be ∼11 kcal/mol less stable. Natural bond orbital anal. was performed to understand the nature of the interactions in the VO2+ complexes. The difference in the most stable VO2+ and UO22+ binding conformation has important implications for the design of more selective UO22+ ligands.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVyit7jL&md5=ffaf2049955182832f1549baa63c4f99
    34. 34
      Winkler, J. R.; Gray, H. B. Electronic Structures of Oxo-Metal Ions. In Molecular Electronic Structures of Transition Metal Complexes I. Structure and Bonding; Mingos, D. M. P., Day, P., Dahl, J. P., Eds.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2012; vol. 142, pp 17– 28.
      There is no corresponding record for this reference.
    35. 35
      Krakowiak, J.; Lundberg, D.; Persson, I. A Coordination Chemistry Study of Hydrated and Solvated Cationic Vanadium Ions in Oxidation States +III, +IV, and +V in Solution and Solid State. Inorg. Chem. 2012, 51, 9598– 9609,  DOI: 10.1021/ic300202f
      35
      A Coordination Chemistry Study of Hydrated and Solvated Cationic Vanadium Ions in Oxidation States +III, +IV, and +V in Solution and Solid State
      Krakowiak, Joanna; Lundberg, Daniel; Persson, Ingmar
      Inorganic Chemistry (2012), 51 (18), 9598-9609CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)
      The coordination chem. of hydrated and solvated vanadium(III), oxovanadium(IV), and dioxovanadium(V) ions in the oxygen-donor solvents water, DMSO , and N,N'-dimethylpropyleneurea (DMPU) was studied in soln. by extended x-ray absorption fine structure (EXAFS) and large-angle X-ray scattering (LAXS) and in the solid state by single-crystal X-ray diffraction and EXAFS. The hydrated vanadium(III) ion has a regular octahedral configuration with a mean V-O bond distance of 1.99 Å. In the hydrated and DMSO-solvated oxovanadium(IV) ions, vanadium binds strongly to an oxo group at ∼1.6 Å. The solvent mol. trans to the oxo group is very weakly bound, at ∼2.2 Å, while the remaining four solvent mols., with a mean V-O bond distance of 2.0 Å, form a plane slightly below the vanadium atom; the mean O=V-Operp bond angle is ∼98°. In the DMPU-solvated oxovanadium(IV) ion, the space-demanding properties of the DMPU mol. leave no solvent mol. in the trans position to the oxo group, which reduces the coordination no. to 5. The O=V-O bond angle is consequently much larger, 107°, and the mean V=O and V-O bond distances decrease to 1.58 and 1.97 Å, resp. The hydrated and DMSO-solvated dioxovanadium(V) ions display a very distorted octahedral configuration with the oxo groups in the cis position with a mean V=O bond distance of 1.6 Å and a O=V=O bond angle of ∼105°. The solvent mols. trans to the oxo groups are weakly bound, at ∼2.2 Å, while the remaining two have bond distances of 2.02 Å. The exptl. studies of the coordination chem. of hydrated and solvated vanadium(III,IV,V) ions are complemented by summarizing previously reported crystal structures to yield a comprehensive description of the coordination chem. of vanadium with oxygen-donor ligands.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlSks7nL&md5=e69f2a1d2daac25be6f4a51cedebef0b
    36. 36
      Rumble, J. R. CRC Handbook of Chemistry and Physics, Internet Edition 2018, 99th ed.; CRC Press/Taylor & Francis: Boca Raton, FL, 2018.
      There is no corresponding record for this reference.
    37. 37
      Guo, Y.; Surblys, D.; Matsubara, H.; Kawagoe, Y.; Ohara, T. Molecular Dynamics Study on the Effect of Long-Chain Surfactant Adsorption on Interfacial Heat Transfer between a Polymer Liquid and Silica Surface. J. Phys. Chem. C 2020, 124, 27558– 27570,  DOI: 10.1021/acs.jpcc.0c08940
      37
      Molecular dynamics study on effect of long-chain surfactant adsorption on interfacial heat transfer between polymer liquid and silica surface
      Guo, Yuting; Surblys, Donatas; Matsubara, Hiroki; Kawagoe, Yoshiaki; Ohara, Taku
      Journal of Physical Chemistry C (2020), 124 (50), 27558-27570CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      The addn. of surfactants to polymer-based thermal interface materials applied to improve the heat dissipation efficiency of chip surfaces in contact has attracted attention for the microelectronic processing technol. In the present study, the mechanism by which a long-chain surfactant affects heat transfer across the interface between solid surface and polymer liq. was investigated by non-equil. mol. dynamics simulation. We constructed a system where tetracosane was used as a solvent and contained alc. mols. as a surfactant, and they were placed between two flat silica surfaces under a thermal gradient. The effect of the hydrophilicity of silica surface, the concn. of the surfactant, and chain length of the surfactant on silica-liq. interfacial thermal resistance Rb were examd. Alc. surfactant mols. preferred to adsorb onto the hydrophilic silica (Si-OH) surface due to hydrogen bonding between alc. and silanol hydroxyl groups. It was found that Rb reduced not only with the adsorption amt. of alc. mols. but also with the chain length of alc. The van der Waals interaction contribution was dominant for solid-liq. and liq.-liq. heat conduction near the interface. The hydroxyl terminals of alc. mols. were vertically adsorbed onto the Si-OH surface due to hydrogen bonds, which produced a heat path from silanols to the hydroxyl groups of alc. Furthermore, heat was also exchanged between alc. hydroxyl and alkyl groups via intramol. interaction and between the alc. alkyl groups and nearby solvent mols. via van der Waals (vdW) intermol. interaction. This resulted in an efficient heat path from solid surface silanols to liq. bulk. As the alc. chain length increased without changing the no. of adsorbed alc. mols., the heat transfer through this heat path increased, which led to a decrease in Rb. These results provided insight toward the guiding principle for the mol. design of complex surfactants to enhance the interfacial heat transfer.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXisV2hu73K&md5=b84d8894327b9cc141f818c12772aef2
    38. 38
      Uchaker, E.; Gu, M.; Zhou, N.; Li, Y.; Wang, C.; Cao, G. Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano-Structured Electrode Materials: Vanadium Oxide Mesocrystals. Small 2013, 9, 3880– 3886,  DOI: 10.1002/smll.201203187
      38
      Enhanced Intercalation Dynamics and Stability of Engineered Micro/Nano-Structured Electrode Materials: Vanadium Oxide Mesocrystals
      Uchaker, Evan; Gu, Meng; Zhou, Nan; Li, Yanwei; Wang, Chongmin; Cao, Guozhong
      Small (2013), 9 (22), 3880-3886CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
      An additive and template free process is developed for the facile synthesis of VO2(B) mesocrystals via the solvothermal reaction of oxalic acid and vanadium pentoxide. The six-armed star architectures are composed of stacked nanosheets homoepitaxially oriented along the [100] crystallog. register with respect to one another, as confirmed by means of selected area electron diffraction and electron microscopy. It is proposed that the mesocrystal formation mechanism proceeds through classical as well as non-classical crystn. processes, and is possibly facilitated or promoted by the presence of a reducing/chelating agent. The synthesized VO2(B) mesocrystals are tested as a cathodic electrode material for lithium-ion batteries, and show good capacity at discharge rates ranging from 150-1500 mA g-1 and a cyclic stability of 195 mA h g-1 over fifty cycles. The superb electrochem. performance of the VO2(B) mesocrystals is attributed to the porous and oriented superstructure that ensures large surface area for redox reaction and short diffusion distances. The mesocryst. structure ensures that all the surfaces are in intimate contact with the electrolyte, and that lithium-ion intercalation occurs uniformly throughout the entire electrode. The exposed (100) facets also lead to fast lithium intercalation, and the homoepitaxial stacking of nanosheets offers a strong inner-sheet binding force that leads to better accommodation of the strain induced during cycling, thus circumventing the capacity fading issues typically assocd. with VO2(B) electrodes.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXntF2ksLk%253D&md5=6c44f9f3abed96d1ede41c768401b5a9
    39. 39
      Zeininger, L.; Portilla, L.; Halik, M.; Hirsch, A. Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles. Chem.─Eur. J. 2016, 22, 13506– 13512,  DOI: 10.1002/chem.201601920
      39
      Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles
      Zeininger, Lukas; Portilla, Luis; Halik, Marcus; Hirsch, Andreas
      Chemistry - A European Journal (2016), 22 (38), 13506-13512CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The adsorption, desorption, co-adsorption, and exchange of phosphonic acid, carboxylic acid, and catechol derivs. on the surface of titanium oxide (anatase) nanoparticles are investigated. Thermogravimetric anal. provides a facile and fast-track quant. detn. of the wet-chem. monolayer adsorption consts. and grafting densities of ten adsorbates, all under neutral pH conditions. This characterization protocol allows straightforward quantification of the relevant thermodn. data of ligand adsorption and a comparison of ligand adsorption strengths. The reported procedure is proposed as a universal tool and it should be applicable to many other colloidal metal oxide materials. Moreover, the detd. values for the adsorption consts. and the monolayer grafting densities provide a toolbox for the assessment of the adsorbates' behavior in desorption, exchange, and co-adsorption equil. This versatile evaluation procedure will help to identify optimal monolayer-surface combinations and to evaluate crit. parameters, such as monolayer robustness, ligand exchange rates, or targeted mixed assembly of functionalities.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xht1WmtLbL&md5=9c49d50096a1908a791fdd7cc4bf7991
    40. 40
      De Roo, J.; Justo, Y.; De Keukeleere, K.; Van den Broeck, F.; Martins, J. C.; Van Driessche, I.; Hens, Z. Carboxylic-Acid-Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif. Angew. Chem., Int. Ed. 2015, 54, 6488– 6491,  DOI: 10.1002/anie.201500965
      40
      Carboxylic-Acid-Passivated Metal Oxide Nanocrystals: Ligand Exchange Characteristics of a New Binding Motif
      De Roo, Jonathan; Justo, Yolanda; De Keukeleere, Katrien; Van den Broeck, Freya; Martins, Jose C.; Van Driessche, Isabel; Hens, Zeger
      Angewandte Chemie, International Edition (2015), 54 (22), 6488-6491CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Studying sterically stabilized HfO2 and ZrO2 NCs using 1H soln. NMR and IR spectroscopy as well as elemental anal., this paper demonstrates the reversible exchange of initial oleic acid ligands for octylamine and self-adsorption of oleic acid at NC surfaces. Both processes are incompatible with an X-type binding motif of carboxylic acids as reported for sulfide and selenide NCs. This behavior stems from the dissociative adsorption of carboxylic acids at the oxide surface. Both proton and carboxylate moieties must be regarded as X-type ligands yielding a combined X2 binding motif that allows for self-adsorption and exchange for L-type ligands.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmtlGqsr4%253D&md5=a55ec98a8761a97e2f1900720b8f7aa5
    41. 41
      Calatayud, D. G.; Rodríguez, M.; Jardiel, T. Controlling the morphology of TiO2 nanocrystals with different capping agents. Bol. Soc. Esp. Ceram. Vidrio 2015, 54, 159– 165,  DOI: 10.1016/j.bsecv.2015.07.001
      41
      Controlling the morphology of TiO2 nanocrystals with different capping agents
      Calatayud, David G.; Rodriguez, Monica; Jardiel, Teresa
      Boletin de la Sociedad Espanola de Ceramica y Vidrio (2015), 54 (4), 159-165CODEN: BSCVB9; ISSN:0366-3175. (Sociedad Espanola de Ceramica y Vidrio)
      This paper provides direct evidence to support the role of capping agents in controlling the evolution of TiO2 seeds into nanocrystals with a specific shape. Starting with Ti(OBut)4 and using oleid acid, oleylamine, dioleamide, 11-aminoundecanoic acid, arginine, trifluroacetic acid or HF as capping agents, mainly TiO2 truncated octahedrons enclosed by {1 0 1} and {0 0 1} facets were obtained. We could also selectively obtain square, rods and rounded rhombic-shaped nanoparticles by growing of {0 1 0} facets by adding oleic acid and oleylamine in ratio 6:4, resp., while all other parameters were kept the same. This research not only offers new insights into the role played by a capping agent in shape-controlled synthesis but also provides, a versatile approach to controlling the shape of metal oxide nanocrystals.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhs1Snu77O&md5=691f7e4efcd1878d15164aa9c21d983d

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsnanoscienceau.3c00014.

    • Tables reporting the amounts of all reagents used in each reaction reported here, powder X-ray diffraction spectra, TEM, and SEM images of nanocrystalline products, and details of the characterization of VO(benzoate)2 and VO(4-nitrobenzoate)2 by single-crystal electron diffraction (PDF)

    • Crystallographic data for VO(benozate)2 (CIF)

    • Crystallographic data for VO(4-nitrobenzoate)2 (CIF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.