State of the Art Progress in Copper Vanadate Materials for Solar Water Splitting.

The development of a single junction photoelectrode material having specific properties is essential and challenging for the efficient application in solar water splitting for oxygen production and a high value-added product, hydrogen. Moreover, the present material solutions based on binary metal oxides offer limited catalytic activity and hydrogen production efficiency. Therefore, it is paramount to develop and exploit a unique range of materials derived from ternary metal oxides with specifically engineered properties to advance in photoelectrochemical (PEC) water splitting. Among the ternary oxides, copper vanadates offer promising characteristics, such as a narrow bandgap and catalytic surface properties along with favorable band edges for facile oxygen evolution reaction (OER), which is considered the bottleneck step in performing overall water dissociation. Furthermore, the copper vanadates allow the tuning of the stoichiometry through which a wide range of polymorphs and materials could be obtained. This review provides a complete outlook on the range of copper vanadates and the established synthesis approach, morphology, crystal structure, band edge properties, and PEC characterizations. Mainly, the underlying charge dynamic properties, carrier path length, effect of doping, and influence of surface catalysts are discussed. The review concludes that the advancement toward obtaining low-bandgap materials is a main challenge to overcome the limitations for efficient water dissociation to OER and copper vanadates, which offer a promising solution with their unique properties and advantages. Importantly, intense and strategically focused research is vital to overcome the scientific challenges involved in copper vanadates and to explore and exploit new polymorphs to set new efficiency benchmarks and PEC water splitting solutions.

Enhanced photoactivity towards bismuth vanadate water splitting through tantalum doping: An experimental and density functional theory study.

The activation of hole trap states in bismuth vanadate (BiVO4) is considered an effective strategy to enhance the photoelectrochemical (PEC) water-splitting activity. Herein, we propose a theoretical and experimental study of tantalum (Ta) doping to BiVO4 leading to the introduction of hole trap states for the enhanced PEC activity. The doping of Ta is found to alter the structural and chemical surroundings via displacement of vanadium (V) atoms that cause distortions in the lattice via the formation of hole trap states. A significant enhancement of photocurrent to ∼4.2 mA cm-2 was recorded attributing to the effective charge separation of efficiency of ∼96.7 %. Furthermore, the doping of Ta in the BiVO4 lattice offers improved charge transport in bulk and decreased charge transfer resistance at the electrolyte interface. The Ta-doped BiVO4 displays the effective production of hydrogen (H2) and oxygen (O2) under AM 1.5 G illumination with a faradaic efficiency of 90 %. Moreover, the density functional theory (DFT) study confirms the decrease in optical band gap and the activation of hole trap states below the conduction band (CB) with a contribution of Ta towards both valence and CB that increases the charge separation and majority charge carrier density, respectively. The findings of this work propose that the displacement of V sites with Ta atoms in BiVO4 photoanodes is an efficient approach for enhanced PEC activity.

WO3/rGO nanocomposite-based sensor for the detection and degradation of 4-Chlorophenol.

Chlorinated organic compounds are useful chemicals or intermediates that are used extensively in both industry and agriculture. The 4-chlorophenol (4CP) in low concentration poses a serious environmental problem and causes many health issues, including cancer and liver disease. In this work, we demonstrated the detection of 4CP at carbon paste electrodes modified using tungsten oxide (WO3) nanorods and reduced graphene oxide (rGO) nanoparticles. The significance of pH on the voltammetric response of 4CP was investigated, and it was discovered that an alkaline pH is an optimal condition for detecting substituted phenols. Moreover, parameters like heterogeneous rate constant, accumulation time, temperature effect, Gibb's free energy, scan rate, enthalpy, activation energy, and entropy were studied. The excellent catalytic and bulk properties of tungsten oxide nanostructures make it an effective modifier in electrochemical sensors. The employment of nanostructured WO3 for the assay of 4CP offers excellent sensitivity, selectivity, and applicability. The WO3 nanostructures are obtained hydrothermally and characterized in detail to understand the crystalline, quantitative and chemical properties. The electrochemical behavior of 4CP was studied utilizing voltammetry techniques. The CV technique was used to optimize and affect many factors in the electrochemical behavior of 4CP. The scan rate investigation helps to examine the physicochemical characteristics of the electrode process, and the electrooxidation of 4CP included 2 electrons and 2 protons. With 4CP, the modified electrode displayed a broad range of linearity. The limit of detection was determined to be 0.102 nM, while the limit of quantification was 0.3433 nM. The concentration of 4CP ranged between 0.1 × 10-7 M and 3.5 × 10-7 M. The fabricated electrode was also used to detect 4CP in soil and water samples. Good recoveries were obtained from the soil and water samples. The proposed electrode was used for analytical applications, including 4CP detection with high selectivity, low detection limit, sensitivity, and rapid response.

Exploring the Synthesis, Band Edge Insights, and Photoelectrochemical Water Splitting Properties of Lead Vanadates.

Exploring the ideal and stable semiconductor material for the efficient photoelectrochemical (PEC) overall water splitting reaction has remained a major challenge. Herein, we develop a facile hydrothermal method for the fabrication of monoclinic Pb3[VO4]2 and orthorhombic PbV2O6 thin films for the efficient and stable PEC overall water splitting applications. Detailed characterization was performed to study the crystal structure and optical, electrical, and electrochemical properties. The band edge positions of Pb3[VO4]2 and PbV2O6 are determined using spectroscopic data, revealing the conduction band edge positioned near the water reduction potential [∼0 V vs reversible hydrogen electrode (RHE)] and the valence band edge positioned well above the water oxidation potential, indicating the possible utilization of photogenerated electrons and holes for efficient water reduction and oxidation, respectively. With the optimized PbV2O6 thin films, a maximum photocurrent of 0.35 mA cm-2 was obtained at 1.23 V versus RHE and the stable production of both O2 and H2 is observed with >90% Faradaic efficiency. Importantly, this work demonstrates the possibility of utilizing lead vanadate materials for PEC water splitting applications.

A novel sensor based on WO3·0.33H2O nanorods modified electrode for the detection and degradation of herbicide, carbendazim.

In the present-day scenario, it is necessary to establish more flexible, effective and selective analytical methods that are easy to operate and less expensive. Cyclic voltammetry (CV) can be a useful technique to assess minute quantity of pollutants and in this work, an effort has been made to detect the trace quantification from the environmental samples. Herein, electrochemical sensor was fabricated using tungsten oxide nanorod (WO3·0.33H2O) for sensitive detection of fungicide, carbendazim (CBZ). Under optimal conditions, while studying the effect of pH on peak current, the highest peak current was observed at pH 4.2. The degradation of CBZ followed the mixed diffusion-adsorption controlled and quasi-reversible processess at the WO3·0.33H2O/GC electrode surface. Using WO3·0.33H2O/GCE sensor in SWV provided the lowest limit of detection (LOD) and limit of quantification (LOQ) values of 2.21 × 10-8 M and 7.37 × 10-8 M, respectively over the concentration ranges of 1.0 × 10-7 M to 2.5 × 10-4 M. The proposed method demonstrates potential applicability of the fabricated sensor for soil and water samples analysis in the management of creating a benign environment.

Electrocatalytic detection of herbicide, amitrole at WO3·0.33H2O modified carbon paste electrode for environmental applications.

Environmental pollution by the heavy usage of pesticides has been a pandemic issue in view of the rising farming operations for increasing the crop yield to meet the requirements of food chain supply. Throughout the world, environmental pollution by the presence of pesticides, particularly the use of herbicides in large quantities to protect the crops, has posed many environmental issues. In this research, an electrochemical sensor based on tungsten oxide hydrates (WO3·0.33H2O) nanorod modified carbon paste electrode (CPE) was developed for the detection of herbicide, amitrole (AMT) by the cyclic voltammeter. Hydrothermally synthesized and characterized WO3·0.33H2O nanorod was found to be sensitive towards the detection of AMT due to its superior sensing property as the sensor showed enhanced current and catalytic property when used in phosphate buffer solution (PBS) of pH 5.0 by the cyclic voltammetric (CV) and square wave voltammetric (SWV) techniques. The influence of electro kinetic parameters viz., scan rate, pH, accumulation time and temperature with respect to AMT oxidation was studied using CV. The linearity range was in between 1.0 × 10-8 M and 24 × 10-5 M and limit of detection (LOD) and limit of quantification (LOQ) was calculated to be 2.33 nM and 7.8 nM respectively. The proposed simple method demonstrated the potential applicability to detect AMT from the soil and water samples.

Influence of molybdenum doping on the structural, optical and electronic properties of WO3 for improved solar water splitting.

Doping WO3 with foreign atoms is a very efficient strategy to modify the structural, optical and electronic properties which could influence its photoelectrochemical (PEC) water splitting activity. In this study, we report a simple and efficient single-step strategy for the fabrication of molybdenum (Mo)-doped WO3 thin films. The characterization results show that doping Mo into WO3 leads to a significant change in the morphology without changing its crystal structure. Elemental mapping and EDS analysis revealed that Mo was homogeneously doped into the crystal lattice of WO3 in the at.% range of 0-10.31. The incorporation of Mo into WO3 reduced the band-gap of WO3 and increased its light absorption ability. Notably, X-ray photoelectron spectroscopic valence band-edge analysis confirmed that substitution of Mo into WO3 led to a downward shift in the conduction band minimum without any significant change in the valence band maximum with respect to Fermi level. The fabricated Mo-doped WO3 electrodes exhibited a higher photocurrent compared to undoped WO3 samples under simulated 1.5AM sunlight without the addition of a water oxidation catalyst. The procedure proposed herein provides a simple and systematic approach for the fabrication of band-gap-tailored WO3 photoanodes by Mo doping for efficient PEC water splitting.

Monoclinic WO3 nanorods-rutile TiO2 nanoparticles core-shell interface for efficient DSSCs.

A core-shell photoanode, composed of a monoclinic WO3 nanorods core encapsulated with a rutile TiO2 nanoparticles shell, reveals ~246% enhancement in power conversion efficiency due to improved current density and open circuit voltage values and longer-lived charge carriers.

Interaction of triprolidine hydrochloride with serum albumins: thermodynamic and binding characteristics, and influence of site probes.

The interaction between triprolidine hydrochloride (TRP) to serum albumins viz. bovine serum albumin (BSA) and human serum albumin (HSA) has been studied by spectroscopic methods. The experimental results revealed the static quenching mechanism in the interaction of TRP with protein. The number of binding sites close to unity for both TRP-BSA and TRP-HSA indicated the presence of single class of binding site for the drug in protein. The binding constant values of TRP-BSA and TRP-HSA were observed to be 4.75 ± 0.018 × 10(3) and 2.42 ± 0.024 × 10(4)M(-1) at 294 K, respectively. Thermodynamic parameters indicated that the hydrogen bond and van der Waals forces played the major role in the binding of TRP to proteins. The distance of separation between the serum albumin and TRP was obtained from the Förster's theory of non-radioactive energy transfer. The metal ions viz., K(+), Ca(2+), Co(2+), Cu(2+), Ni(2+), Mn(2+) and Zn(2+) were found to influence the binding of the drug to protein. Displacement experiments indicated the binding of TRP to Sudlow's site I on both BSA and HSA. The CD, 3D fluorescence spectra and FT-IR spectral results revealed the changes in the secondary structure of protein upon interaction with TRP.

Interaction of an antidepressant buzepide methiodide with DNA immobilized on the glassy carbon electrode.

In the present study, a DNA-biosensor was prepared using immobilization technique to investigate the interaction between an antidepressant, buzepide methiodide (BZP) and calf thymus DNA. BZP showed a quasireversible peak in Britton-Robinson (BR) buffer of pH 5 at bare glassy carbon electrode (GCE). At DNA modified GCE, the peak potential of BZP was observed to be shifted towards positive potential revealing intercalative mode of binding. The binding constant and stoichiometry between DNA and BZP are calculated to be 1.908×10(5)M(-1) and 0.982, respectively. The spectroscopic techniques viz., spectrofluorescence and UV-vis absorption have also been employed to understand the interaction between BZP and DNA. The results serve as a reference for the interaction of BZP with DNA base pairs in the natural environment of living cells.

Characterization of interaction and the effect of carbamazepine on the structure of human serum albumin.

The binding of carbamazepine (CBZ) to human serum albumin (HSA) was investigated under simulative physiological conditions. In this study, intrinsic fluorescence of tryptophan-214 in HSA was monitored upon the addition of CBZ. Binding constant of CBZ-HSA was calculated by the remarkable static quenching effect of CBZ and found to be (2.081+/-0.023)x10(4)M(-1). The fluorimetric results revealed that the hydrophobic interaction was a predominant intermolecular force for stabilizing the complex, which is also in agreement with the results obtained from voltammetric approach. Three site probes, warfarin, ibuprofen and digitoxin, were employed in fluorescence displacement experiments to locate the exact binding site for CBZ in HSA. The alteration in secondary structure of protein in the presence of CBZ was confirmed by the evidences from circular dichroism and FT-IR spectroscopy. Further, the distance r between donor (Trp-214) and acceptor (CBZ) was obtained according to fluorescence resonance energy transfer (FRET).

Voltammetric sensor for buzepide methiodide determination based on TiO2 nanoparticle-modified carbon paste electrode.

In this work, we have prepared nano-material modified carbon paste electrode (CPE) for the sensing of an antidepressant, buzepide methiodide (BZP) by incorporating TiO2 nanoparticles in carbon paste matrix. Electrochemical studies indicated that the TiO2 nanoparticles efficiently increased the electron transfer kinetics between drug and the electrode. Compared with the nonmodified CPE, the TiO2-modified CPE greatly enhances the oxidation signal of BZP with negative shift in peak potential. Based on this, we have proposed a sensitive, rapid and convenient electrochemical method for the determination of BZP. Under the optimized conditions, the oxidation peak current of BZP is found to be proportional to its concentration in the range of 5 x 10(-8) to 5 x 10(-5)M with a detection limit of 8.2 x 10(-9)M. Finally, this sensing method was successfully applied for the determination of BZP in human blood serum and urine samples with good recoveries.

Voltammetric and spectroscopic investigations on the mechanism of interaction of buzepide methiodide with protein.

Adsorption or immobilization of proteins on solid surfaces promotes the biological responses to materials. Using immobilization technique, we have prepared human serum albumin (HSA) modified glassy carbon electrode (GCE) and employed it to probe the mode of interaction between antidepressant drug, buzepide methiodide (BZP) and HSA. At HSA modified GCE, the peak potential of BZP appeared at more positive potential compared to that at bare electrode thereby indicating the hydrophobic mode of interaction between BZP and HSA. Peak currents of BZP decreased upon the addition of HSA at bare GCE with positive shift in peak potential. Further, no new peaks were observed in presence of HSA. From electrochemical data, the binding constant and binding ratio between HSA and BZP were calculated to be 9.33 x 10(6)M(-1) and 1:2, respectively. FT-IR and circular dichroism (CD) studies revealed that the secondary structure of protein was perturbed upon interaction with BZP.

Probing the binding of fluoxetine hydrochloride to human serum albumin by multispectroscopic techniques.

The interaction between human serum albumin (HSA) and fluoxetine hydrochloride (FLX) have been studied by using different spectroscopic techniques viz., fluorescence, UV-vis absorption, circular dichroism and FTIR under simulated physiological conditions. Fluorescence results revealed the presence of static type of quenching mechanism in the binding of FLX to HSA. The values of binding constant, K of FLX-HSA were evaluated at 289, 300 and 310 K and were found to be 1.90x10(3), 1.68x10(3) and 1.45x10(3) M(-1), respectively. The number of binding sites, n was noticed to be almost equal to unity thereby indicating the presence of a single class of binding site for FLX on HSA. Based on the thermodynamic parameters, DeltaH(0) and DeltaS(0) nature of binding forces operating between HSA and FLX were proposed. Spectral results revealed the conformational changes in protein upon interaction. Displacement studies indicated the site I as the main binding site for FLX on HSA. The effect of common ions on the binding of FLX to HSA was also investigated.