BiVO4 As a Sustainable and Emerging Photocatalyst: Synthesis Methodologies, Engineering Properties, and Its Volatile Organic Compounds Degradation Efficiency.

Bismuth vanadate (BiVO4) is one of the best bismuth-based semiconducting materials because of its narrow band gap energy, good visible light absorption, unique physical and chemical characteristics, and non-toxic nature. In addition, BiVO4 with different morphologies has been synthesized and exhibited excellent visible light photocatalytic efficiency in the degradation of various organic pollutants, including volatile organic compounds (VOCs). Nevertheless, the commercial scale utilization of BiVO4 is significantly limited because of the poor separation (faster recombination rate) and transport ability of photogenerated electron-hole pairs. So, engineering/modifications of BiVO4 materials are performed to enhance their structural, electronic, and morphological properties. Thus, this review article aims to provide a critical overview of advanced oxidation processes (AOPs), various semiconducting nanomaterials, BiVO4 synthesis methodologies, engineering of BiVO4 properties through making binary and ternary nanocomposites, and coupling with metals/non-metals and metal nanoparticles and the development of Z-scheme type nanocomposites, etc., and their visible light photocatalytic efficiency in VOCs degradation. In addition, future challenges and the way forward for improving the commercial-scale application of BiVO4-based semiconducting nanomaterials are also discussed. Thus, we hope that this review is a valuable resource for designing BiVO4-based nanocomposites with superior visible-light-driven photocatalytic efficiency in VOCs degradation.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications.

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Polyaniline-wrapped MnMoO4 as an active catalyst for hydrogen production by electrochemical water splitting.

Developing efficient, low-cost, and environment-friendly electrocatalysts for hydrogen generation is critical for lowering energy usage in electrochemical water splitting. Moreover, for commercialization, fabricating cost-efficient, earth-abundant electrocatalysts with superior characteristics is of urgent need. Towards this endeavor, we report the synthesis of PANI-MnMoO4 nanocomposites using a hydrothermal approach and an in situ polymerization method with various concentrations of MnMoO4. The fabricated nanocomposite electrocatalyst exhibits bifunctional electrocatalytic activity towards the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) at a lower overpotential of 410 mV at 30 mA cm-2 and 155 mV at 10 mA cm-2, respectively in an alkaline electrolyte. Furthermore, while showing overall water splitting (OWS) performance, the optimized PM-10 (PANI-MnMoO4) electrode reveals the most outstanding OWS performance with a lower cell voltage of 1.65 V (vs. RHE) at a current density of 50 mA cm-2 with an excellent long-term cell resilience of 24 h.

Photoelectrochemical H2 evolution on WO3/BiVO4 enabled by single-crystalline TiO2 overlayer modulations.

Tungsten oxide/bismuth vanadate (WO3/BiVO4) has emerged as a promising photoanode material for photoelectrochemical (PEC) water splitting owing to its facilitated charge separation state differing significantly from single phase materials. Practical implementation of WO3/BiVO4 is often limited by poor stability arising from the leaching of V5+ from BiVO4 during PEC operations. Herein, we demonstrate that the synthesis of a tungsten oxide/bismuth vanadate/titanium oxide (WO3/BiVO4/TiO2) heterostructure onto a fluorine-doped tin oxide-coated glass substrate through a combined simple hydrothermal-spin coating strategy will advance PEC performance while slowing water oxidation kinetics and improving photostability. We show that surface postmodification with a nanometer-thick layer of (1 0 1) monofacet-selective single-crystalline TiO2 provides stable photocurrent density, up to 1.04 mA cm-2 at 1.23 V (compared to a reversible hydrogen electrode in 0.5 M Na2SO4), with excellent quantum efficiency (45% at 460 nm) and long-term photostability (24 h). Interestingly, crystalline TiO2 activation layers behave differently from previous TiO2 amorphous layers, blocking surface defects while improving corrosion resistance, photostability, and the electron transfer process. These results indicate a ≈2.5 times enhancement in photoelectrocatalytic activity related to referenced WO3/BiVO4 photoanodes, encouraging the use of single-crystalline TiO2 modulations to develop a range of materials for PEC/photocatalytic applications.

Microwave-Epoxide-Assisted Hydrothermal Synthesis of the CuO/ZnO Heterojunction: a Highly Versatile Route to Develop H2S Gas Sensors.

A robust synthesis approach to develop CuO/ZnO nanocomposites using microwave-epoxide-assisted hydrothermal synthesis and their proficiency toward H2S gas-sensing application are reported. The low-cost metal salts (Cu and Zn) as precursors in aqueous media and epoxide (propylene oxide) as a proton scavenger/gelation agent are used for the formation of mixed metal hydroxides. The obtained sol was treated using the microwave hydrothermal process to yield the high-surface area (34.71 m2/g) CuO/ZnO nanocomposite. The developed nanocomposites (1.25-10 mol % Cu doping) showcase hexagonal ZnO and monoclinic CuO structures, with an average crystallite size in the range of 18-29 nm wrt Cu doping in the ZnO matrix. The optimized nanocomposite (2.5 mol % Cu doping) showed a lowest crystallite size of 21.64 nm, which reduced further to 18.06 nm upon graphene oxide addition. Morphological analyses (scanning electron microscopy and transmission electron microscopy) exhibited rounded grains along with copious channels typical for sol-gel-based materials . Elemental mapping displayed the good dispersion of Cu in the ZnO matrix. When these materials are employed as a gas sensor, they demonstrated high sensitivity and selectivity toward H2S gas in comparison with the reducing gases and volatile organic compounds under investigation. The systematic doping of Cu in the ZnO matrix exhibited an improved response from 76.66 to 94.28%, with reduction in operating temperature from 300 to 250 °C. The 2.5 mol % doped Cu in ZnO was found to impart a response of 23 s for 25 ppm of H2S. Gas-sensing properties are described using an interplay of epoxide-assisted sol-gel chemistry and structural and morphological properties of the developed material.

BiVO4 Fern Architectures: A Competitive Anode for Lithium-Ion Batteries.

The development of high-performance anode materials for lithium-ion batteries (LIBs) is currently subject to much interest. In this study, BiVO4 fern architectures are introduced as a new anode material for LIBs. The BiVO4 fern shows an excellent reversible capacity of 769 mAh g-1 (ultrahigh volumetric capacity of 3984 mAh cm-3 ) at 0.12 A g-1 with large capacity retention. A LIB full cell is then assembled with a BiVO4 fern anode and LiFePO4 (LFP, commercial) as cathode material. The device can achieve a capacity of 140 mAh g-1 at 1C rate, that is, 81 % of the capacity of the cathode and maintained to 104 mAh g-1 at a high rate of 8C, which makes BiVO4 a promising candidate as a high-energy anode material for LIBs.

One-Pot in Situ Hydrothermal Growth of BiVO4/Ag/rGO Hybrid Architectures for Solar Water Splitting and Environmental Remediation.

BiVO4 is ubiquitously known for its potential use as photoanode for PEC-WS due to its well-suited band structure; nevertheless, it suffers from the major drawback of a slow electron hole separation and transportation. We have demonstrated the one-pot synthesis of BiVO4/Ag/rGO hybrid photoanodes on a fluorine-doped tin oxide (FTO)-coated glass substrate using a facile and cost-effective hydrothermal method. The structural, morphological, and optical properties were extensively examined, confirming the formation of hybrid heterostructures. Ternary BiVO4/Ag/rGO hybrid photoanode electrode showed enhanced PEC performance with photocurrent densities (J ph ) of ~2.25 and 5 mA/cm2 for the water and sulfate oxidation, respectively. In addition, the BiVO4/Ag/rGO hybrid photoanode can convert up to 3.5% of the illuminating light into photocurrent, and exhibits a 0.9% solar-to-hydrogen conversion efficiency. Similarly, the photocatalytic methylene blue (MB) degradation afforded the highest degradation rate constant value (k = 1.03 × 10-2 min-1) for the BiVO4/Ag/rGO hybrid sample. It is noteworthy that the PEC/photocatalytic performance of BiVO4/Ag/rGO hybrid architectures is markedly more significant than that of the pristine BiVO4 sample. The enhanced PEC/photocatalytic performance of the synthesized BiVO4/Ag/rGO hybrid sample can be attributed to the combined effects of strong visible light absorption, improved charge separation-transportation and excellent surface properties.

Growth study of hierarchical Ag3PO4/LaCO3OH heterostructures and their efficient photocatalytic activity for RhB degradation.

We have demonstrated the synthesis of Ag3PO4/LaCO3OH (APO/LCO) heterostructured photocatalysts by an in situ wet chemical method. From pre-screening evaluations of photocatalysts with APO/(x wt% LCO) composites with mass ratios of x = 5, 10, 15, 20, 25 and 30 wt%, we found that the APO/LCO (20 wt%) exhibited a superior photocatalytic activity for organic pollutant remediation. Therefore, an optimised photocatalyst APO/LCO (20 wt%) is selected for the present study and we investigate the effect of a mixed solvent system (H2O:THF) on the morphology, which has a direct effect on the photocatalytic performance. Interestingly, a profound effect on the morphological features of APO/LCO20 heterostructures was observed with variation in the ratio of the solvent system. From the FESEM study it is observed that the LCO spherical nanoparticles are transformed into nanorods with the variation of THF into the solvent system. Moreover, these LCO nanorods make intimate contact with the APO microstructures which is helpful for the improvement of the photocatalytic activity. The photocatalytic activities of the APO/LCO composites with different solvent ratios were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. Excellent photocatalytic activity was observed for the APO/LCO-2 (H2O : THF = 60 : 40) sample. This might be due to uniform covering of the APO microstructures by fine LCO rod-like structures offering intimate contact between the APO and LCO and providing proper channels for the degradation reactions. Furthermore, with an increasing THF volume ratio in the reaction system there was an increase of the dimensions of the LCO rod-like structures and also a loose compactness of their uniform intimate contact between the APO/LCO heterostructures. All in all, the enhanced photocatalytic activity of the APO/LCO heterostructures is attributed to the collective co-catalytic effect of LCO, by providing accelerated charge separation through the heterojunction interface, and THF, by helping to tune the unique morphological features which eventually facilitate the photocatalysis process.

Fern-like rGO/BiVO4 Hybrid Nanostructures for High-Energy Symmetric Supercapacitor.

Herein, we demonstrate the synthesis of rGO/BiVO4 hybrid nanostructures by facile hydrothermal method. Morphological studies reveal that rGO sheets are embedded in the special dendritic fern-like structures of BiVO4. The rGO/BiVO4 hybrid architecture shows the way to a rational design of supercapacitor, since these structures enable easy access of electrolyte ions by reducing internal resistance. Considering the unique morphological features of rGO/BiVO4 hybrid nanostructures, their supercapacitive properties were investigated. The rGO/BiVO4 electrode exhibits a specific capacitance of 151 F/g at the current density of 0.15 mA/cm2. Furthermore, we have constructed rGO/BiVO4 symmetric cell which exhibits outstanding volumetric energy density of 1.6 mW h/cm3 (33.7 W h/kg) and ensures rapid energy delivery with power density of 391 mW/cm3 (8.0 kW/kg). The superior properties of symmetric supercapacitor can be attributed to the special dendritic fern-like BiVO4 morphology and intriguing physicochemical properties of rGO.

Magnetically separable Ag3PO4/NiFe2O4 composites with enhanced photocatalytic activity.

Magnetically separable Ag3PO4/NiFe2O4 (APO/NFO) composites were prepared by an in situ precipitation method. The photocatalytic activity of photocatalysts consisting of different APO/NFO mass ratios was evaluated by degradation of methylene blue (MB) under visible light irradiation. The excellent photocatalytic activity was observed using APO/NFO5 (5% NFO) composites with good cycling stability which is higher than that of pure Ag3PO4 and NiFe2O4. All the APO/NFO composites showed good magnetic behavior, which makes them magnetically separable after reaction and reusable for several experiments. Photoconductivities of pure and composite samples were examined to study the photoresponse characteristics. The current intensity greatly enhanced by loading NFO to APO. Furthermore, the photocatalytic performance of the samples is correlated with the conductivity of the samples. The enhancement in the photocatalytic activity of APO/NFO composites for MB degradation is attributed to the excellent conductivity of APO/NFO composites through the co-catalytic effect of NFO by providing accelerated charge separation through the n-n interface.

Resazurin tube method: rapid, simple, and inexpensive method for detection of drug resistance in the clinical isolates of mycobacterium tuberculosis.

BACKGROUND: Tuberculosis (TB) remains a serious public health problem worldwide. The emergence of drug resistance and multidrug resistance (MDR) has become the main threat to TB treatment and control programs. Rapid detection is critical for the effective treatment of patients. In recent times, a new method using the colorimetric indicator resazurin has been proposed for drug susceptibility of Mycobacterium tuberculosis. MATERIALS AND METHODS: In this study, the resazurin reduction assay was adapted to screw cap tubes. Using the Resazurin Tube Method (RTM), a total of 100 clinical isolates were tested against Rifampicin (RIF) and Isoniazide (INH). By visual reading, the minimum inhibitory concentrations (MICs) were obtained after eight days. The results obtained were compared with the gold standard proportion method. RESULTS: Excellent results were obtained for RTM with a sensitivity of 100% for both RIF and INH, with a specificity of 98.7 and 95.3%, respectively. Kappa is the measure of agreement between the RTM and proportion method (PM) for RIF and INH, which was found to be 0.972 and 0.935 for RIF and INH, respectively. CONCLUSION: The RTM appears to be a reliable method for the rapid and simultaneous detection of MDR-TB and drug susceptibility testing (DST) of M. tuberculosis. It is simple, inexpensive, and with no biohazard risk involved.

Polymethyl methacrylate (PMMA)-bismuth ferrite (BFO) nanocomposite: low loss and high dielectric constant materials with perceptible magnetic properties.

Herein, poly(methyl methacrylate)-bismuth ferrite (PMMA-BFO) nanocomposites were successfully prepared by an in situ polymerization method for the first time. Initially, the as prepared bismuth ferrite (BFO) nanoparticles were dispersed in the monomer, (methyl methacrylate) by sonication. Benzoyl peroxide was used to initiate the polymerization reaction in ethyl acetate medium. The nanocomposite films were subjected to X-ray diffraction analysis (XRD), (1)H NMR, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), infrared spectroscopy (IR), dielectric and magnetic characterizations. The dielectric measurement of the nanocomposites was investigated at a frequency range of 10 Hz to 1 MHz. It was found that the nanocomposites not only showed a significantly increased value of the dielectric constant with an increase in the loading percentage of BFO as compared to pure PMMA, but also exhibited low dielectric loss values over a wide range of frequencies. The values of the dielectric constant and dielectric loss of the PMMA-BFO5 (5% BFO loading) sample at 1 kHz frequency was found be ~14 and 0.037. The variation of the ferromagnetic response of the nanocomposite was consistent with the varying volume percentage of the nanoparticles. The remnant magnetization (Mr) and saturation magnetization (Ms) values of the composites were found to be enhanced by increasing the loading percentage of BFO. The value of Ms for PMMA-BFO5 was found to be ~6 emu g(-1). The prima facie observations suggest that the nanocomposite is a potential candidate for application in high dielectric constant capacitors. Significantly, based on its magnetic properties the composite will also be useful for use in hard disk components.