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Environmentally, removing organic pollutants from industrial waste solutions is important. In this study, the potentiality of removing Thoron (TH) and Arsenazo III (ARZIII) pollutants was investigated using chemically stable zinc tungstate nanoparticles (ZW-NPs). The preparation of ZW-NPs was performed using an eco-friendly solvo/hydrothermal technique as a sorbent. Complete characterisation of ZW-NPs before and after the adsorption processes was performed using XRD, FT-IR, EDX, DLS, and TEM analysis. The nanostructure of the zinc tungstate and the incidence of adsorption upon the ZW-NPs were effectively demonstrated. The maximum uptakes of TH and ARZIII contaminants on the ZW-NPs sorbent were 86.3 and 94.7 mg/g respectively. These uptakes were accomplished under optimum pH of 4.0 and 5 for TH and ARZIII, respectively. The adsorption outcomes were studied using Langmuir, Freundlich, and Dubinin–Radushkevich isotherm models. Modelling results indicated that the adsorption followed a pseudo-2nd-order interaction. The adsorption isotherms and thermodynamic results demonstrated the endothermic and chemisorption behaviour. Approximately, TH and ARZIII were completely removed from the laboratory waste solutions on the studied sorbent using optimal adsorption conditions. [ABSTRACT FROM AUTHOR]

The heat capacity of zinc tungstate was determined by relaxation calorimetry in the range of ~2.6–40 K. The heat capacity was extrapolated to zero temperature, and the characteristic Debye temperature at zero temperature was determined. The experimental heat capacities presented in the literature were estimated. The values of thermodynamic functions in the range 0–301 K were refined. [ABSTRACT FROM AUTHOR]

Heterojunction combining with two kinds of different band structures semiconductors was constructed, and its photocatalytic performance could be greatly improved with the wider optical response range. The BiO2-x/ZnWO4 composite was prepared by a simple two-step hydrothermal method. The structure, morphology and optical properties of BiO2-x/ZnWO4 were characterized by XRD, SEM and UV-vis diffuse reflectometry. The photocatalytic performance and cyclic stability of BiO2-x/ZnWO4 were studied by degrading tetracycline under visible light. The results showed that with the synergistic action between BiO2-x and ZnWO4, the photo-generated carriers of BiO2-x/ZnWO4 could be effectively separated and the light absorption capacity of BiO2-x/ZnWO4 could be significantly enhanced. After 90 min of visible light illumination, the photodegradation efficiency of the composite towards tetracycline reached 86.04%, and the light response range and photocatalytic activity of the composite were better than the monomer BiO2-x and ZnWO4. In addition, the composite displayed good light stability. The capture experiments and ESR showed that h+, O2·- and ·OH were produced by the composites under light, in which h+ and O2·- were the main active substances in the process of photocatalysis, and ·OH was the minor active species, following the order of h+>O2·->·OH. It was inferred that the electron transfer mechanism of BiO2-x/ZnWO4 was Z-scheme heterojunction.

In this study, facile simultaneous nitrogen (N)-doped zinc tungstate nanorod-decorated N-doped reduced graphene oxide nanosheets (referred to as N-ZnWO4/N-rGO or N-ZWR-x) were prepared by a one-pot hydrothermal method. Here, urea serves as a structural orienting agent, a source of N, and a buffer to maintain the pH medium throughout the synthesis process. The successful formation of the crystalline nanocomposite was confirmed through X-ray diffraction, Fourier transform infrared spectroscopy, Raman, N2 physisorption, field emission scanning electron microscopy, field emission transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. The modified electrode (N-ZWR-1/GCE) was also successfully applied for the electrochemical detection of diphenylamine (DPA). It exhibited a dynamic linear range (LR: 0.2–841 μM), a limit of detection (LOD: 0.0083 μM), and an acceptable sensitivity (SEN: 1.4746 μA μM–1 cm–2) with good stability. This is due to its large surface area, mass and ionic transport, synergetic effect, and chemical stability. Moreover, this nanocomposite yields admirable reproducibility, storage stability, and selectivity and is also a promising electrocatalyst to quantify DPA in fresh fruit samples in practical analysis. [ABSTRACT FROM AUTHOR]

In this paper, ZnWO4 photocatalysts were prepared by hydrothermal method, after which IrO2 was loaded on ZnWO4 by photodeposition to synthesize IrO2/ZnWO4 composite photocatalysts. The prepared photocatalysts were characterized by XRD, SEM, TEM, XPS, and UV–Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity was investigated by inactivating bacteria in natural seawater. The effect of varying the deposition amount of IrO2 on the photocatalytic activity was investigated. The mechanism of IrO2 modification to enhance the sterilization of ZnWO4 was as follows: first, IrO2 modification significantly enhanced the effective chlorine yield of the samples. Second, IrO2 modification also promoted the charge separation efficiency of the samples. The present work confirms that photocatalytic production of effective chlorine is an important active species for sterilization in seawater systems, which provides a new idea for photocatalytic purification technology in seawater medium. [ABSTRACT FROM AUTHOR]

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Herein, zinc tungstate coupled fluorinated titanium dioxide (ZnWO4/F–TiO2) composites were synthesized by microemulsion hydrothermal process with cetyltrimethylammonium bromide/n-hexanol/deionized water/cyclohexane as microemulsion, butyl titanate as titanium source and ammonium fluoride as fluorine source. Methyl orange was used as the target pollutant in sewage to explore the photodegradation performance and recycling performance of the as-prepared specimens. Effect of coupling ratios on the photocatalytic performance was studied. SEM, XRD, UV–Vis Abs, FTIR, BET, and XPS were used to characterize the samples, the performances of photocurrent (i–t) and electrochemical impedance spectroscopy (EIS) were also investigated and the modification mechanism was systematically studied. The results showed that the optimal loading amount of ZnWO4 was 1 wt %. Under the same conditions, after illumination for 30 min with metal halide, the degradation rates of methyl orange by single TiO2, F–TiO2, and 1% ZnWO4/F–TiO2 reached 54.5, 84, and 93.5% respectively. 1% ZnWO4/F–TiO2 showed an enhanced photocatalytic activity and excellent cycle stability due to the formation of heterostructures which significantly inhibited the recombination of photogenerated electrons and holes. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are a significant class of porous, crystalline materials composed of metal ions (clusters) and organic ligands. The potential use of copper MOF (Cu-BTC) for the sonophotocatalytic degradation of Tetracycline (TC) antibiotic was investigated in this study. To enhance its catalytic efficiency, S-scheme heterojunction was created by combining Cu-BTC with Zinc tungstate (ZnWO4), employing an ultrasound-assisted hydrothermal method. The results demonstrated that the Cu-BTC/ZnWO4 heterojunction exhibited complete removal of TC within 60 min under simultaneous irradiation of visible light and ultrasound. Interestingly, the sonophotocatalytic degradation of TC using the Cu-BTC/ZnWO4 heterojunction showed superior efficiency (with a synergy index of ∼0.70) compared to individual sonocatalytic and photocatalytic degradation processes using the same heterojunction. This enhancement in sonophotocatalytic activity can be attributed to the formation of an S-scheme heterojunction between Cu-BTC and ZnWO4. Within this heterojunction, electrons migrated from Cu-BTC to ZnWO4, facilitated by the interface between the two materials. Under visible light irradiation, the built-in electric field, band edge bending, and coulomb interaction synergistically inhibited the recombination of electron-hole pairs. Consequently, the accumulated electrons in Cu-BTC and holes in ZnWO4 actively participated in the redox reactions, generating free radicals that effectively attacked the TC molecules. This study offers valuable perspectives on the application of a newly developed S-scheme heterojunction photocatalyst, demonstrating its effectiveness in efficiently eliminating diverse recalcitrant pollutants via sonophotocatalytic degradation.

Special techniques for deep purification of ZnO and WO3 have been developed in this work. A ZnWO4 single crystal has been grown by the Czochralski method using purified ZnO and WO3 chemicals, along with the ZnWO4 crystal-etalon, which has been grown at the same conditions using commercially available 5N ZnO and WO3 chemicals. The actual accidental impurities compositions of both the initial chemicals and the grown crystals have been measured by inductively coupled plasma mass-spectrometry. A complex of comparative spectroscopic studies of the crystals has been performed, including optical absorption spectra, photo-, X-ray-, and cathodoluminescence spectra and decay kinetics, as well as the photoluminescence excitation spectra. The revealed differences in the measured properties of the crystals have been analyzed in terms of influence of the accidental impurities on these properties. [ABSTRACT FROM AUTHOR]

Nanostructure-based resistive switching memory devices are being developed for low power, multilevel storage capability, extended retention capacity, and scalable devices. The zinc tungstate (ZnWO 4) nanoparticle was prepared via the facile hydrothermal method. The X-ray diffraction technique confirmed ZnWO4 monoclinic phase and crystallite nature. The scanning electron microscope was used to identify the rod-like ZnWO4 nanostructure, and further, the lattice orientation was investigated by high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy confirmed the binding states with composition of ZnWO4. Resistive switching memory based on ZnWO4 was produced and resulted in low-operating voltage. Finding new candidates for the emerging resistive memory technology is vital for the development of next-gen non-volatile memory devices and this study explored the feasibility of one of the multi-functional metal tungstate materials, ZnWO4 in the ReRAM memory application. The synthesized nanostructures are characterized to acquire the composition and bonding features which are crucial for the device performance. A non-volatile memory device based on ZnWO4 nanostructures synthesized through hydrothermal method is fabricated and the device performance is studied deliberately. [ABSTRACT FROM AUTHOR]

Zn- and W-containing oxide heterostructures have been formed by plasma electrolytic oxidation of titanium in aqueous solutions of 0.1 mol/L Na2WO4 and 0.05 mol/L Zn(CH3COO)2 with addition of organic (0.05 mol/L H2C2O4 or 0.1 mol/L CH3COOH) and inorganic (0.05 mol/L H2SO4) acids. PEO coatings have been studied by X-ray diffraction, energy dispersive analysis, and scanning electron microscopy. Depending on the acid used, the coatings contain WO3 and/or NaxWO3 and Zn0.3WO3. Annealing in air at 500–700°С leads to crystallization of WO3 and ZnWO4 in their composition. WO3 polyhedra are formed on the surface of the PEO coatings obtained in electrolytes with oxalic and sulfuric acids. Elongated ZnWO4 crystals cover the surface of coatings formed in electrolytes with acetic acid. All resulting coatings exhibit photoactivity in the degradation of indigo carmine (10 mg/L, pH 5.9) under UV irradiation. The degree of degradation is 10, 38, and 35% for PEO coatings formed in electrolytes with the addition of CH3COOH, H2C2O4, and H2SO4, respectively. The photocatalytic activity of the samples can be regulated by controlling the shape, size, and composition of microcrystals growing on the surface of PEO coatings during annealing. [ABSTRACT FROM AUTHOR]

It is important to reduce costs and improve performance by microstructure-control of materials. The direct precipitation method and hydrothermal method were adopted to adjust the crystallinity of zinc tungstate (ZnWO4) pigments. Correlation between the crystallinity of ZnWO4 and its anti-corrosion performance is explored. The results confirm that ZnWO4 crystals prepared by hydrothermal reaction for 12 h have high crystallinity, and the corrosion resistance is enhanced by 737.0% compared with blank coating in the epoxy resin system. The improvement in corrosion inhibition is due to the enhancement of the shielding effect of the multilayer passivation film and electronic suppression effect resulted from the high ZnWO4 crystallinity. The low ZnWO4 crystallinity can weaken the corrosion resistance because of the defect-enriched effect. Advancement in anticorrosive performance by crystallinity-control meets the reduction of costs and energy consumption in the coatings industry. The correlation between the crystallinity of ZnWO4 and its anti-corrosion performance is discovered. ZnWO4 crystals prepared by hydrothermal method for 12 h have high crystallinity. The corrosion resistance is enhanced by 737.0% compared with blank coating in the epoxy resin system. The improvement in corrosion resistance originated from the enhancement of the shielding effect of the multilayer passivation film and electronic suppression effect resulting from the high ZnWO4 crystallinity. [ABSTRACT FROM AUTHOR]

Flexible photodetectors hold significant interest across diverse applications, such as imaging, communication, healthcare, and environmental monitoring. This work reports a broad-band photodetector comprising Zinc tungstate (ZW) and Cobalt tungstate (CW) on a flexible paper substrate. CW thin film was fabricated by a facile successive ionic layer adsorption and reaction(SILAR) technique and the ZW nanoparticles, synthesised via simple co-precipitation method, were drop casted on it to form a heterojunction. Structural characterization of the materials was conducted using X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR), while scanning electron microscopy was employed for detailed morphology analysis. CW is a p type semiconductor with its bandgap of 2.6 eV, exhibits impressive sensitivity across both visible and infrared segments of the electromagnetic spectrum. In contrast, ZW which is n type contributes UV-responsive, attributes effectively broadening the overall spectral sensitivity from Ultraviolet (UV) to Infrared (IR) spectra within a single compact device. The photodetector demonstrates remarkable responsivity of 1.66 mA/W (UV), 24.58 mA/W (Visible), and 0.024 mA/W (IR) under respective light intensities of 0.6 mW/cm², 0.4 mW/cm², and 4.41 mW/cm. The detectivity metrics are equally impressive, measuring at 9.9×1010 Jones (UV), 5.01×1011 Jones (Visible), and 4.48×1010 Jones (IR). The successful combination of Zinc tungstate and Cobalt tungstate on a paper substrate represents an advancement in photodetector technology, offering enhanced sensitivity, extended spectral range, and the potential for seamless integration into wearable electronics and portable devices. [Display omitted] • The photodetector comprises Zinc tungstate and Cobalt tungstate fabricated on paper substrate. • CW thin film was fabricated using SILAR technique while ZW nanoparticles were drop-casted onto it. • CW exhibits sensitivity across visible and infrared regions while ZW contributes UV-responsive attributes • The photodetector demonstrates remarkable responsivity and detectivity metrics across different light intensities and spectral ranges. [ABSTRACT FROM AUTHOR]

[Display omitted] • A lead-free FPENG was developed based on a novel ZnO–ZnWO 4 @PDMS. • The incorporation of ZnWO 4 with ZnO exhibited an excellent synergistic effect. • The piezoelectric response of the composite is 1.32 V (∼4 times better than ZnWO 4). • With finger tapping motion, a 1 μF capacitor is charged within 56 s and powered LED. • Real-time early safety warning alarm system was demonstrated. With the rapid development of research world, the number of researchers and research laboratories is increasing rapidly. Simultaneously, accidents in laboratories are on the rise, drawing significant attention from everyone. To address this issue, the current study demonstrates a real-time safety early warning alarm system aimed at preventing accidents and enhancing safety management in laboratories. We developed a zinc tungstate nanoparticles (NPs) integrated on zinc oxide hexagonal microdiscks (h -MDs) (ZnO–ZnWO 4 @PDMS) composite based on a novel flexible piezoelectric nanogenerator (FPENG). The observed piezoelectric response was 1.32 V, which is ∼4 times better than that of pure ZnWO 4 , owing to the synergistic effect of ZnO–ZnWO 4 @PDMS. When subjected to finger-tapping motion, the FPENG can charge a 1 μF capacitor, and it reached 81 mV within 56 s. Subsequently, the light-emitting diodes (LEDs) are powered with amplification. The FPENG system was demonstrated and validated through real-time application in the laboratory setting, marked as a "caution/restricted" line. The application of the system demonstrated its capability to simultaneously illuminate LEDs and sound alarms when people touch or cross the caution line. Furthermore, the proposed FPENG exhibited ∼660 mV even ∼90 % humidity, with no noticeable electrical changes under different solvents, confirming that the proposed FPENG is not affected by varying humidity and various indoor conditions. These outstanding results and real-time demonstrations unequivocally establish the feasibility of this system in contexts such as bank lockers, metro systems, hilly areas, and more. [ABSTRACT FROM AUTHOR]

Herein, we are reporting the synthesis and characterization of polythiophene (PTh) and its novel nanocomposites with zinc tungstate (ZT) and graphene/zinc tungstate (G/ZT) hybrid for Direct current (DC) electrical conductivity based cigarette smoke sensing at room temperature. X-ray diffraction, Fourier-transform infrared, Raman, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy and thermogravimetric analysis techniques were used for the characterization of the as-prepared materials. The results showed that the DC electrical conductivity and sensing performance of PTh significantly improved by incorporation of ZT and G/ZT into it. PTh/G/ZT-3 (i.e. PTh/G/ZT nanocomposite containing 15 wt% G/ZT) was found to be the best sensor in terms of sensing response (81.5%) and reversibility (90.55%) along with the most stable semiconductor under isothermal and cyclic ageing conditions. Sensing response of PTh/G/ZT-3 was also tested in the exposure to various components of cigarette smoke (namely ammonia, carbon dioxide, ethanol, formaldehyde, acetone, benzene, toluene, phenol) and the highest sensing response was observed in the exposure to ammonia. The significant increase in conductivity of PTh/G/ZT nanocomposites was explained by the transfer of polarons from PTh to graphene, that is, creation of a hole in graphene where they achieved rapid mobility along with the extended π-conjugated system. Finally, a sensing mechanism was proposed through adsorption–desorption of cigarette smoke on the surface of PTh/G/ZT where electronic interactions between polarons of PTh and various components of cigarette smoke (mainly ammonia and ethanol) affected the change in DC electrical conductivity. [ABSTRACT FROM AUTHOR]

Nano-sized and micro-sized ZnWO4 powders were obtained by different methods: hydrothermal synthesis with microwave heating, molten salt method, solid-state synthesis and сrushing of bulk crystals. Their morphological features were studied using transmission electron microscope and scanning electron microscope. The obtained nano- and micro-sized powders were used as fillers for flexible composite scintillators. The silicon rubber was used as a binder. The luminescent characteristics and scintillation performance of composite scintillators were measured. The dependence of scintillation performance of flexible scintillators on the morphological features of ZnWO4 nanocrystallites was demonstrated. The flexible composite scintillator based on zinc tungstate obtained by solid-state synthesis with lithium nitrate addition was obtained and investigated. Its scintillation performance was close to that of a ZnWO4 single crystal.

Graphene oxide decorated ZnWO 4 (GO-ZnWO 4) nanocomposite was synthesized by hydrothermal route and characterized using X-rays diffractometry (XRD), scanning electron microscope (SEM), energy dispersive x-rays (EDX), UV–Vis and particle size analyzer. The GO-ZnWO 4 composites were in pure crystalline phase with average particle size of 30 nm, spherical and uniformly distributed having band gap value of 3.13 eV. The photocatalytic activity (PCA) was monitored by degrading cetirizine hydrochloride (C-HCl) under UV irradiation. The process variables were optimized through response surface methodology (RSM) and at optimum conditions, up to 89% degradation of C-HCl was achieved and the RSM model (R2 = 0.98) showed a satisfactory correlation between the experimental and predicted response for the degradation of C-HCl. The hydrothermal route employed was efficient to prepare GO-ZnWO4 nanocomposite and this class of catalysts might be active photocatalyst for the degradation of pharmaceutical agents in the industrial wastewater. Unlabelled Image • Graphene oxide decorated ZnWO4 composite was synthesized by hydrothermal route. • SEM, XRD, EDX and UV–Vis techniques were employed for characterization. • Photocatalytic performances were evaluated by degrading cetirizine dihydrochloride. • The conditions were optimized using response surface methodology. • Graphene oxide decorated ZnWO4 composite proved to be potential photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract The enhancement of photoluminescence of alkali metal sulfate-doped zinc tungstate was investigated. All samples were prepared by solid-state reaction at 800 °C using ZnO, WO 3 , and alkali metal sulfates as starting powders. The zinc tungstate phase was confirmed from the samples by X-ray diffraction. The emission peak of the samples excited at 275 nm was observed at 465 nm. Rb 2 SO 4 > K 2 SO 4 > Cs 2 SO 4 > undoped > Na 2 SO 4 > Li 2 SO 4 was the order of peak emission intensity of alkali metal sulfate-doped samples. Alkali metals with a large ionic radius (K, Rb, Cs) enhanced the emission of intrinsic luminescence in the blue wavelength region. Moreover, sulfates had the potential to change the luminescence activities of the samples. [ABSTRACT FROM AUTHOR]

ZnWO4 nanoparticles were synthesized by a facile sol-gel method using Zn(CH3COO)2 and Na2WO4. The as-prepared ZnWO4 was characterized by several techniques: XRD, FTIR, TEM, FESEM, EDS, BET, PL and DRS. The effects of pH and calcined temperatures were investigated on the crystal structure of the ZnWO4 photocatalyst. Results showed that pure ZnWO4 was synthesized in pH 6 and calcined temperature 500 °C for 5 h. The synthesized ZnWO4 nanoparticles have a mean diameter less than 100 nm and the bond gap energy are about 3.20 eV. ZnWO4 nanoparticles showed efficient photocatalytic activity for the degradation of methylene blue under ultraviolet light irradiation. The apparent rate constant (k) of photodegradation reaction was obtained as 1.62 × 10−2 min−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-MOF based S-scheme Cu-BTC/ZnWO 4 heterojunction was fabricated. • Tetracycline was completely removed by Cu-BTC/ZnWO 4 within 60 min of sonophotocatalysis. • Photogenerated charge carrier separation is accelerated by the S-scheme heterojunction. • High stability and reasonable reuse potential were shown by the catalyst. • Demonstrated unprecedented efficacy in destroying tetracyline from hospital effluent water. Metal-organic frameworks (MOFs) are a significant class of porous, crystalline materials composed of metal ions (clusters) and organic ligands. The potential use of copper MOF (Cu-BTC) for the sonophotocatalytic degradation of Tetracycline (TC) antibiotic was investigated in this study. To enhance its catalytic efficiency, S-scheme heterojunction was created by combining Cu-BTC with Zinc tungstate (ZnWO 4), employing an ultrasound-assisted hydrothermal method. The results demonstrated that the Cu-BTC/ZnWO 4 heterojunction exhibited complete removal of TC within 60 min under simultaneous irradiation of visible light and ultrasound. Interestingly, the sonophotocatalytic degradation of TC using the Cu-BTC/ZnWO 4 heterojunction showed superior efficiency (with a synergy index of ∼0.70) compared to individual sonocatalytic and photocatalytic degradation processes using the same heterojunction. This enhancement in sonophotocatalytic activity can be attributed to the formation of an S-scheme heterojunction between Cu-BTC and ZnWO 4. Within this heterojunction, electrons migrated from Cu-BTC to ZnWO 4 , facilitated by the interface between the two materials. Under visible light irradiation, the built-in electric field, band edge bending, and coulomb interaction synergistically inhibited the recombination of electron-hole pairs. Consequently, the accumulated electrons in Cu-BTC and holes in ZnWO 4 actively participated in the redox reactions, generating free radicals that effectively attacked the TC molecules. This study offers valuable perspectives on the application of a newly developed S-scheme heterojunction photocatalyst, demonstrating its effectiveness in efficiently eliminating diverse recalcitrant pollutants via sonophotocatalytic degradation. [ABSTRACT FROM AUTHOR]

The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 μm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.

Brick-shaped zinc tungstate nanoparticles have been synthesized by ecofriendly solvent-free process using molten salts. Zinc tungstate nanobricks (ZnWO4 Nbs) were characterized by powder x-ray diffraction (PXRD), FTIR, Raman, energy dispersive and electron microscopic studies. ZnWO4 Nbs are used as the multifunctional electrode materials to oxygen generation reactions (OGR), oxygen reduction reactions (ORR) and supercapacitors (SCs) as well as photo-catalysts in the waste-water treatment by the degradation of organic dyes. Low overpotential (ƞ10 = 0.475 V), low tafel slope (140 mV/dec), high current density (~70 mA/cm2) and good stability of the electrodes are the key results of the present studies for water electrolysis (OGR/ORR). ZnWO4 Nbs have also shown great interest in supercapacitors with efficient charge-discharge activities in 1 M KOH. The specific capacitance and energy density of ZnWO4 Nbs were found to be 250 F/g and 80 Wh/kg, respectively, at 5 mV/s, these values are relatively higher than that of previously reported specific capacitance and energy density value of metal tungstate nanoparticles. ZnWO4 Nbs as the photo-catalysts work very significantly for photocatalytic degradation of aqueous MB dye solution (~85 % in 3 h) in neutral medium.ZnWO4 Nanobricks show significant multifunctional electro-chemical activities in alkaline medium and photocatalytic degradation of organic dye in neutral medium. Ecofriendly solvent-free Synthesis of ZnWO4 Nanobricks (Nbs).ZnWO4 Nbs show admirable multifunctional electrochemical activities (OGR/ORR/SCs).Low overpotential, low Tafel values, relatively high current density and good stability of electrode materials are significant for OGR and ORR.ZnWO4 Nbs exhibit efficient supercapacitor performances with the specific capacitance (250 F/g) and energy density (80 Wh/kg) at 5 mV/s in 1 M KOH.ZnWO4 Nbs also work as photo-catalysts to enhance the degradation of aqueous organic dyes. [ABSTRACT FROM AUTHOR]

In this work, we found the significant improvement of photoluminescence of zinc tungstate doped with potassium salts. The samples were prepared by solid-state reaction using ZnO, WO 3 , KNO 3 , K 2 SO 4 , and KCl as starting powders. The powders were mixed with the molar ratios of ZnO: WO 3 : potassium salts = 1: 1: x and sintered at 800 °C for 3 h in air. The emission peak of photoluminescence excited at 275 nm was observed at 465 nm. With increasing potassium salts content, the intensity increased reached its maximum at x = 0.02 and decreased. The tendency of the luminescence intensity for KCl doping was almost the same as KNO 3 doping, whereas, for K 2 SO 4 doping, the tendency of the decrease was less steep than other doping. The order of each maximum intensity was KNO 3 >K 2 SO 4 >KCl. It was considered that K replacing Zn in the crystal lattice enhanced the intrinsic luminescence in the blue wavelength region. Moreover, different anions doping had the different effect of the enhancement of the luminescence. [ABSTRACT FROM AUTHOR]

Polycrystalline samples in the lutetium-doped zinc tungstate system ZnLuWO with 0 ≤ x ≤ 0.08 were synthesized using the coprecipitation method followed by thermal treatment at 1000 °C during 4 h. The polycrystalline samples were characterized by X-ray diffraction analysis, scanning electron microscopy (SEM), infrared spectroscopy, and luminescence analysis under X-ray excitation. Rietveld analyses were performed. The variation of the wolframite structure cell parameters in the range 0 ≤ x ≤ 0.05 were congruent with substitution of Zn by Lu. SEM micrographs of the obtained samples presented improved crystallization with morphology depending on the lutetium fraction. The luminescence spectra obtained under X-ray excitation ( E < 40 keV) were in the blue-green region, and their intensity increased with x up to x = 0.05. The differences in the intensities of the X-ray luminescence spectra could be related to additional cation vacancies resulting from substitution of Zn by Lu. [ABSTRACT FROM AUTHOR]

ZnWO4 hierarchical hexangular microstars (HHMs) composed of crossed microplatelets were synthesized by a two-step hydrothermal reaction without using any surfactants. The homogeneous HHMs were characterized by TEM/SEM and XRD to reveal the structural features and crystallographic phase. On the basis of the analysis of the time-dependent evolution of ZnWO4 HHMs, a mechanism of in-situ formation and crystallographic fusion, wherein the morphology, components, and phase changed, is proposed to explain the formation process of 3D hexagonal structures. Furthermore, calcined ZnWO4 HHMs were evaluated as anode material for lithium-ion batteries, and exhibited better rate capabilities and cycling performance than the as-synthesized material. This can be attributed to the stabilized and highly crystalline structure as well as the synergic and interfacial effects between different metal ions, which relieve the volume change during the charge/discharge process and provide more active sites for lithium-ion storage. The synthetic method and growth mechanism could be applied to design and synthesize other hierarchical structures. [ABSTRACT FROM AUTHOR]

The discharge of wastewater containing hexavalent chromium (Cr(VI)) would cause serious environmental pollution and endanger human health. Design of high-performance and stable photocatalysts for Cr(VI) reduction in neutral solution remain huge challenging. Herein, a novel starfish-like zinc tungstate/zinc benzoate (ZnWO 4 /Zn(Bro) 2) inorganic/organic heterojunction photocatalyst was synthesized via a facile hydrothermal method. The starfish-like zinc tungstate was decorated with uniform dispersed zinc benzoate nanosheets via a self-assembling process, The intimate interface between inorganic and organic phase significantly boosted the transport efficiency of photogenerated carriers and reduced the recombination probability of e- and h+, and enhanced the photocatalytic efficiency for Cr(VI) reduction. the optimized ZWBR-2 composite catalyst displayed conspicuous photocatalytic activity and stability towards the Cr(VI) reduction in neutral solution. This work gives a new perspective to design efficient and promising inorganic/organic heterojunction photocatalyst used in dealing with Cr(VI) in neutral solution. [Display omitted] • Novel starfish-like ZnWO 4 /Zn(Bro) 2 inorganic/organic heterojunction was synthesized by a facile hydrothermal process. • The intimate interface between ZnWO 4 and Zn(Bro) 2 profoundly boosted the transport efficiency of photogenerated carriers. • ZnWO 4 /Zn(Bro) 2 showed conspicuous photocatalytic activity and stability towards Cr(VI) reduction in a neutral environment. [ABSTRACT FROM AUTHOR]

Zinc tungstate–carbon nanoparticles were synthesized by a one-step hydrothermal process followed by heat treatment. X-ray diffraction results indicated that the addition of glucose prevented grain growth of zinc tungstate during the hydrothermal process and subsequent heat treatment. Transmission electron microscopy images showed that the zinc tungstate nanoparticles were coated by carbon with a thickness of 1 nm following heat treatment at 550°C and a diameter of 10 nm with a homogeneous morphology. Electrochemical measurements showed that the zinc tungstate–carbon nanoparticles reached an initial discharge capacity of 990 mAh g−1at a current density of 50 mA. g−1. The specific capacity of the zinc tungstate-carbon nanoparticles was maintained at approximately 400 mAh g−1after 50 cycles, exhibiting better stability than pure zinc tungstate due to the carbon coating providing high conductivity with the zinc tungstate nanoparticle. [ABSTRACT FROM AUTHOR]

Nanosized Zn–WO 3 and ZnWO 4 materials have been prepared by microwave irradiation method. The physico-chemical characterization of the prepared nanomaterials was carried out by X-ray diffraction (XRD) and high resolution-scanning electron microscopy (HR-SEM) techniques. The size and shape of the ZnWO 4 material can be controlled by changing the temperature. The XRD analysis revealed the formation of monoclinic phase of the calcined nanopowder. The HR-SEM images showed the sphere and plate shape particles. The electrochemical behavior of the ZnWO 4 modified electrodes was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) techniques. The synthesized material shows the pseudocapacitance. The specific capacitance of 35.70 F/g was achieved for the Zn–WO 3 nanopowder. [ABSTRACT FROM AUTHOR]

Highlights: [•] An increase of light output was detected in Zn x Mg1−xWO4 with maximum at x =0.5. [•] Numerical simulation of the relaxation of hot electrons and holes was performed. [•] Distance between relaxed charge carriers depend on x and influence light output. [Copyright &y& Elsevier]

Abstract: The process of energy transfer to the emission centers is studied in ZnWO4 and ZnWO4:Mo single crystals in the temperature range 10–300K. A numerical simulation describing the process is presented; the temperature dependence of energy transfer efficiency to the intrinsic emission centers in ZnWO4 is shown to be defined by the modification of Onsager sphere radius. A competitive role of radiative relaxation channel related to the impurity of molybdenum is studied in ZnWO4:Mo. It is shown that below 60K the energy transfer to the MoO6 emission centers by free charge carriers terminates due to the self-trapping of holes at WO6 complexes. [Copyright &y& Elsevier]

Highlights: [•] ZnWO4 nanoparticles were synthesized via a novel electrodeposition method. [•] Taguchi statistical method was used for optimization of electrosynthesis parameters. [•] Composition and structural properties of ZnWO4 nanoparticles were studied. [•] ZnWO4 nanoparticles were characterized by XRD, SEM, UV, FT-IR, and photoluminescence. [Copyright &y& Elsevier]

Highlights: [•] ZnWO4/Bi2WO6 photocatalyst can be synthesized by one-step hydrothermal method. [•] Synthesizing suspension with pH 7 favors the formation of ZnWO4 and Bi2WO6 phases. [•] Bi2WO6 nanoparticles are separate and/or attached to the surface of ZnWO4 particles. [•] Composite photocatalyst with 30mol% Bi3+ ion shows higher photocatalytic activity. [•] The n-n isotype junction and charge separation of each semiconductor have effect. [Copyright &y& Elsevier]

In the present paper, we report low frequency ac conductivity and dielectric studies on the composites of conducting polyaniline (PANI) with crystalline zinc tungstate (ZnWO4) powder. These composites have been synthesized by single step in situ polymerization technique by placing fine grade powder of ZnWO4 during the polymerization of aniline. The composites thus formed were characterized by FTIR spectra and scanning electron microscopy (SEM), which conforms the presence of ZnWO4 in polyaniline matrix and the formation of the composite. AC conductivity and dielectric response of these composites were investigated in the frequency ranging from 50 Hz to 5 MHz. it was found that the ac conductivity obeyed the power law index, where the ac conductivity increases with frequency. PANI/ZnWO4 composites have shown high dielectric constant, which could be related to conductivity relaxation phenomenon. It is observed that both dielectric constant and dielectric loss have decreased with increase in frequency. Variations in measured parameters of AC response with increase frequency of the composites follow systematic trends that are similar to those observed with decreasing temperature and level of doping. [ABSTRACT FROM AUTHOR]

Reactivity in the solid-state between ZnWO4 and some RE2MoO6 ( RE=Y, Sm, Eu, Gd, Dy, Ho, Er and Lu) was investigated by XRD and DTA-TG methods. Four new compounds with the formula ZnRE2MoWO10 ( RE=Sm, Eu, Gd, Dy) were synthesized. The obtained compounds are isostructural and crystallize in the monoclinic system. They melt incongruently within the temperature range of 1016–1033°C. The solid product of melting is an adequate of rare-earths molybdate. [ABSTRACT FROM AUTHOR]

A high light yield at low temperatures is one of the key criteria in the choice of scintillating target crystals for the CRESST-II Dark Matter search. We perform a feasibility study on ZnWO4 crystals as scintillating targets for the CRESST-II experiment. The light yield and the quenching factors of ZnWO4 at mK temperatures are given for the first time. [ABSTRACT FROM AUTHOR]

Monoclinic ytterbium-lithium codoped zinc monotungstate crystal (Yb3+,Li+:ZnWO 4) is a promising material for laser opertation at ~1.06 μm. Absorption, σ abs , and stimulated-emission, σ SE , cross-sections are determined for light polarized along the optical indicatrix axes, E || N p , N m and N g. At room temperature, the maximum σ SE amounts to 2.81 × 10−20 cm2 at 1055.6 nm (for E || N p) and the gain bandwidth reaches ~22 nm (for E || N g). The radiative lifetime of the upper laser level is 0.37 ms. The Stark splitting of Yb3+ multiplets is resolved with low-temperature (6 K) spectroscopy revealing a relatively large total splitting of the ground-state, Δ E (2F 7/2) = 804 cm−1, being remarkably high as compared to other Yb3+-doped tungstate crystals. A notable inhomogeneous broadening of the zero-phonon line is detected at 6 K. A continuous-wave diode-pumped 1.8 at.% Yb3+,Li+:ZnWO 4 laser generated a maximum output power of 2.90 W at ~1059 nm with a slope efficiency of 57.9% and a linearly polarized output ( E || N p). Yb3+,Li+:ZnWO 4 is attractive for broadly tunable and mode-locked oscillators. • Monoclinic ytterbium-lithium codoped zinc monotungstate crystal (Yb3+,Li+:ZnWO 4). • Absorption and stimulated-emission cross-emission cross-sections for polarized light. • The maximum σ SE is 2.81 × 10−20 cm2 at 1055.6 nm and the gain bandwidth reaches ~22 nm. • The Stark splitting of Yb3+ multiplets resolved with low-temperature spectroscopy. • Diode-pumped laser generated 2.90 W at ~1059 nm with a slope efficiency of 57.9%. [ABSTRACT FROM AUTHOR]

Zinc tungstate is an inorganic material which shows immense potential in diverse areas such as photoluminescence, sodium-ion batteries, and catalysis. Thus, the synthesis and characterization of ZnWO 4 by ultrasonic spray pyrolysis using different heat treatments (between 750 °C and 1000 °C) is reported herein. X-ray diffraction and Raman spectroscopy were used to confirm the formation of the ZnWO 4 with wolframite-type monoclinic structure. Scanning electron microscopy images revealed that the ZnWO 4 particles have a microsphere-like morphology formed by the junction of different nanocrystals and its surface changed by heat treatment. The bandgap energies had a small variation among the samples (3.88 eV–3.98 eV). The photoluminescence emission of the samples showed a broadband spectrum with white light, in which structural alterations occurred with the increase in the heat treatment, which also increased the emission intensity and broadband. The samples synthesized at 950 °C and 1000 °C showed to be promising warm- and neutral-white light emission sources. • ZnWO 4 samples were obtained with success by ultrasonic spray pyrolysis. • Heat treatment modifications provoked structural and morphological alterations. • Photoluminescence spectra were influenced by change structural. [ABSTRACT FROM AUTHOR]