Silver Tungstate Research Articles

Sonochemical synthesis and characterization of silver tungstate nanostructures as visible-light-driven photocatalyst for waste-water treatment

Highly active nanostructured silver tungstate for visible-light-driven photocatalysis is fabricated via an effortless and quick sonochemical pathway. Role of capping agent kind, concentration of tungsten source and time of sonication as efficacious variables has been explored for fabrication of silver tungstate through sonochemical pathway. The outcomes denoted successful fabrication of homogeneous silver tungstate nanoparticles with fine size in optimal circumstance (30 min of sonication, usage of SDBS and 0.01 mol of tungsten source). As-fabricated photocatalyst, the nanostructured silver tungstate has been identified with the aid of multiple techniques. The created silver tungstate micro/nanostructures employed to degrade diverse contaminants beneath visible light. Degradation yield of 94.23% for Acid red 14 and 96.31% for eriochrome cyanine R and 100% for Rhodamine B has been obtained with the help of the nanostructured silver tungstate (created in optimal circumstance) within 60 min. Further, nanostructured silver tungstate could completely destruct 2-naphthol within 15 min. No considerable decrement in performance was seeable within re-utilized experiments. The easy, effortless and quick fabrication of highly active nanostructured silver tungstate for visible-light-driven photocatalysis through sonochemical pathway may contribute efficient in environmental remediation.

Dual enzyme-like properties of silver nanoparticles decorated Ag2WO4 nanorods and its application for H2O2 and glucose sensing

The facile one-pot hydrothermal synthesis of silver nanoparticles decorated silver tungstate nanorods (Ag@Ag2WO4 NRs) and their catalytic activities similar to those of natural enzymes catalase and peroxidase were reported. The Ag@Ag2WO4 NRs could catalyze the decomposition reaction of H2O2 into water and oxygen besides catalyzing the reduction of H2O2 into water in the presence of peroxidase substrates. Spectrophotometric and electrochemical methods were used to investigate the pH-dependent dual enzyme mimics exhibited by Ag@Ag2WO4 NRs. The Ag@Ag2WO4 NRs showed a lower Km value when compared to the natural horseradish peroxidase enzyme showing the stronger affinity for hydrogen peroxide and TMB. The peroxidase-like property of the synthesized Ag@Ag2WO4 NRs was exploited to develop a H2O2 sensor with a broad linear range and low detection limit. Thus, a wide linear range of 45.4 μM- 2.38 mM and a low detection limit of 5.4 μM was obtained by spectrophotometry while a wide linear range of 62.34 μM- 2.4 mM and a low detection limit of 6.25 μM was obtained by amperometry for H2O2. Further, the detection method was extended for the detection of glucose with a wide linear range of 27.7 μM- 0.33 mM and a low detection limit of 2.6 μM.

In Vitro Toxic Effect of Biomaterials Coated with Silver Tungstate or Silver Molybdate Microcrystals

Purpose. This study evaluated the cytotoxicity of antimicrobial silver tungstate (Ag2WO4) or silver molybdate (Ag2MoO4) microcrystals coating biomaterials. Materials and Methods. The coating procedure was performed onto titanium, zirconia, and acrylic resin specimens. Eluates of the coated specimens were obtained, which were used for cytotoxicity analyses, including Alamar Blue, MTT, and CytoTox-ONE tests. Data were analyzed using two-way ANOVA, followed by the Tukey test (α = 0.05). The results of each experimental group were also compared to those of the control of living cells, taken as 100% cell viability. Results. In general, it was observed that the percentage of living cells from all biomaterials coated with both microcrystals was statistically different compared to the ones from the uncoated sample groups, except for the results from MTT of specimens of Ti coated with α-Ag2MoO4. All uncoated biomaterials were classified as noncytotoxic by the three assays used in the present study. It was observed that the microcrystals in solution were strongly cytotoxic, with death of almost 100% of cells, from the analysis of the results of the Alamar Blue assay. Conclusion. The most biomaterials coated with both microcrystals showed some degree of cytotoxicity in the different assays. The results described herein should be seen as an alert to the use of microcrystals, which can expose patients to health risks.

Visible light-assisted photodegradation by silver tungstate-modified magnetite nanocomposite material for enhanced mineralization of organic water contaminants

The modification of silica-coated magnetite nanoparticles with silver tungstate has been reported to form an effective heterogeneous photo-Fenton catalyst (Fe@AgW) for wastewater treatment. The prepared nanocomposite was analyzed and characterized with the help of SEM, TEM, Powder XRD, BET, UV-DRS, and FT-IR spectroscopy. The nanocatalyst was successfully investigated for mineralization of model cationic and anionic dyes representing industrial effluents pollution and colorless pollutant bisphenol A. The degradation of methylene blue (MB) and methyl orange (MO) was up to 92% and 82%, respectively, using Fe@AgW nanocomposite as a photo-Fenton catalyst. The nanocatalyst was also tested against pathogenic bacterial strains to explore its broad-spectrum use for water treatment. The material owns its desired properties such as economic, high efficiency, simple reaction conditions, and effortless magnetic separation for its potential broad scope applicability in water treatment.

Ultrasonic assisted fabrication of silver tungstate encrusted polypyrrole nanocomposite for effective photocatalytic and electrocatalytic applications

Ultrasonication is an emerging and evergreen technique for the efficient synthesis of the catalytically active heterostructured materials. In-situ one-pot ultrasonic-assisted synthesis method was demonstrated in this work for the fabrication of silver tungstate encrusted polypyrrole nanocomposite using semi-automatic ultrasonic probe maintained at 34°C/50kHz ultrasonic frequency and at 150W ultrasonic power. This material retains enhanced optical, electrical, morphological properties, photocatalytic behavior in photodegradation of congo red dye, tetracycline drug and its electrochemical sensing potential for the effective determination of a broad spectrum of antibacterial drug, nitrofurazone. Optical properties were investigated using UltraViolet-Visible diffuse reflectance spectral (UV-VIS DRS) data along with Tauc's bandgap energy calculations. The morphological properties were examined using FESEM and TEM micrographs. All the PXRD and XPS details prove the effective distribution of PPy on the surface of Ag2WO4 rods with the help of powerful ultrasonic assistance. PPy acted as a support for nucleation and growth of Ag2WO4 and an inhibitor of phase transformations. Ag2WO4/PPy exhibits great photocatalytic behavior while comparing with pure PPy and Ag2WO4 in the degradation of carcinogenic dye congo red and antibiotic drug tetracycline. In addition to that, Ag2WO4/PPy modified GCE exposed a widespread linear range from 0.1 to 107µM along with a very low detection limit of 12nM and huge sensitivity of 1.74 µA µM-1cm-2 in the electrochemical determination of nitrofurazone.

Ag2WO4 nanoparticles radiolabeled with technetium-99m: a potential new tool for tumor identification and uptake

Silver tungstate nanoparticles have been presenting attractive characteristics that could allow its usage in the biomedical sciences. In this study, Ag2WO4 nanoparticles with an average size of 242 nm were obtained and radiolabeled with technetium-99m with high labeling-yield as well as high stability. Biodistribution studies were carried out in healthy and tumor-bearing mice to determine the nanoparticle’s in vivo behavior. The results revealed an important tumor-to-muscle ratio, reaching values above than 1.5, demonstrated the ability of this nanomaterial in accumulating preferentially in tumor tissue. All results together, converge to consider the Ag2WO4 nanoparticles as a potential system against cancer and a potential new radiolabeled probe for tumor identification and uptake.

Doping of silver vanadate and silver tungstate nanoparticles for enhancement the photocatalytic activity of MIL-125-NH2 in dye degradation

Recently, the increment in environmental pollution has challenged the investigation of photocatalytic systems. However, metal organic framework MOFs have superior photocatalytic action, it exhibits low efficiency of light energy because of their large effective band gap. Hence, the current study presents an innovative strategy for enhancing the photocatalytic activity of Ti-containing MOF (MIL-125-NH2) by doping of silver vanadate (Ag3VO4) and silver tungstate (Ag2WO4) nanoparticles. For the prepared composites, spherical nanoparticles of Ag3VO4 and Ag2WO4 were deposited on size regulated microcrystals of MIL-125-NH2. After doping of Ag2WO4 and Ag3VO4, the optical band gap of MIL-125-NH2 was decreased from 2.65 eV to 2.56 eV and 2.27 eV, respectively. The effect of doped nanoparticles on the photocatalysis of MIL-125-NH2 was monitored in the degradation reaction of Methylene Blue (MB) and Rhodamine B (RhB) dyes under UV and Visible light. The degradation of dyes (MB & RhB) was significantly enhanced by doping of nanoparticles. The rate of dye degradation (k1) was accelerated by factor of 1.6–2.1 and 2.1–4.9 due to doping of Ag2WO4 and Ag3VO4, respectively. Ag3VO4@MIL-125-NH2 exhibited the highest photocatalytic activity logically due to the lowest band gap. The efficiency of Ag3VO4@MIL-125-NH2 as photocatalyst was reduced by only 25.9–31 % after 5 regeneration cycles. The prepared composites are promising to apply as recyclable photocatalysts in the degradation of dyes in the sunlight, able to reuse for many cycles with substantial degradation efficiency.

Antimicrobial properties of α-Ag2WO4 rod-like microcrystals synthesized by sonochemistry and sonochemistry followed by hydrothermal conventional method.

In this study we report the synthesis of silver tungstate microcrystals (α-Ag2WO4) by sonochemistry method (SC) at 65 °C and sonochemistry followed by conventional hydrothermal (SC + HC) for 1, 6 and 12 h, at 140 °C. The structural characterization by XRD confirms the alpha phase of the orthorhombic structure and the space group Pn2n, for all synthesized microcrystals. All the actives modes identified at the Raman spectroscopy were characteristic of alpha phase. The optical band gap by UV-Vis spectroscopy using the diffuse reflectance were 2.98, 3.0, 2.99 and 2.96 eV, for the microcrystals SC, SC + HC-1 h, SC + HC-6 h and SC + HC-12 h, respectively. FE-SEM images show the rod-like microcrystals, however, exhibiting the plane surface (1 0 1) only for the synthesized microcrystals with the assistance of the hydrothermal method (SC + HC-1 h, SC + HC- 6 h and SC + HC-12 h). The antimicrobial potential was confirmed for all α-Ag2WO4 microcrystals synthesized. However, the SC + HC-12 h microcrystals were more susceptible in the bacterial and fungal inhibition, with MIC values for microorganisms C. albicans, T. rubrum, MRSA e EHEC, 0.2-0.5, 4-9, 250 and 31.25 μg mL-1, respectively.

Silver tungstate as antibacterial coating on titanium surface

Silver tungstate as antibacterial coating on titanium surface

Rare earth doped silver tungstate for photoluminescent applications

Luminescent materials of different emission colors are of great interest for development of new or more efficient optical devices. Although many materials have been reported using different approach, green synthesis and nanosized rare earth doped phosphors of high color rendering is still very limited. This paper describes the structural and luminescence properties of different rare earth doped α-Ag2WO4. The nanophosphors α- (Ag1.97RE0.01)WO4 (RE = Pr, Sm, Eu, Tb, Dy and Tm) were prepared using a simple, fast and cheap coprecipitation methodology. The results revealed that the samples have single phase with orthorhombic symmetry of Pn2n space group. X-ray Photoelectron Spectroscopy (XPS) properties of these phosphors are characterized for the first time. The phosphors show their characteristic emission colors under ultraviolet excitation due to the efficient energy transfer from WO42− group to rare earth ions. Also, the α-(Ag1.97RE0.01)WO4 system offers the possibility of color tuning by changing only the RE3+ dopant instead of altering the host. The photoluminescence properties show the suitability of these inorganic phosphors for solid-state lighting optical devices and for biological applications due to the low toxicity of silver compounds.

Silver Tungstate Nanoparticles for the Detection of Ethanol, Ammonia and Acetone Gases

The design and fabrication of low-cost and fast-response α-Ag2WO4 nanoparticle sensors for the detection of gases like ethanol, ammonia and acetone are reported. Silver tungstate nanocrystals were prepared by a chemical precipitation method, and were characterized by x-ray diffraction, transmission electron microscopy and conductometric methods. The gas-sensing characteristics of α-Ag2WO4 nanoparticles fabricated in the form of thin wafers without any sensitizer coating are reported. The sensor responses of α-Ag2WO4 nanoparticles for ethanol, ammonia and acetone gases were measured as a function of temperature. All the gases showed excellent and fast sensor responses, good repeatability and short recovery times for α-Ag2WO4 nanoparticles.

Promising effects of silver tungstate microcrystals on fibroblast human cells and three dimensional collagen matrix models: A novel non-cytotoxic material to fight oral disease

Silver tungstate (α-Ag2WO4) microcrystals have shown encouraging results regarding their antimicrobial activity. However, in addition to the promising outcomes in fighting oral disease, cytotoxic tests are mandatory for screening new materials for biological applications. Here, we developed a better understanding of the effects of microcrystals on the behavior of both human gingival fibroblast (HGF) cells and three-dimensional (3D) collagen matrices. To perform these experiments, the lowest concentration of α-Ag2WO4 capable of preventing the visible growth of Candida albicans (C. albicans) planktonic cells was defined as the test concentration, and it ranged from 0.781 (C1) to 7.81 (C2) to 78.1 (C3) μg/mL. Complete medium and lysis buffer (LB) served as negative (C-) and positive (C+) controls, respectively. The effect of the microcrystal concentration on the morphology, remodeling and proliferation of HGF cells was evaluated by different approaches. Quantitative and qualitative assessments demonstrated that α-Ag2WO4 did not affect the mitochondrial enzymatic activity of HGF cells cultured in a monolayer or the cell viability within 3D collagen matrices. These experiments showed that α-Ag2WO4 at the C2 concentration did not damage the genomic DNA. The development of new materials is attractive for the possible treatment of diseases and for avoiding indiscriminate prescribing of antibiotics. These findings provide information on the effect of α-Ag2WO4 on cell behavior and reveal that these microcrystals are non-cytotoxic against human gingival cells over a sufficient period to measure the hazard potential.

Effect of Ag2WO4 on the electrical and optical properties of AgI-AgPO3 glasses and fibers for electrophysiology applications

Glasses and fibers belonging to the AgI−AgPO3−Ag2WO4 system are investigated for their combined optical transmission in the visible region and AC electrical conductivity. These glasses combine characteristics that are essentials for a direct application in the fields of optogenetic and electrophysiology. The addition of silver tungstate (Ag2WO4) into the pseudo binary silver iodide phosphate glasses (AgI−AgPO3) allows to increase the durability of the materials against hydrolysis while maintaining an optical transparency in the visible range (450 to 900nm). AC electrical conductivity ranging from 10−3 up to 10−2S·cm−1 at 1MHz frequency was measured on the bulk glasses at room temperature. Moreover, the progressive addition of silver tungstate from 0 to 20mol% results in a linear increase of the glass transition temperature from 106 to 219°C. Electric conductor and light guiding glass fibers of 175μm core diameter were then successfully fabricated by glass preform drawing. Their electrical conductivity at room temperature was measured to be around 0.26S·cm−1 at an AC frequency of 1MHz. These fibers also show optical losses around 5dB·m−1 between 400 and 500nm, making them suitable for the transmission in the blue spectral region used in optogenetic/electrophysiology. This new AgI−AgPO3−Ag2WO4 vitreous system offers glass compositions that are more appropriate in terms of optical transmission to produce multifunctional fibers for electrophysiology experiments than AgI−AgPO3−WO3 glasses previously reported.

Z-type electronic structure and enhanced photocatalytic performance of silver tungstate – phosphorus and aluminum co-doped zinc oxide heterogeneous catalysts

The Z-type electronic structure visible-light-driven silver tungstate–phosphorus and aluminum co-doped zinc oxide (Ag2WO4−PAZO) heterogeneous catalyst was synthesised by a facile hydrothermal method, wherein the proposed Z-type photocatalytic mechanism was supported by the characterisation of X-ray photoelectron spectroscopy, UV–vis diffuse reflection spectroscopy, reactive species, etc. The photocatalytical capacity was demonstrated by degrading the tetracycline hydrochloride (TC-HCl) antibiotics, and it was necessary to eliminate serious pollution caused by the abuse of TC-HCl. In addition, the heterogeneous catalyst showed higher photoactivity than single PAZO or Ag2WO4 catalyst, which was due to its lower photoexcited electron-hole separation. Multiple measurements were applied to characterise the morphology and optical property of the heterogeneous catalyst. The Ag2WO4−PAZO heterogeneous materials also showed more stability compared with Ag2WO4 material.

Low temperature micro Raman and laser induced upconversion and downconversion spectra of europium doped silver tungstate Ag2\u22123xEuxWO4 nanorods

All the red emitting europium-doped silver tungstate α-Ag2−3xEuxWO4 (x = 0.01–0.08 mol) phosphor reported herein crystalise as nanorods. The nanorods were structurally characterised by X-ray powder diffraction, Rietveld refinement, low temperature (20 to −190 °C) micro-Raman spectroscopy . The morphology of the nanorods reported herein was confirmed by field emission scanning electron microscopy. The optical properties were studied using low temperature (20 to −190 °C) high resolution laser excited upconversion and downconversion luminescence.

Synthesis and characterization of a Ce3+ trivalent scheelite-type double tungstate by solid state method

The trivalent cerium silver tungstate, AgCe(WO4)2, with scheelite-like structure has been synthesized by solid-state method despite the relatively high instability of the trivalent Ce ion. This behavior could be explained by the redox properties of Ag2O in the solid state reaction at high temperature in air, which stabilizes the trivalent valence state. X-ray diffraction analysis was carried out and the refinement was performed in the tetragonal S.G. I 41/a (No. 88). Initially differential thermal analysis (DTA) and thermal gravimetric (TG) were used to analyze the reaction process and chemical mechanism. High temperature X-ray diffraction was introduced in to investigate the thermal stability and phase transition properties. It is found that AgCe(WO4)2 can be decomposed into Ag2W2O7 and Ce2(WO4)3 at temperature range of 500 °C – 700 °C. No phase transition was observed up to 900 °C from room temperature. The results of magnetic susceptibility measurement give confirmed evidence that the trivalent cerium cation existed in the compounds Ag(1+x) Ce(1-x)(WO4)2 (x from 0 to 1/3), and no transition from trivalent Ce3+ cation to tetravalent Ce4+ cation was observed even with decreasing cerium concentration. The fluorescence properties of Eu3+ and Tb3+ doped AgCe(WO4)2 were investigated. It is found that Tb3+ is qualified as a local structure probe rather than Eu3+ in the AgCe(WO4)2 compound considering the quenching mechanism which probably due to the metal to metal charge transfer between Ce3+/W6+.

Fabrication and photocatalytic activity enhanced mechanism of direct Z-scheme g-C3N4/Ag2WO4 photocatalyst

Herein, a direct Z-scheme graphitic carbon nitride (g-C3N4)/silver tungstate (Ag2WO4) photocatalyst was prepared by a facile in situ precipitation method using g-C3N4 as a support and silver nitrate as a precursor. X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental mapping demonstrated that β-Ag2WO4 nanoparticles were evenly distributed on the surface of g-C3N4 nanosheets, which acted as a support for the nucleation and growth of β-Ag2WO4 and inhibited the phase transformation of metastable β-Ag2WO4 to stable α-Ag2WO4. Photocatalytic experiments indicated that the g-C3N4/Ag2WO4 nanocomposite photocatalyst displayed a better photocatalytic activity than pure g-C3N4 and Ag2WO4 toward the degradation of methyl orange. The enhanced photocatalytic performance of g-C3N4/Ag2WO4 could be well explained by a direct Z-scheme photocatalytic mechanism. This mechanism was related to the efficient space separation of photogenerated electron–hole pairs and the great oxidation and reduction capabilities of the g-C3N4/Ag2WO4 system. This work provided new insights into the design and fabrication of g-C3N4-based direct Z-scheme photocatalysts.

Influence of electron beam irradiation on structural and optical properties of α-Ag2WO4 nanoparticles

The influence of 8MeV electron beam irradiation on the structural and optical properties of silver tungstate (α-Ag2WO4) nanoparticles synthesized by chemical precipitation method was investigated. The dose dependent effect of electron irradiation was investigated by various characterization techniques such as, X-ray diffraction, scanning electron microscopy, UV–vis absorption spectroscopy, photoluminescence and Raman spectroscopy. Systematic studies confirm that electron beam irradiation induces non-stoichiometry, defects and particle size variation on α-Ag2WO4, which in turn results changes in optical band gap, photoluminescence spectra and Raman bands.

Cytotoxic effects of silver tungstate microcrystals on fibroblast human cells

Cytotoxic effects of silver tungstate microcrystals on fibroblast human cells

Synthesis and characterization of metastable β-Ag2WO4: an experimental and theoretical approach.

Metastable silver tungstate (β-Ag2WO4) has attracted much attention lately because of its many potential applications. However, the synthesis of metastable phases of inorganic compounds is challenging because of the ease of transformation to the stable phase. We have overcome this challenge and have successfully synthesized β-Ag2WO4 microcrystals using a dropwise precipitation (DP) method in aqueous media at low temperature. The microcrystals were characterized by X-ray diffraction (XRD), including powder X-ray diffraction structural determination, field-emission scanning electron microscopy (FE-SEM), and micro-Raman/ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. To complement the experimental data, we present first-principles quantum-mechanical density functional theory (DFT) calculations. Using XRD data, Raman/UV-vis data, and the determined optical band gap, together with geometric optimization calculations, we confirmed the structure of this compound. β-Ag2WO4 has a hexagonal structure with a P63/m space group. The building blocks of the lattice comprise two types of W-O clusters, [WO4] and [WO5], coordinated to four and five O atoms, respectively, and two types of Ag-O clusters, [AgO6], and [AgO5], linked to six and five O atoms, respectively. This type of fundamental study, combining multiple experimental methods and first-principles calculations, helps to obtain a basic understanding of the local structure and bonding in the material.