Cerium Tungstate Research Articles

Electrochemical sensing platform using cerium tungstate for highly sensitive sensing of chromium in water

Chromium, in some forms and large amounts, can be hazardous to human health and the environment. In particular, hexavalent chromium Cr(VI) and its derivatives are the most poisonous forms of Cr, whose toxicity depends on its oxidation state. Herein, cerium tungstate (CeW) is demonstrated as an efficient sensing material for Cr(VI) detection in aqueous medium. Two different surfactants are used to hydrothermally synthesize flake-like and sphere-like morphology. The flake-like morphology shows excellent Cr(VI) detection ability owing to its larger surface area, oxygen vacancy defects, and electrochemically active surface area. The sensitivity and limit of detection (LoD) value of the CeW nanoflakes are found to be 0.71 μA/ppb and 6.1 ppb, respectively. The LoD is lower than the WHO recommended standard value, which suggests that the synthesized material can be used for determining Cr(VI) concentration in domestic and potable water. The presence of different ions, such as Fe3+, Zn2+, Cu2+, Hg2+and Pb2+in the medium is found not interfere the Cr(VI) detection ability of CeW nanoflakes and thereby enhancing its practical applicability in Cr(VI) detection.

Construction of novel Ce2(WO4)3/rGO nanocomposites for efficient photocatalytic mitigation of antibiotic drug chloramphenicol

In this study, we present the synthesis and characterization of a novel cerium tungstate decorated reduced graphene oxide (Ce2(WO4)3@rGO or CeW@rGO) nanocomposite via a facile hydrothermal method. Comprehensive analyses including XRD, FTIR, SEM, TEM, and XPS were conducted to elucidate the crystal structure, chemical states, morphology, and optical properties of the synthesized nanocomposite. The CeW@rGO exhibited a reduced band gap of 2.14 eV compared to 2.33 eV for CeW, enhancing visible light absorption. Photocatalytic experiments demonstrated the superior efficiency of CeW@rGO, achieving 98.03 % degradation of the antibiotic chloramphenicol (CIP) within 45 min under visible light irradiation. The enhanced photocatalytic performance is attributed to the improved charge separation and extended lifetime of photo-induced charge carriers, facilitated by the rGO. Reactive oxidative species such as O2•− and •OH were identified as key contributors to the degradation process, as confirmed by radical scavenging studies. The plausible degradation mechanism of CIP was proposed based on LC-MS analysis. This work highlights the potential of CeW@rGO as an efficient and sustainable photocatalyst for environmental remediation, offering significant advancements in the field of photocatalytic degradation of organic contaminants. The improved efficiency of the photocatalyst was primarily due to the enlarged surface area and the addition of CeW and rGO to the composite sample. These additions enhance the catalyst's ability to adsorb pollutants and increase the separation of electrons and holes at the interface between two semiconductors by creating an internal electric field. The results toprovide the successfully creation ofCeW/rGO nanocomposites that are cost-effective, highly efficient, lightweight, and sustainable for use in environmental applications.

Investigation of g-C3N4/Ce2(WO4)3 Nanocomposites for the Removal of Basic Dyes.

Herein, we have synthesized pristine and g-C3N4-assisted Ce2(WO4)3 via a facile hydrothermal method. The structure was confirmed with the standard JCPDS card. g-C3N4 encapsulated the crystal and reduced the size. The Raman spectra revealed the presence of Ce-O, W-O stretching and bending vibrations. Electron hole transfer facilitation and controllable recombination were altered by g-C3N4 heterojunction with cerium tungstate. Ce2(WO4)3 possessed a larger band gap. As g-C3N4 was assisted, the band gap was reduced which facilitates Ce2(WO4)3 to utilize more visible light. The prepared photocatalysts were used to investigate the model pollutant removal with visible light. The pure Janus Green B sample showed lesser efficiency, as it does not show self-degradation under light. As Ce2(WO4)3 was added, it slightly improved the efficiency as it possesses lower electron hole transfer and high recombination. Thus, g-C3N4 was composited with Ce2(WO4)3 to make heterojunctions which will enhance the photo-excited electron and hole transfer and decrease e-/h+ recombination. The rate constant values of the photocatalysts were calculated, and the system follows the first-order pseudo-kinetic model. Ciprofloxacin, a well-known antibiotic, was also used to degrade under visible light. The pure sample showed lower efficiency, and the antibiotic was reduced well with the addition of prepared photocatalysts. The modification of Ce2(WO4)3 with the optimum-level g-C3N4 facilitated electron hole charge transfer, and numerous adsorbed dye molecules on the photocatalyst surface made 0.1 g g-C3N4-Ce2(WO4)3 a plausible photocatalyst for the water remediation process.

Triangle-Shaped Cerium Tungstate Nanoparticles Used to Modify Carbon Paste Electrode for Sensitive Hydroquinone Detection in Water Samples.

In this study, we propose an eco-friendly method for synthesizing cerium tungstate nanoparticles using hydrothermal techniques. We used scanning, transmission electron microscopy, and X-ray diffraction to analyze the morphology of the synthesized nanoparticles. The results showed that the synthesized nanoparticles were uniform and highly crystalline, with a particle size of about 50 nm. The electrocatalytic properties of the nanoparticles were then investigated using cyclic voltammetry and electrochemical impedance spectroscopy. We further used the synthesized nanoparticles to develop an electrochemical sensor based on a carbon paste electrode that can detect hydroquinone. By optimizing the differential pulse voltammetric method, a wide linearity range of 0.4 to 45 µM and a low detection limit of 0.06 µM were obtained. The developed sensor also expressed excellent repeatability (RSD up to 3.8%) and reproducibility (RSD below 5%). Interferences had an insignificant impact on the determination of analytes, making it possible to use this method for monitoring hydroquinone concentrations in tap water. This study introduces a new approach to the chemistry of materials and the environment and demonstrates that a careful selection of components can lead to new horizons in analytical chemistry.

Nanocrystalline cerium tungstate and its dysprosium doped forms with high NIR reflectance

Nanocrystalline cerium tungstate and its 6 % dysprosium doped nanocrystals have been prepared by the chemical precipitation followed by the heat treatment at 600 °C. X-ray diffraction studies confirm the crystalline formation of the cerium tungstate phase without any secondary phases occurring due to dysprosium doping. The doping caused a small variation in the crystallite size. Transmission electron microscopic images show the agglomeration of the particles and the high-resolution transmission electron microscope images exhibit the different planes of the polycrystalline samples. Energy-dispersive X-ray spectroscopic analysis confirms the presence of elements present in the material. The characteristic vibrations due to the W-O-W and O-W-O stretching modes characteristics of tetrahedral tungstates (WO42-) are confirmed from Fourier transform infrared spectra. UV–Vis-NIR reflectance studies show high reflectance in the near-infrared region. Also, the samples show high absorption in the visible and ultraviolet regions.

Exploitation the unique acidity of novel cerium-tungstate catalysts in the preparation of indole derivatives under eco-friendly acid catalyzed Fischer indole reaction protocol

Solid acidic cerium tungstate catalysts containing different molar ratios of cerium and tungstate were prepared by direct solvothermal methodology. The structure of the prepared catalysts was deeply studied and confirmed based on different characterization techniques such as DTA-TGA, FTIR, Raman spectra, XRD and N 2 adsorption measurements. Moreover, FTIR and TPD of chemically adsorbed pyridine techniques were conducted to fully address the nature and the strength of the acidic sites of the prepared catalysts. The study showed that at a lower molar ratio of tungstate, the catalyst contains cerium oxide phase and slight participation of cerium tungstate phase, which gradually increases with further increase of tungstate molar ratio. This phase change was also accompanied by a noticeable change in the thermal stability, surface area and acidic properties of the prepared catalysts. Additionally, the techniques used to study the acidic properties showed an excellent enhancement in the acidic centers. It was also noted that the strength of these acidic centers reached the maximum in the case of using tungstate: cerium molar ratio 2:1 (CeW2.0) catalyst, and slightly decreased thereafter. By exploiting the acidic properties of the prepared catalysts, a series of indole derivatives were synthesized via the Fischer indole synthesis strategy. The results also showed that ∼100% of indole derivatives were obtained using 0.02 g catalyst at 80 °C after 2 h only. Moreover, the Reuse experiment demonstrated the possibility of recycling and reusing the catalyst through many cycles with high efficiency, indicating its wonderful constancy and reusability.

Influence of lanthanum doping on the structural and optical properties of cerium tungstate nanocrystals

In this study, the effect of lanthanum (La) doping on the structural and optical properties of cerium tungstate nanocrystals synthesized by the chemical precipitation method is investigated. The X-ray diffraction studies confirmed the crystalline phase formation and observed no phase change with doping. It is interesting to note that the crystallite size is decreased with La doping. The characteristic vibrational peaks of W-O bonds are confirmed from the FTIR and Raman spectroscopic studies and found no appreciable changes in the spectral positions with doping. The optical properties are studied using UV-Vis spectroscopy and photoluminescence spectroscopy. The characteristic broad blue PL emission from the tetrahedral tungstate group is observed for the pure and doped samples, and the appreciable variation in PL intensity can be associated with the formation of defects that occurred while doping.

Characterization of Ce2(WO4)3 nanocrystals for potential applications

In this work, the chemical precipitation synthesis route is employed for the fabrication of cerium tungstate nanoparticles. The as-synthesized particles are calcined at three different temperatures, and their structural and optical properties are studied. The optical bandgap is found to be decreased with an increase in calcination temperature. Photoluminescence emission spectra of the cerium tungstate samples exhibit a broad blue emission characteristic of the tetrahedral tungstate group. The present work aims to investigate the influence of calcination temperature on the structural and optical properties of cerium tungstate nanoparticles. Results of the characterization offer the suitability of the material in luminescence and optoelectronics applications. The results of the present work constitute the first report for the detailed optical properties of cerium tungstate nanoparticles.

Increased in vitro Anti-HIV Activity of Caffeinium-Functionalized Polyoxometalates.

Polyoxometalates (POMs), molecular metal oxide anions, are inorganic clusters with promising antiviral activity. Herein we report increased anti‐HIV‐1 activity of a POM when electrostatically combined with organic counter‐cations. To this end, Keggin‐type cerium tungstate POMs have been combined with organic methyl‐caffeinium (Caf) cations, and their cytotoxicity, antiviral activity and mode of action have been studied. The novel compound, Caf4K[β2‐CeSiW11O39]×H2O, exhibits sub‐nanomolar antiviral activity and inhibits HIV‐1 infectivity by acting on an early step of the viral infection cycle. This work demonstrates that combination of POM anions and organic bioactive cations can be a powerful new strategy to increase antiviral activity of these inorganic compounds.

Enhanced photoactivity of cerium tungstate-modified graphitic carbon nitride heterojunction photocatalyst for the photodegradation of moxifloxacin

Design and optimization of visible-light-driven photocatalysts for degradation of organic pollutants is an important step towards environmental decontamination. In this study, wolframite cerium tungstate (Ce2(WO4)3, (CW)) hybridized with g-C3N4 (CN) nanosheets was synthesized via a simple hydrothermal route followed by an ultrasound-assisted synthesis method. The prepared Ce2(WO4)3@ g-C3N4 (CW@CN) heterojunction was investigated for photocatalytic degradation of the antibiotic moxifloxacin (MXF) under visible light irradiation. Structural, morphological, and optical properties as well as chemical composition of the as-synthesized heterojunction were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence (PL). MXF photocatalytic degradation by the binary nanostructure (Ce2(WO4)3@ g-C3N4) (94.1%) was the highest compared to g-C3N4 (53.6%) and Ce2(WO4)3 (46.4%). Such enhanced activity could be ascribed to efficient suppression of the charge carriers’ recombination, leading to adequate formation of the reactive species responsible for MXF degradation. Furthermore, the Ce2(WO4)3@ g-C3N4 heterojunction showed remarkable stability over five consecutive cycles, with only 11.5% reduction after the 5th cycle. This work established the potential applicability of Ce2(WO4)3@ g-C3N4 nanostructures towards photocatalytic removal of MXF.

Structural and electrical properties of cerium tungstate: Application to methane conversion

The catalytic efficiency as well as the electrical conduction mechanism of Ce2(WO4)3 powders synthetized for the oxidation of methane were investigated. Total and partial oxidation reactions were observed in the temperature range between 600 and 750 °C under CH4/dry air flux, for low CH4 concentrations. The electrical conduction mechanism is based on electron tunneling at low temperature (<650 °C) and hopping over an ion barrier at high temperature, which favors the catalytic oxidation of CH4 in air; these mechanisms occur during the partial and total oxidation under weak gas flow. The occurrence of these types of conduction mechanism was related both to the distorted monoclinic structure of Ce2(WO4)3 and to the larger structural cavities, as evidenced respectively by X-ray diffraction analyses (Rietveld analyses) and high-resolution transmission electron microscopy. The oxidation state of cerium is 3 + in the compound, as revealed by XPS investigations.

Synthesis and Supercapacitor Application of Cerium Tungstate Nanostructure

AbstractCerium tungstate nanostructure was prepared through precipitation and characterized using field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR), as well as cyclic voltammetry (CV), galvanostatic charge‐discharge, electrochemical impedance spectroscopy (EIS) and continuous cyclic voltammetry (CCV) in terms of structural and electrochemical properties. The electrochemical evaluations using cerium tungstate electrodes revealed that the electrode material has interesting supercapacitive properties including a specific capacitance (SC) of 348 F g−1 at a potential scan rate of 2 mV s−1. Also CCV experiments proved that the material maintains 95.8% of its original capacitance after 4000 cycles. The properties make the nanostructures suitable for use as high‐quality electroactive materials for supercapacitor applications.

Catalytic properties of Sr1−xCexWO4: The role of mixed conduction in methane oxidation

The catalytic efficiency of ternary strontium cerium tungstate Sr0.5Ce0.35WO4, for the production of syngas through methane oxidation, was investigated and compared to those of binary strontium tungstate SrWO4. Total and partial oxidation reactions were observed for both samples in the temperature range 600–750 °C under CH4/dry air flux. At high CH4 concentration and low temperature with the ternary tungstate as catalyst, the partial oxidation, leading to CO/H2, prevails. This indicates the potentiality of the new strontium cerium tungstate scheelite compound for the catalysis of CH4. Sr0.5Ce0.35WO4 and SrWO4 exhibit different conduction mechanisms. Conduction in the binary compound is related to the overlapping large polaron tunneling model, whereas conduction in the ternary one is due to a correlated barrier hopping phenomenon. The activation energies, in the low temperature range where the partial oxidation occurs, are significantly lower for the ternary compound than for the binary one. These electrical tendencies favor both partial and total oxidation of methane. The correlated barrier hopping conduction in the ternary compound leads to a better partial oxidation rate than conduction through large polaron tunneling.

Adsorption and Separation of 152+154Eu(III) and 60Co(II) Using Cerium(IV) Tungstate

Samples of cerium(IV) tungstate (CeW) inorganic ion exchanger were synthesized using different Ce(IV) salts: (NH4)2Ce(NO3)6·2H2O, (NH4)4Ce(SO4)4·2H2O, and Ce(SO4)2·4H2O. The samples were characterized using FT-IR and X-ray diffraction. The adsorption behavior of 152+154Eu(III) and 60Co(II) on CeW was studied under batch and dynamic conditions. Factors influencing the adsorption kinetics were examined. Loading and elution behavior of both ions was studied using different eluents. Complete separation of Eu(III) and Co(II) (152+154Eu and 60Co tracers) was achieved using small columns packed with CeW.

Preparation and characterization of PANI@G/CWO nanocomposite for enhanced 2-nitrophenol sensing

Abstract A new material by polymer insertion via graphene oxide into cerium tungstate was prepared by very simple oxidation-reduction method. Aniline polymerization was done on the surface of graphene oxide (GO) which was reduced to graphene (G) simultaneously mixed with separately prepared inorganic matrices of cerium tungstate (Ce 2 (WO 4 ) 3 (CWO)). PANI@G/CWO was characterized by various spectroscopic methods as SEM, FTIR, TGA, XRD and XPS to confirm its possibilities. Selective 2-nitrophenol sensor was fabricated on flat glassy carbon electrode (GCE) and PANI@G/CWO nanocomposites in the form of thin layer. It was found excellent sensitivity as well as long life spam with broad dynamic concentration range (LDR) that showed efficient electrochemical performance towards 2-nitrophenol on fabricated chemical sensor by PANI@G/CWO. The linear calibration curve (r 2 = 0.9914) with wide range of 2-nitrophenol concentration (1.0 nM–1.0 mM) was found having the detection limit of 0.87 nM while the sensitivity of the sensor was around 1.229 μ A μM −1 cm −2 . It was introduced a new route for the development of a versatile phenolic sensor based on PANI@G/CWO nanocomposites by I–V method that is proved more selective and sensitive for environmental toxic materials.

A Novel Cerium Tungstate Nanosheets Modified Electrode for the Effective Electrochemical Detection of Carcinogenic Nitrite Ions

AbstractIn this present scenario, for the first time, we propose a facile and simple wet chemical approach for the fabrication of two‐dimensional (2D) cerium tungstate (CeW2O9;CeW) nanosheets and evaluated as an electrochemical sensor for the detection of nitrite ions. The successful formation of CeW2O9 nanosheets was confirmed by various physicochemical techniques such as X‐ray diffraction, Fourier transform infrared spectroscopy, Raman, Scanning electron microscope, Transmission electron microscope and Energy dispersive X‐ray studies. The electrochemical properties of the CeW nanosheets were studied by using cyclic voltammograms (CV) and chronoamperometric techniques. As an electrochemical sensor, the CeW nanosheets modified glassy carbon electrode (GCE) showed superior electrocatalytic activity in the oxidation of nitrite in terms of higher anodic peak current and lower oxidation potential when compared with unmodified GCE. CeW nanosheets based electrochemical sensor has been fabricated which detect nitrite in wide linear response range, good sensitivity and very low detection limit of 0.02–986 μM, 2.85 μA μM−1 cm−2 and 8 nM, respectively. Moreover, the CeW nanosheets modified GCE exhibited excellent selectivity even in the presence of common metal ions and biologically co‐interfering compounds. For the practical viability of the prepared amperometric sensor has been utilized in various water samples such as tap, lake and drinking water and the obtained recoveries are appreciable.

Toward Facile Preparation and Design of Mulberry-Shaped Poly(2-methylaniline)-Ce2(WO4)3@CNT Nanocomposite and Its Application for Electrochemical Cd2+ Ion Detection for Environment Remediation

ABSTRACTNovel hybrid material was prepared by adding slurries of poly(N-methylaniline) and cerium tungstate [Ce2(WO4)3] into a conical flask contained dispersed carbon nanotubes. It was characterized by scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Electrical conductivity of poly(N-methylaniline)-Ce2(WO4)3@carbon nanotube samples was determined using four-probe method. The thin layer of poly(N-methylaniline)-Ce2(WO4)3@carbon nanotube was fabricated onto glassy carbon electrode for a selective Cd2+ ion sensor. The calibration plot is linear (r2 = 0.9917) over the large Cd2+ concentration ranges (1.0 nM–1.0 mM). The sensitivity, detection limit is ∼5.138 µA µM−1 cm−2 and ∼0.11 nM (signal-to-noise ratio, at a SNR of 3), respectively.

Growth of transition metals on cerium tungstate model catalyst layers

Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

Growth of cerium tungstate epitaxial layers: influence of temperature

Thin films of cerium tungstate prepared in situ by cerium deposition in oxygen atmosphere onto the W(100) single‐crystal were investigated by means of photoelectron spectroscopy and low‐energy electron diffraction (LEED). The studied temperature range was 173–1073 K. It was found that the temperature necessary for the oriented growth of Ce6WO12(100) was 673 K, and at higher temperatures, the LEED pattern improved. Photoemission data revealed the partial formation of CeO2 on the surface at preparation temperatures below 473 K due to limited diffusion of tungsten atoms from the substrate. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Hydrothermal stability of MOx-Ce0.75Zr0.25O2 catalysts for NOx reduction by ammonia

Various acidic components (MOx: phosphate, sulfate, tungstate and niobate) were loaded on Ce0.75Zr0.25O2 powders by an impregnation method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol.% H2O to obtain the aged catalysts. The catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2 programmed-reduction, NH3 adsorption and deNOx activity measurements. The results showed that, among the catalysts investigated, the phosphated Ce0.75Zr0.25O2 catalyst showed the highest hydrothermal stability. The remained high acidity of the phosphated catalyst with moderate redox property helped to maintain the excellent NH3-SCR activity of hydrothermally aged catalyst. Cerium tungstate led to the poor redox property of the tungstated catalyst although the acidity of catalyst was still high. The decomposition of sulfates at temperatures higher than 600 °C restrained the usage of sulfated catalysts in high temperature conditions. The overall dehydration of niobate to niobium oxides led to the low acidity of hydrothermally aged Nb2O5-Ce0.75Zr0.25O2 catalyst.