Characterization of h-WO3 nanorods synthesized by hydrothermal process

Fabrication of Tungsten Oxide Nanowalls through HFCVD for Improved Electrochemical Detection of Methylamine

In this study, well-defined tungsten oxide (WO3) nanowall (NW) thin films were synthesized via a controlled hot filament chemical vapor deposition (HFCVD) technique and applied for electrochemical detection of methylamine toxic substances. Herein, for the thin-film growth by HFCVD, the temperature of tungsten (W) wire was held constant at ~1450 °C and gasification was performed by heating of W wire using varied substrate temperatures ranging from 350 °C to 450 °C. At an optimized growth temperature of 400 °C, well-defined and extremely dense WO3 nanowall-like structures were developed on a Si substrate. Structural, crystallographic, and compositional characterizations confirmed that the deposited WO3 thin films possessed monoclinic crystal structures of high crystal quality. For electrochemical sensing applications, WO3 NW thin film was used as an electrode, and cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were measured with a wide concentration range of 20 μM~1 mM of methylamine. The fabricated electrochemical sensor achieved a sensitivity of ~183.65 μA mM-1 cm-2, a limit of detection (LOD) of ~20 μM and a quick response time of 10 s. Thus, the fabricated electrochemical sensor exhibited promising detection of methylamine with considerable stability and reproducibility.

Growth of crystalline WO3-ZnSe nanocomposites: an approach to optical, electrochemical, and catalytic properties

In this study, novel growth of WO₃-ZnSe nanocomposites was carried out by a simple, low-cost hydrothermal process under subcritical conditions and is reported for the first time in just 5 h. The products were characterized in detail by multiform techniques: X-ray diffraction, scanning electron microscopy (SEM), optical studies, and Fourier transform analysis. The influence of ZnSe on the structural, morphological, compositional, optical, and catalytic properties of WO₃ is demonstrated. The WO₃ metal oxide material is grown in a hexagonal crystal structure with wide-band-gap and has been modified by ZnSe to form a composite nanostructures in the nanoscale range. The electrochemical properties of the prepared materials were studied by cyclic voltammetry, which revealed that the synthesized material exhibited remarkable electrochemical supercapacitive activity. Moreover, the composite nanostructures showed excellent photocatalytic activity for degradation of phenol and almost 93% of phenol was degraded with good recyclability and stability. According to The International Commission on Illumination (CIE), the synthesized nanomaterial shows blue emission and is suitable for blue LEDs.

Fabrication of zirconium-based metal-organic frameworks@tungsten trioxide (UiO-66-NH2@WO3) heterostructure on carbon cloth for efficient photocatalytic removal of tetracycline antibiotic under visible light

Designing recyclable photocatalysts with high activity and stability has drawn considerable attention in the fields of sewage treatment. Herein, a series of heterojunctions constructed by zirconium-based metal-organic frameworks (UiO-66-NH₂) and tungsten trioxide (WO₃) is immobilized on carbon cloth via a facile solvothermal method, resulting in highly recyclable photocatalysts. Multiple characterization techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy, verify the successful synthesis of UiO-66-NH₂ nanospheres on the surface of needlelike WO₃ modified carbon cloth. Results show that the optimal heterojunction photocatalyst exhibits excellent photocatalytic degradation efficiency for the removal of tetracycline (TC) from water, for which nearly 100% of TC is degraded within 60 min under visible light. Trapping experiments and electron spin resonance (ESR) spectra analyses demonstrate that the superoxide radicals O₂^- and photogenerated hole h⁺ play a dominant role in the degradation process. Excellent photocatalytic activity is dominantly attributed to the effective separation of photoinduced carriers in this type-Ⅱ heterostructure system. Moreover, the possible photocatalytic oxidation degradation pathway is confirmed by analyzing intermediates using liquid chromatography mass spectrometry (LC-MS). This study offers a highly efficient strategy to design recyclable heterojunction photocatalysts for the degradation of refractory antibiotics in sewage.

Strain engineered biocompatible h-WO3 nanofibers based highly selective and sensitive chemiresistive platform for detection of Catechol in blood sample

In this work, we demonstrate a simple, low-cost biocompatible 1D-WO₃ electrospun nanofibers based strain-induced high-performance chemiresistive catechol sensor. WO₃ nanofibers were synthesized using e-spinning, annealed and drop-casted on to flexible PET substrate. X-Ray Diffraction (XRD) studies confirm the formation of Hexagonal phase-WO₃ and Raman spectroscopy proved the presence of O-W-O bending modes. Field emission scanning electron microscopy (FESEM) images displayed the random orientation of dense WO₃ nanofibers on PET substrate. Hall measurements confirmed the formation of n-type WO₃ nanofibers with carrier density of 10¹⁹ cm^-3. The sensor responded to a broad dynamic range of catechol concentrations from 1 μM to 100 μM with sensitivity of 51.29 μM^-1 cm^-2 and limit of detection of 0.52 μM which are better than previously reported catechol sensors. Interestingly, upon application of compressive strain to the flexible sensor, a remarkable increase in sensitivity to 88.34 μM^-1 cm^-2 was observed with further reduction of the limit of detection to 42 nM. Upon subjecting the sensor to strain ranging from 3.14% to 47.6%, an increase in sensitivity to catechol was observed due to the increase in the exposed surface area of interconnected WO₃ nanofibers which enhances the active sites for catechol oxidation by enhancing the tunneling current. The sensor could detect catechol in simulated blood samples with excellent selectivity against AA, UA, Na⁺, Ca⁺, hydroquinone and glucose.

Effects of sputtering deposited homoseed layer microstructures on crystal growth behavior and photoactivity of chemical route-derived WO3 nanorods

The crystal growth properties of hydrothermally derived WO₃ nanorods were investigated using various WO₃ thin-film seed layers.

Rheological properties and formation mechanism of DC electric fields induced konjac glucomannan-tungsten gels

Konjac glucomannan-tungsten (KGM-T) hydrogel of electrochemical reversibility was successfully produced under DC electric fields in the presence of sodium tungstate. The structure and the effects of sodium tungstate concentration, KGM concentration, voltage and electric processing time on the rheological properties of the gels were investigated. pH experiments showed that KGM sol containing Na2WO4·2H2O in the vicinity of the positive electrode became acidic and the negative electrode basic after the application of DC electric fields. Under acid conditions, WO4(2-) ions transformed into isopoly-tungstic acid ions. FTIR and Raman studies indicated that isopoly-tungstic acid ions absorbed on KGM molecular chain and cross-linked with -OH groups at C-6 position on sugar units of KGM. Frequency sweep data showed with increasing sodium tungstate concentration, voltage, and electric processing time, the viscoelastic moduli, i.e., the storage and the loss moduli of the gel increased, whereas an increase in KGM concentration led to a decrease in gel viscoelastic moduli. The temperature sweep measurements indicated the obtained gel exhibited high thermal stability. Finally, the mechanism of gel formation was proposed. Our work may pave the way to use DC electric fields for the design and development of KGM gels as well as polysaccharide gels.

Tungsten trioxide as a visible light photocatalyst for volatile organic carbon removal

Tungsten trioxide (WO₃) has been demonstrated to possess visible light photoactivity and presents a means of overcoming the UV-light dependence of photocatalysts, such as titanium dioxide. In this study, WO₃ nanostructures have been synthesised by a hydrothermal method using sodium tungstate (Na₂WO₄·2H₂O), sulphate precursors and pH as structure-directing agents and parameters, respectively. By altering the concentration of the sulphate precursors and pH, it was shown that different morphologies and phases of WO₃ can be achieved. The effect of the morphology of the final WO₃ product on the visible light photoactivity of ethylene degradation in the gas phase was investigated. In addition, platinum (Pt) was photodeposited on the WO₃ structures with various morphologies to enhance the photocatalytic properties. It was found that the photocatalytic properties of the WO₃ samples greatly depend on their morphology, chemical composition and surface modification. WO₃ with a cuboid morphology exhibited the highest visible light photoactivity compared to other morphologies, while adding Pt to the surface improved the performance of certain WO₃ structures.