Search Results (4)

Benzene, as a typical toxic gas and carcinogen, is an important detection object in the field of environmental monitoring. However, it remains challenging for the conventional resistance-type gas sensor to effectively detect low-concentration (ppb-level) benzene gas molecules, owing to their insufficient reaction activation energy, especially when operating at room temperature. Herein, a field-effect transistor (FET)-type gas sensor using carbon nanotubes as a channel material is proposed for the efficient detection of trace benzene, where carbon nanotubes (CNTs) with high semiconductor purity act as the main channel material, and ZnO/WS₂ nanocomposites serve as the gate sensitive material. On the basis of the remarkable amplification effect in CNTs-based FET, the proposed gas sensor manifests desirable sensitive ability with the detection limit as low as 500 ppb for benzene even working at room temperature, and the sensor also exhibits fast response speed (90 s), high consistency with a response deviation of less than 5%, and long-term stability of up to 30 days. Furthermore, utilizing Tenax TA as the screening unit, the as-proposed gas sensor can achieve the feasible selective detection of benzene. These experimental results demonstrate that the strategy proposed here can provide significant guidance for the development of high-performance gas sensors to detect trace benzene gas at room temperature. Full article

Robust hybrid g-C₃N₄/ZnO-W/Co_x heterojunction composites were synthesized using graphitic carbon nitride (g-C₃N₄) and ZnO-W nanoparticles (NPs) and different concentrations of Co dopant. The hybrid heterojunction composites were prepared by simple and low-cost coprecipitation methods. The fabricated catalyst was explored and investigated using various characterization techniques such as FTIR, XRD, FESEM and EDX. The surface morphology of the as-prepared hybrid nanocomposites with particle sizes in the range of 15–16 nm was validated by SEM analysis. The elemental composition of the synthesized composites was confirmed by EDS analysis. Photocatalysis using a photon as the sole energy source is considered a challenging approach for organic transformations under ambient conditions. The photocatalytic activity of the heterojunctions was tested by photodegrading methylene blue (MB) dye in the presence of sunlight. The reduced band gap of the heterojunction composite of 3.22–2.28 eV revealed that the incorporation of metal ions played an imperative role in modulating the light absorption range for photocatalytic applications. The as-synthesized g-C₃N₄/ZnO-W/Co_0.010 composite suppressed the charge recombination ability during the photocatalytic degradation of methylene blue (MB) dye. The ternary heterojunction C₃N₄/ZnO-W/Co_0.010 composite showed an impressive photocatalytic performance with 90% degradation of MB under visible light within 90 min of irradiation, compared to the outcomes achieved with the other compositions. Lastly, the synthesized composites showed good recyclability and mechanical stability over five cycles, confirming them as promising photocatalyst options in the future. Full article

Tungsten sulfide decorated with indium oxide nanoparticles (In₂O₃/WS₂) was studied for a chemiresistive-type NH₃ sensor at room temperature. It was found that the responses of the developed In₂O₃/WS₂ heterostructure nanocomposite-based sensors are significantly improved to 3.81 from 1.45 for WS₂. The response and recovery time of the heterostructure-based sensor was found to significantly decrease to 88 s/116 s (10 ppm) from 112 s/192 s for the WS₂-based one. The sensor also exhibits excellent selectivity and signal reproducibility. In comparison to WS₂ decorated with both ZnO and SnO₂ in similar ways, the In₂O₃-decorated WS₂ has overall better sensing performance in terms of sensitivity, selectivity and response/recovery speeds for NH₃ from 1 ppm to 10 ppm at room temperature. The improved sensing properties of WS₂ incorporating In₂O₃ could be attributed to the joint enhancement mechanisms of the “electronic and catalytic” sensitizations. Full article

Transition metal dichalcogenide (TMD) MoS${}_2$ and WS${}_2$ monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS${}_2$@ZnO and WS${}_2$@ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS${}_2$ and WS${}_2$ monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications. Full article