Surface area and surface active sites are two important key parameters in enhancing the gas sensing as well as photocatalytic properties of the parent material. With this motivation, herein, we report a facile synthesis of Reduced Graphene Oxide/Tungsten Oxide RGO/WO₃ hierarchical nanostructures via simple hydrothermal route, and their validation in accomplishment of improved H₂S sensing and highly efficient solar driven photo-degradation of RhB Dye. The self-made RGO using modified Hummer’s method, is utilized to develop the RGO/WO₃ nanocomposites with 0.15, 0.3 and 0.5 wt% of RGO in WO₃ matrix. As-developed nanocomposites were analyzed using various physicochemical techniques such as XRD, FE-SEM, TEM/HRTEM, and EDAX. The creation of hierarchic marigold frameworks culminated in a well affiliated mesoporous system, offering efficient gas delivery networks, leading to a significant increase in sensing response to H₂S. The optimized sensor (RGO/WO₃ with 0.3 wt% loading) exhibited selective response towards H₂S, which is ~ 13 times higher (R_a/R_g = 22.9) than pristine WO₃ (R_a/R_g = 1.78) sensor. Looking at bi-directional application, graphene platform boosted the photocatalytic activity (94% degradation of Rhodamine B dye in 210 min) under natural sunlight. The RGO’s role in increasing the active surface and surface area is clarified by the H₂S gas response analysis and solar-driven photo-degradation of RhB dye solution. The outcome of this study provides the new insights to RGO/WO₃ based nanocomposites’ research spreadsheet, in view of multidisciplinary applications.

A robust synthesis approach to develop CuO/ZnO nanocomposites using microwave-epoxide-assisted hydrothermal synthesis and their proficiency toward H₂S gas-sensing application are reported. The low-cost metal salts (Cu and Zn) as precursors in aqueous media and epoxide (propylene oxide) as a proton scavenger/gelation agent are used for the formation of mixed metal hydroxides. The obtained sol was treated using the microwave hydrothermal process to yield the high-surface area (34.71 m²/g) CuO/ZnO nanocomposite. The developed nanocomposites (1.25–10 mol % Cu doping) showcase hexagonal ZnO and monoclinic CuO structures, with an average crystallite size in the range of 18–29 nm wrt Cu doping in the ZnO matrix. The optimized nanocomposite (2.5 mol % Cu doping) showed a lowest crystallite size of 21.64 nm, which reduced further to 18.06 nm upon graphene oxide addition. Morphological analyses (scanning electron microscopy and transmission electron microscopy) exhibited rounded grains along with copious channels typical for sol–gel-based materials . Elemental mapping displayed the good dispersion of Cu in the ZnO matrix. When these materials are employed as a gas sensor, they demonstrated high sensitivity and selectivity toward H₂S gas in comparison with the reducing gases and volatile organic compounds under investigation. The systematic doping of Cu in the ZnO matrix exhibited an improved response from 76.66 to 94.28%, with reduction in operating temperature from 300 to 250 °C. The 2.5 mol % doped Cu in ZnO was found to impart a response of 23 s for 25 ppm of H₂S. Gas-sensing properties are described using an interplay of epoxide-assisted sol–gel chemistry and structural and morphological properties of the developed material.

Interest in the importance of gas sensing devices has increased significantly due to their critical function in monitoring the environment and controlling pollution, resulting in an increased market demand. The present review explores perovskite La-Fe-O based gas sensors with a special focus on LaFeO3 and evaluates their sensitivity to a diverse range of practical target gases that need to be monitored. An analysis has been conducted to assess different routes not only of synthesizing LaFeO3 material but also of characterization with the targeted use for their gas sensing abilities. Additionally, a comprehensive analysis has been performed to explore the effect of introducing other elements through doping. In view of the LaFeO3 sensing performance, more common gases like acetone, ethanol, methanol, formaldehyde, NOx, and CO2 have been targeted. In addition, a discussion on uncommon gases such as CO, SO2, TEA, C2H5, C6H6, and others is also made to give a complete picture of LaFeO3-based gas sensors. The summary and conclusion section of the study addresses the primary obstacles in the synthesis process, the variables that restrict the sensing capabilities of LaFeO3, and its commercial fulfillment.

We report a facile, green synthesis of graphene/Ag/ZnO nanocomposites and their use as acetone sensors via a medicinal plant extraction assisted precipitation process. The choice of plant extract in combination with metal nitrates led to self-sustaining colloid chemistry. Along with the green synthesis strategy, structural, morphological and gas sensing properties are described.