Ultrasensitive and selective CuO/GaN co-decorated SnO2 nanowire gas sensor with ppb-level detection of H2S gas

H₂S gas, which has a highly unpleasant odor, is highly toxic, flammable, and corrosive; hence, development of reliable, highly selective ppb-level sensitive H₂S gas sensors is vital. Herein, we obtained SnO₂ nanowires (NWs) through a vapor–liquid–solid mechanism and GaN nanoparticles (NPs) were decorated on them. Subsequently, CuO NPs were decorated on the GaN-decorated SnO₂ NWs. Various characterization methods confirmed the formation of crystalline materials with NW morphology and the uniform dispersion of CuO and GaN NPs on SnO₂ NWs with the desired chemical composition. A bare SnO₂ NW gas sensor yielded a low response of 1.35 to 10 ppm H₂S at 300°C, whereas after GaN and CuO/GaN co-decoration on SnO₂ NWs, the responses increased to 37 and 7268, respectively. Furthermore, the optimal gas sensor yielded excellent repeatability, selectivity, and long-term stability. The enhanced output was stemmed from the transformation of CuO to CuS with high metallic conductance, the interface junctions formed between GaN and SnO₂, and CuO and SnO₂, which affect charge transport, and the availability of numerous abundant reaction sites attributed to the nanowire-based structural configuration.