Ultrasensitive low-temperature H₂S detection enabled by microwave-synthesized CuO/SnO₂/RGO composite nanosheets with abundant heterojunctions

Hydrogen sulfide (H₂S) poses a significant threat to human health even at trace levels. Rapid and reliable H₂S detection with high sensitivity is of paramount importance. Herein, copper oxide and tin dioxide co-modified reduced graphene oxide (CuO/SnO₂/RGO) composite nanosheets (CSR) were synthesized via a one-step microwave-assisted method and used as functional sensing layers for H₂S detection. The composite consists of secondary CuO and SnO₂ nanoparticles, in-situ grown and uniformly anchored onto the RGO surfaces. The 3-CSR composite with a Cu: Sn molar ratio of 3: 7 has a particle size range from 6.3 to 25.1 nm with an average diameter of 11.8 nm. The formation mechanism stems from the initial coordination of Sn²⁺ and Cu²⁺ ions with the oxygen-containing functional groups on the GO surface. The CSR sensor demonstrates an exceptional sensing response to H₂S, which is significantly modulated by the Cu/Sn molar ratio. The optimized 3-CSR composite exhibits superior gas-sensing properties, achieving a remarkable response of 28233 toward 50 ppm H₂S with an ultra-fast response time of merely 2 s at a low operating temperature of 80 °C. The enhanced performance is attributed to the synergistic effects of numerous p-n heterojunctions, together with the highly RGO network, high specific surface area, and oxygen vacancy defect, which promotes gas adsorption and charge transfer.