Ultrasensitive and selective rGO QDs modified flower-like Bi₂S₃/Bi₂O₃ heterostructures for room-temperature trace NO₂ detection

Nitrogen dioxide (NO₂) is a ubiquitous ambient pollutant, and chronic exposure to NO₂, even at relatively low concentrations, has been associated with sustained adverse effects on multiple organ systems. Bismuth sulfide offers a promising platform for room-temperature gas sensing, yet its practical use is curtailed by poor charge-transfer efficiency and sparse interfacial active sites. In this study, reduced graphene oxide quantum dots (rGO QDs) modified Bi₂S₃/Bi₂O₃ composites with abundant p-n heterojunctions were fabricated and used for NO₂ detection. The effects of annealing temperature and the amount of rGO on sensor performance were investigated, revealing optimal results for 0.5 wt% rGO modified Bi₂S₃ annealed at 150℃ (rGO_0.5-Bi₂S₃/Bi₂O₃-2). The rGO_0.5-Bi₂S₃/Bi₂O₃-2 sensor exhibited a high response of 36.95 toward 500 ppb NO₂ at room temperature (RT). Experimental results demonstrated theoretical and experimental detection limits (LODs) of 0.6 ppb and 50 ppb for NO₂ respectively, as well as excellent selectivity, anti-interference ability, good repeatability, and long-term stability. By combining band structure alignments analysis with density functional theory (DFT) calculations, the mechanism underlying the enhanced NO₂ detection performance was elucidated, revealing a synergistic effect of the heterojunction interface modulation between components and rGO-promoted charge transfer.