Room temperature gas sensor based on rGO/Bi₂S₃ heterostructures for ultrasensitive and rapid NO₂ detection

Bismuth sulfide (Bi₂S₃) is a promising material for detecting NO₂ molecules at room temperature thanks to its narrow and tunable bandgap. However, pure Bi₂S₃ suffers from some sensing blemish because of its low electroconductivity and poor charge transfer efficiency. Herein, we synthesized the high sensing response room temperature NO₂ detection materials composed of Bi₂S₃ nanoflowers and reduced graphene oxide (rGO). The formed conductive network and heterojunctions between Bi₂S₃ nanoflowers and rGO nanosheets dramatically improve the conductivity and electron transfer efficiency. The excellent rGO/Bi₂S₃ sensor shows a high sensing response of 9.8 (approximately two times higher than that of the pure Bi₂S₃) and rapid response speed of 22 s (almost half of the pure Bi₂S₃) upon exposure to 1 ppm NO₂ at room temperature. Meanwhile, the rGO/Bi₂S₃ sensor displays superb humidity-independent, selectivity, and stability. These improved NO₂ sensing behaviors can be attributed to the heterointerfaces and the hybrid effects, which accelerate charge transfer efficiency between NO₂ molecules and the surface of rGO/Bi₂S₃ heterostructure. To enable on-line detection of ambient hazardous gas, we designed a portable wireless NO₂ detector based on rGO/Bi₂S₃ heterostructure. This study offer an insightful guidance for improving the NO₂ sensing behaviors of metal chalcogenides.