Flexible, 3D SnS₂/Reduced graphene oxide heterostructured NO₂ sensor

Graphene (Gr) has been recognized as a promising candidate for room temperature (RT), high-performance gas sensing due to its unique structure and electronic properties. However, the poor selectivity of pristine Gr hinders its practical application in NO₂ detection. SnS₂ displays a strong physical affinity to NO₂, while the ultrahigh resistance and low sensitivity at RT limit its utility. Here, 3D structured SnS₂/reduced graphene oxide (RGO) heterojunction, a novel gas responsive material merging the merits of RGO and SnS₂, is synthesized through a facile hydrothermal route. The 3D SnS₂/RGO displays impressive NO₂ sensing performance, including high sensitivity (6.1 ppm⁻¹), excellent selectivity, low theoretical limit of detection (8.7 ppb), linearity and reversibility. The SnS₂/RGO heterojunction exhibits 22.6 times higher response to NO₂ than the pristine RGO, indicating the remarkable role of surface decoration in enhancing the gas sensing performance of RGO. The high sensitivity originates from the formation of heterojunction and 3D porous structures, which promote NO₂ adsorption, diffusion and charge transfer by providing alternative adsorption sites and charge transport paths. Notably, a liquid crystal polymer substrate is employed to fabricate a flexible NO₂ sensor with endurance to mechanical deformation. The elevated temperature improves the response and recovery kinetics.