Ag-Modified SnS2/SnO2 Nanoheterojunctions for Low-Temperature NO2 Sensing

Realizing low-temperature detection of NO2 is crucial to protecting the environment and human health. In this study, SnS2/SnO2 hexagonal nanosheets with an average size of 630 nm were synthesized by a two-step process. Subsequently, Ag nanoparticles were modified on the surface of SnS2/SnO2 to form Ag-modified SnS2/SnO2 nanoheterojunctions. Compared to SnS2 and SnS2/SnO2 sensors, Ag/SnS2/SnO2-based sensors have better gas-sensing performance at the optimum operating temperature of 100 °C, including higher response, better stability, and excellent selectivity to NO2. The response value of the Ag/SnS2/SnO2 sensor to 7 ppm of NO2 at 100 °C is 56.4, which is four times higher than that of the SnS2 sensor. The outstanding NO2 sensing properties of the Ag/SnS2/SnO2 can be due to the combination of Ag modification and the formation of the SnS2–SnO2 heterojunction.