Ag-Modified SnS<sub>2</sub>/SnO<sub>2</sub> Nanoheterojunctions\nfor Low-Temperature NO<sub>2</sub> Sensing

Realizing low-temperature detection of NO<sub>2</sub> is crucial\nto protecting the environment and human health. In this study, SnS<sub>2</sub>/SnO<sub>2</sub> hexagonal nanosheets with an average size\nof 630 nm were synthesized by a two-step process. Subsequently, Ag\nnanoparticles were modified on the surface of SnS<sub>2</sub>/SnO<sub>2</sub> to form Ag-modified SnS<sub>2</sub>/SnO<sub>2</sub> nanoheterojunctions.\nCompared to SnS<sub>2</sub> and SnS<sub>2</sub>/SnO<sub>2</sub> sensors,\nAg/SnS<sub>2</sub>/SnO<sub>2</sub>-based sensors have better gas-sensing\nperformance at the optimum operating temperature of 100 °C, including\nhigher response, better stability, and excellent selectivity to NO<sub>2</sub>. The response value of the Ag/SnS<sub>2</sub>/SnO<sub>2</sub> sensor to 7 ppm of NO<sub>2</sub> at 100 °C is 56.4, which\nis four times higher than that of the SnS<sub>2</sub> sensor. The\noutstanding NO<sub>2</sub> sensing properties of the Ag/SnS<sub>2</sub>/SnO<sub>2</sub> can be due to the combination of Ag modification\nand the formation of the SnS<sub>2</sub>–SnO<sub>2</sub> heterojunction.