LAUSR

Abstract Sensing of Nitrogen dioxide (NO2) is of great importance for its pernicious and destructive impacts to both human health and nature environment. However, it still remains challenging to achieve the NO2 detection with fast response, high sensitivity and good selectivity. In this work, two-dimensional (2D) ultrathin n-type SnS2 nanosheets with Mo doping have been synthesized via a simple single-step solvothermal method and exploited for NO2 sensing application. Phase and structural analyses confirm the homogeneous cation alloying of Mo (1% ~ 10%) in the SnS2. It is indicated that the Mo doping can elegantly tune the electronic structure of SnS2 and promote the sensing process with negative adsorption energy. Especially for 3%Mo-SnS2 nanosheet, the NO2 sensing response at 150 ℃ has been enhanced around 23 times relative to the un-doped SnS2 sample, together with fast sensing kinetics and good NO2 selectivity. Interestingly, the n-type SnS2-based sensor shows an abnormal response characteristic for the first time with resistance decrease at low NO2 concentration, behaving like a p-type semiconductor. The P-N sensing transition can be regulated by varying the operation temperature and NO2 concentration. Mechanisms for the enhanced sensing and abnormal phenomena are well explained based on density function theory calculations. Such P-N sensing switch in a single sensor here opens up interesting possibilities for the highly sensitive and selective detection of NO2 with 2D metal dichalcogenides.