Highly sensitive NO2 response and abnormal P-N sensing transition with ultrathin Mo-doped SnS2 nanosheets

Abstract

Ultrathin Mo-doped SnS 2 nanosheets have been synthesized via a facile solvothermal method, demonstrating the enhanced response and abnormal P-N sensing transition for highly sensitive and selective trace NO 2 detection. • Facile synthesis of ultrathin Mo-doped SnS 2 nanosheets is demonstrated. • Enhanced NO 2 sensing properties are achieved for SnS 2 nanosheets upon Mo doping. • Abnormal P-N sensing switch is discovered for the first time for metal sulfides. • Mechanisms for the enhanced and abnormal NO 2 sensing were clearly elucidated. Sensing of Nitrogen dioxide (NO 2 ) 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 NO 2 detection with fast response, high sensitivity and good selectivity. In this work, two-dimensional (2D) ultrathin n-type SnS 2 nanosheets with Mo doping have been synthesized via a simple single-step solvothermal method and exploited for NO 2 sensing application. Phase and structural analyses confirm the homogeneous cation alloying of Mo (1% ~ 10%) in the SnS 2 . It is indicated that the Mo doping can elegantly tune the electronic structure of SnS 2 and promote the sensing process with negative adsorption energy. Especially for 3%Mo-SnS 2 nanosheet, the NO 2 sensing response at 150 ℃ has been enhanced around 23 times relative to the un-doped SnS 2 sample, together with fast sensing kinetics and good NO 2 selectivity. Interestingly, the n-type SnS 2 -based sensor shows an abnormal response characteristic for the first time with resistance decrease at low NO 2 concentration, behaving like a p-type semiconductor. The P-N sensing transition can be regulated by varying the operation temperature and NO 2 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 NO 2 with 2D metal dichalcogenides.