Effect of layer number on recovery rate of WS2 nanosheets for ammonia detection at room temperature

Tungsten disulfide (WS 2 ), as a representative layered transition metal dichalcogenides (TMDs), is expected as a promising candidate for high-performance NH 3 sensor at room temperature. Unfortunately, the common WS 2 based NH 3 sensors are difficult to recovery at room temperature, which severely limits its application. Hence, how to improve recovery has become an urgent problem to be solved. Herein, we prepare five types of WS 2 nanosheets with different layer numbers from bulk to monolayer, and find that the recovery time of NH 3 gas sensor is rapidly linear shorten as the number of layers decreasing. Through the first-principles calculation of the interaction between NH 3 and WS 2 substance, the different binding energy between ammonia and the surface (−0.179   eV) and interlayer (−0.356   eV) of layered WS 2 , as well as the different electron transfer way, should be responsible for the difficult recovery rate of various WS 2 samples. Therefore, reducing the number of layer of WS 2 is a promising approach to speed up recovery. Based on this conclusion, we successfully prepare a fast recoverable ammonia gas sensor based on single layer WS 2 , which exhibits exciting fast recovery within 271.9   s at room temperature without any condition. Moreover, our work also can act as a reference for other gas detection of TMDs based gas sensor to improve the gas performance at room-temperature.