Switching Effect of p-CuO Nanotube/n-InS Nanosheet Heterostructures for High-Performance Room-Temperature HS Sensing.

High operating temperature and low response restrict the application of HS sensors. Due to the strong chemical affinity of CuO to HS and the large band gap and high stability of β-InS, CuO nanotube/InS nanosheet p/n heterostructures have been delicately designed for binder-free gas sensors by a facile method consisting of sputtering, chemical etching, and annealing. A switching effect of HS concentration on the response of CuO/InS gas sensors has been observed. When exposed to low-concentration HS (1-10 ppm), the response is less than 0.10 and dominated by the surface-type adsorption-desorption process between CuO and HS. When exposed to high-concentration HS, the sensor exhibits a superior response of 3511 toward 50 ppm HS, considerable selectivity, and long-term stability at room temperature. This dramatically enhanced response can be explained by the transformed junction from the CuO/InS heterojunction to the CuS/InS Schottky junction. These results suggest that the binder-free ceramic tube-type CuO/InS gas sensor with considerable performance will have promising potential for HS gas detection. Moreover, this method provides an effective strategy to fabricate other binder-free gas sensors.