Down to ppb level NO2 detection by vertically MoS2 nanoflakes grown on In2O3 microtubes at room temperature

Metal oxide-based gas sensors have advantages over electrochemical sensors of small size, low cost, and longer utilization life, but their performance in detecting ppb-level NO2 is compromised at room temperature (RT). In this work, a p-n MoS2-In2O3 heterojunction was constructed by in situ vertically growing MoS2 nanoflakes on the surface of In2O3 microtubes. The In2O3@MoS2 composite with a 25 % mass rate of MoS2 presents an outstanding sensing performance with a response of 39.4 to 1 ppm NO2 at RT. The response and recovery time are 72 s and 118 s, respectively, and the detection limit is 115.4 ppb. The enhanced NO2 sensing performance may benefit from p-n heterojunction at the MoS2-In2O3 interface, the increased oxygen vacancies and chemisorbed oxygen, and the unique structure. The exposed sulfur active sites and chemical bonds introduced from MoS2 also contribute to the excellent gas sensor performance. Thus, this work proved that the In2O3@MoS2 sensor is a promising material for detecting trace NO2 at RT.