MoO Pump-Enhanced Flexible TiO Nanojungle-Based Chemiresistors for Rapid Room-Temperature Detection of HS at Parts-per-Billion Levels.

In this study, we developed a gas sensing platform that can sensitively and specifically detect trace HS in a high-humidity atmosphere at RT. Upon integrating a carbon nitride (CN) nanofilm and molybdenum dioxide (MoO) nanosheets onto nanojungle-like TiO nanotube arrays (TiNTs), the fabricated chemiresistor showed rapid response (38 s)/recovery (58 s) abilities and remarkable detection sensitivity for HS at concentrations down to 2 ppb, with an estimated detection limit of 1.13 ppb at RT and room-environmental light (REL). Importantly, the gas sensor exhibited satisfactory HS sensing performance even in dark conditions with a response of 1.9 at 200 ppb. In this design, apart from the architectural advantages of the nanojungle-like TiNTs for accelerating the gas flow efficiency and the abundant sensing sites provided by the CN film, the MoO nanosheets act as the essential electron pump not only for the HS response but also for the subsequent recovery process in air. After employing the MoO pump onto CN/TiNTs, the response time and recovery time of the system are shortened to ∼35 and ∼11%, respectively. Moreover, we demonstrated the good performance of the flexible gas sensor in detecting trace HS in human exhaled breath with good humidity resistance. These results highlight the possibility of designing chemiresistors operating in RT and REL conditions and to use these environmentally friendly TiO-based sensors in real applications.