Light-activated ultrasensitive NO2 gas sensor based on heterojunctions of CuO nanospheres/MoS2 nanosheets at room temperature

MoS2-based gas sensor has become an effective platform to detect NO2 gas. However, room-temperature NO2 gas sensor based on MoS2 are facing low sensitivity and poor response/recovery behaviors because of low-reacting activity between gas-sensing materials and NO2 gas at room temperature. Purposefully, a room-temperature NO2 gas sensor based on CuO/MoS2 heterojunctions with excellent sensitivity and fast response/recovery speeds is successfully realized. More attractively, the CuO/MoS2-3 sensor exhibits remarkable response (8.98) and short response/recovery time of 18.5/53.5 s to 10 ppm NO2 at room temperature under red light illumination, which is obviously better than that under dark. The improved sensitivity and fast response/recovery behaviors are attributed not only to the charge separation efficiency derived from the effect of heterojunctions, but also to the charge flow on the sensing layer in the context of NO2/MoS2/CuO interaction under red light illumination. In addition, the fabricated sensor has low detection limit (50 ppb), excellent reversibility and high selectivity to NO2 against other gases. After 40 days, the CuO/MoS2-3 sensor still maintains a relatively stable response with the fast response time (<18.5 s) under red light illumination, ensuring a long-term and fast detection to NO2 in practical applications.