Ultrasensitive room temperature ppb-level NO2 gas sensors based on SnS2/rGO nanohybrids with P-N transition and optoelectronic visible light enhancement performance

Nitrogen dioxide (NO2) is an important gas for industrial production, medical treatment and biology. At present, the detection of ultralow concentrations (ppb levels) of NO2 at low temperature in the presence of other interfering gases is still a great challenge. In this study, we developed nanohybrids of SnS2 and reduced graphene oxide (SnS2/rGO) as gas sensors by a simple one-step hydrothermal method. In particular, the sensors exhibited transitions in the p-type and n-type sensing behavior towards NO2 as a result of adjusting the ratio of rGO to SnS2. Both types of sensors demonstrated remarkable LOD values of 5.03 ppb and 1.10 ppb, and sensitivities of 650% and 40% at 1 ppm, respectively. Fast response and strong selectivity were also realized at room temperature. The ability of the sensors to be manipulated by visible light and the influence of light density and wavelength were investigated in particular. Red light (650 nm) with 1 mW cm(-2) can greatly enhance the sensitivity by around five-fold, and significantly accelerate the recovery rate, and a complete response and recovery curve with good sensitivity to 10 ppb NO2 was realized. Further, ab initio DFT calculations and the band structure of the nanohybrids explain the interaction of the components and the effect of the light-induced carriers on gas-sensing behavior.