UV light activated NO2 gas sensing based on Au nanoparticles decorated few-layer MoS2 thin film at room temperature

Nitrogen dioxide (NO2) plays a key role in environmental protection and human health. Recently, molybdenum disulfide (MoS2) representative of novel 2D materials has been utilized to detect NO2 gas, still hindered by the weak response, high operation temperature, as well as poor recovery characteristics. Herein, we report a UV light-assisted, room-temperature, recoverable, sensitive and selective NO2 gas sensing based on few-layer MoS2 nanosheet-Au nanoparticle composites serving as the sensing layer. In the dark condition, the as-prepared MoS2-Au sensor showed a response of 10% toward 2.5 ppm NO2 more than two times larger than MoS2 one, arising from more reaction sites (spillover effect and produced interfaces) and smaller baseline resistance after Au incorporation. Undesirably, all sensors exhibited an incomplete recovery. When MoS2-Au sensors were exposed to NO2 gas under UV illumination, better performance in terms of three-time enhanced response, full recovery and favorable repeatability was achieved in comparison with that in the dark case. Two aspects were responsible for these phenomena. On one hand, additional photoinduced charge carriers ensured sufficient gas-solid interactions between sensing layer and target molecules, thereby resulting in a larger response. The other aspect lay in effective separation of these charge carriers at MoS2/Au interfaces, contributing to recoverable and repeatable reactions. MoS2-Au composites were adopted for NO2 detection under UV illumination and exhibited a promising capacity of UV photodetector as well as an inspiring room-temperature gas detection, which provided an alternative strategy to design a single optoelectronic device with multi-functions.