Ultrasensitive, Selective, and Reversible Room-Temperature NO2 Sensor Based on a Monolayer Transition Metal Dichalcogenide

Chemical sensors are essential for environmental and health monitoring. In particular, gas sensors that can efficiently detect toxic gases emitted from power plants, vehicles, and industrial sources at room temperature, are of substantial importance. Here, we demonstrate a room-temperature NO₂ sensor based on a monolayer transition metal dichalcogenide that is highly sensitive and selective. Depending on the layer number of the sensing devices, their electrical resistances substantially increase or decrease upon exposure to NO₂. We find the atomically-thin sensors to be strongly selective to NO₂ with only minimal responses to NH₃, CH₂O, and CO₂. Importantly, the monolayer sensor shows complete reversibility with fast recovery in ambient condition (i.e. at room temperature and under substantial relative humidity). Combined with theoretical calculations, we explore interactions between different molecular species and the monolayer crystal and discuss the underlying sensing mechanism.