Optoelectronic Gas Sensor Based on Few-Layered InSe Nanosheets for NO₂ Detection with Ultrahigh Antihumidity Ability

Two-dimensional (2D) transition-metal/metal chalcogenides including MoS₂, MoSe₂, WS₂, SnS₂, etc. have shown considerable potential for the fabrication of gas sensors for NO₂ detection. However, these sensors usually suffer from sluggish and incomplete recovery at room temperature, and their sensitivities are limited by presorbed O₂. In this work, a novel optoelectronic gas sensor based on direct-bandgap InSe nanosheets was demonstrated. Because of the excellent photoelectric and sensing properties in few-layer InSe, detection of NO₂ at room temperature was realized. Ultrahigh and reversible responses were obtained under ultraviolet (UV) light illumination, and the limit of detection (0.98 ppb) was ∼40 times lower than that observed without UV light. Furthermore, the effects of O₂ and H₂O molecules on sensor performance were fully studied through experiments and density functional theory. Some new mechanisms of NO₂ detection in high relative humidity conditions under UV illumination were proposed, including regulation of proton transfer and induction of H₂O₂ reduction. In all, this work not only broadens the application field of 2D InSe, but also demonstrates the potential prospect of detecting ppb-level NO₂ in complex circumstances such as human breath by using 2D material-based sensors with light activation.