All-dry transferred ReS2 nanosheets for ultrasensitive room-temperature NO2 sensing under visible light illumination

For gas sensing applications, most of the reported two-dimensional (2D) materials are suffering from relatively low sensitivity and high limit of detection (LOD) at room temperature. In this work, we selected rhenium disulfide (ReS2) nanosheets to fabricate ReS2 transistor-based gas sensors (RTGSs) with ultrahigh sensitivity and low LOD toward nitrogen dioxide (NO2). The ReS2 nanosheets with different thicknesses were prepared via mechanical exfoliation and all-dry transfer method. Under 405 nm light illumination at room temperature (25 °C), the fabricated gas sensors showed a significant enhancement of the response with full reversibility toward ppb level NO2 (response of 9.07 at 500 ppb, a LOD of 50 ppb). In particular, the total response and recovery time of the RTGS was revealed to be less than 4 minutes (55 and 180 s, respectively), which is one of the top three shortest response and recovery times toward ppb level NO2 of the reported 2D material-based room-temperature gas sensors so far. Via Raman spectrometry, Kelvin probe force microscopy (KPFM), and X-ray photoelectron spectrometry (XPS), the structure and gas sensing mechanism of the materials were systematically investigated. It was confirmed that the electrons transfer from the ReS2 surface to NO2 molecules, inducing the hole doping of ReS2, which consequently increased the sensor resistance. Moreover, the concentration of the photogenerated carriers in ReS2 would accordingly be promoted by light illumination, which accounts for the substantial light enhancement of the gas sensing performance of RTGSs.