Noble metal nanoparticle decorated tungsten diselenide nanosheets for ultrasensitive detection of NO2 at room temperature

•The catalytic effect of Au and Pt functionalization onto 2D WSe2nanosheets is demonstrated for NO2 gas sensing.•The response towards NO2 for functionalized sensors increased by 40 times compared to pristine WSe2 nanosheets based devices.•The sensors responded selectively in the range of 0.5–5 ppm at room temperature.•The sensor showed reversible behaviour at room temperature itself without any external stimulus.•Liquid phase exfoliation was adopted to synthesize WSe2 nanosheets. The interaction of NO2 gas with functionalized 2D WSe2 was investigated in this study. The liquid exfoliated pristine 2D WSe2 was functionalized with Au and Pt nanoparticles through reduction of respective metal salts at room temperature. The catalytic effect of nanoparticle functionalization was observed in gas sensing experiments. The results revealed the enhancement in sensing response upon decoration (R% = 170% for Au-decoration and 220% for Pt-decoration at 5 ppm NO2) at room temperature and most importantly, the recovery of the sensor was improved to less than 5 min for Au decorated WSe2. This work, therefore, successfully addressed the known bottleneck of recovery in 2D material-based NO2 sensors without utilizing any external energy stimulus. In fact, the response was found to be stable and reproducible while the sensor was subjected to repeated testing. The sensing characteristics and the underlying sensing mechanism have been explained in detail.