Zero-dimensional Heterostructures: N-Doped Graphene Dots/SnO2 for Ultrasensitive and Selective NO2 Gas Sensing at Low Temperatures

To enable the sensitive and selective monitoring of NO2 gas at low ppb concentrations, zero-dimensional N-doped graphene dot/SnO2 quantum dot (N-GD–SnO2) heterostructures are prepared via a simple wet-chemical method. In comparison with pristine SnO2, our fabricated device exhibits an enhanced response (Rg/Ra = 292) with fast response (181 s) and recovery time (81 s) toward 100 ppb NO2 gas at 150°C; furthermore, the response increases to 4336 as the temperature decreases to 50°C. The sensor also exhibits the distinct capability to detect NO2 with an ultralow concentration of 20 ppb with high response. This dramatic enhancement is attributed to enhanced electron transfer from SnO2 to N-GDs and to stronger adsorption of NO2 molecules onto the N-GDs’ surface. Additionally, zero-dimensional morphology also helped to enhanced sensing performance due to large surface area, more active sites and better nanoscale interface. Finally, the sensor exhibits the characteristics of excellent selectivity toward NO2 over other gases (SO2, H2S, CO, and NH3). Thus, our research provides a new approach toward zero-dimensional heterostructures for gas-sensing applications.