Zero-dimensional heterostructures: N-doped graphene dots/SnO2 for ultrasensitive and selective NO2 gas sensing at low temperatures

Abstract

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 (R_g/R_a = 292) with a short 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 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.