UV-light-enhanced room temperature NO2 gas-sensing performances based on sulfur-doped graphitic carbon nitride nanoflakes

Abstract

Two-dimensional graphitic carbon nitride (g-C₃N₄) has generated tremendous attention in room temperature (RT) gas-sensing applications because of its physicochemical characteristics. Especially, due to its tunable electronic structure, g-C₃N₄ nanostructure induced by intrinsic doping has proved to be a potential candidate for RT NO₂ gas sensors. In this work, pristine g-C₃N₄ nanoflakes (M-GCN) and sulfur-doped g-C₃N₄ nanoflakes (T-GCN) were successfully synthesized using melamine and thiourea for RT NO₂ gas detection. The T-GCN sensor produces excellent sensitivity of 13.35% and selectivity for NO₂ gas (100 ppm) at RT as compared to M-GCN sensor responses. Fascinatingly, under the UV light illumination (365 nm), the sensitivity of the T-GCN sensor exhibited a significant enhancement by 37.7%, which was ∼2.81-fold times with high selectivity, fast response/recovery times, (81 s/69 s) and long-term stability, as compared to the dark condition. The higher gas sensing performances under UV light could be ascribed to the effective generation of abundant charge carriers that further lead to improving the sensitivity and selectivity of the T-GCN sensor. Moreover, the enhanced functional groups, defect sites, porosity, and high surface area of T-GCN resulted in augmented sensing performance in both dark and UV light conditions. The route of nanostructure-induced intrinsic doping to improve the gas sensing fidelity could provide new insights for the development of RT gas sensing applications.