N-doped carbon dots/SnS2 heterostructures for ultra-fast and sub-ppb-level detection of NO2 in multiple environments

Abstract

Nitrogen dioxide (NO2) is one of the most common toxic gases, which not only impairs human health but also produces secondary pollutants induced by sunlight via associated photochemical reactions. Herein, we design a high-performance NO2 sensor based on the N-doped carbon dots/SnS2 (N-CDs/SnS2) heterostructure using density functional theory (DFT) calculations. The DFT results approve that the decoration of N-doped carbon dots (N-CDs) onto the SnS2 nanosheet enhances adsorption capacity and electron transportation compared with those of pure SnS2, significantly enhancing the sensing responses. In addition, these in-situ synthesized N-CDs onto SnS2 nanosheet leads to band alignment, thereby significantly improves conductivity and enhances transportation and storage properties of carriers via a synergistic interaction. Furthermore, employment of UV illumination significantly increases active adsorption sites and enhances response and recovery kinetics. As a result, the developed NO2 sensor achieves fast responses of a few seconds and a limit of detection down to sub-ppb-level with the help of UV illumination. It also shows good linearly, operated in both air and oxygen-free environments, at both room or low temperature (238 K) conditions. The developed multi-framework offers an efficient and precision detection of NO2 with ultrafast responses and ultralow concentrations in multiple environments.