Nitrogen-doped graphene quantum dots-modified mesoporous SnO2 hierarchical hollow cubes for low temperature detection of nitrogen dioxide

The exploration of nitrogen dioxide (NO2) gas sensor with high response, fast response and recovery speed, and low working temperature is still an urgent challenge. In this work, a novel SnO2 hierarchical hollow cube composed of ultrathin mesoporous nanosheets was successfully prepared via a simple sulfidation-oxidation method, and nitrogen-doped graphene quantum dots (N-GQDs) were evenly modified on the surface of SnO2. The prepared N-GQDs modified SnO2 (NG/Snx) shows an improved response, and the optimal sample (NG/ Sn1.5) response (Rg/Ra = 417) toward 1 ppm NO2 is approximately 2.2 times that of pure SnO2 at 130 ?C. Moreover, the NG/Sn1.5 sensing material exhibits fast response and recovery speed, good selectivity, repeatability, and long-term stability. More attractively, the NG/Sn1.5 sensor has outstanding detection ability (Rg/ Ra = 25.3) for low concentration NO2 (100 ppb). The significantly improved NO2 sensing performance of NG/ Sn1.5 sensing material is mainly attributed to the zero-dimensional/three-dimensional (0D/3D) heterostructure construction and N doping, which increases the space charge modulation depth and NO2 adsorption active sites of the composite material. In addition, the mesoporous hierarchical cubic structure is beneficial to the improvement of NO2 sensing performance due to its stable gas diffusion channels, large specific surface area, and abundant nanoscale grain boundaries. The results obtained herein may provide new ideas for the preparation of high performance NO2 sensors at low temperatures.