Urchin-like dual-shelled ZnO/SnO2 hollow spheres for ultrahigh sensitive low-temperature NO2 sensing

The semiconductor-based sensing materials with hollow and heterojunction structures were demonstrated significant advantages in critical performance metrics including sensitivity, operating temperature, and response/recovery time. In this study, the urchin-like dual-shelled ZnO/SnO 2 hollow spheres were effectively fabricated using a two-step hydrothermal approach. Compared with pure ZnO, the prepared ZnO/SnO 2 material exhibits a larger specific surface area, and abundant interface contact sites, showing significant improvements in NO 2 gas detection. Through the formation of hollow ZnO/SnO 2 heterojunctions, the optimal operating temperature has been successfully decreased from 150℃ to 65℃. Additionally, the ZnO/SnO 2 sensor exhibits a response of 449.4–10 ppm NO 2 , which is 8.7 times that of the ZnO-based sensor. Moreover, this sensor demonstrates a fast response/recovery time (47/50 s) and long-term stability of 60 days. Selective tests confirmed the high specificity of the ZnO/SnO 2 sensor to NO 2 gas (S nitrogen dioxide /S ammonia = 345.7). Additionally, the adsorption behaviors of NO 2 on the ZnO/SnO 2 heterojunction and ZnO surface were analyzed using density functional theory (DFT) calculations, providing theoretical insights for optimizing the performance of hollow core-shell structured sensors.