Hard-Template Synthesis of Inverse Opal Macroporous NiO-SnO₂ Heterojunction for Enhanced Acetone Detection

Chemiresistive gas sensors have emerged as a promising technology for gas detection, due to their real-time response, low costs, high sensitivity, excellent stability, and facile fabrication. However, the full realization of their potential is currently constrained by the scarcity of sensing materials capable of delivering high selectivity and ultrafast response. In this study, we prepared a three-dimensional inverse opal macroporous SnO₂ doped with NiO (3DIO NiO-SnO₂). The macroporous structure of 3DIO NiO-SnO₂ exhibits a larger specific surface area, which facilitates the diffusion and adsorption and desorption of acetone gas within the material. Furthermore, the formation of a p-n heterojunction substantially accelerates electron transport rates at the interfaces within the material. The 3DIO NiO-SnO₂ sensor demonstrates a response value of 202 to 100 ppm of acetone, which is 12 times higher than that of the SnO₂ sensor. Moreover, the 3DIO NiO-SnO₂ sensor exhibits fast response kinetics to acetone. At the optimal operating temperature of 198.5 °C, the response time to acetone gas is only 3 s, along with excellent repeatability and long-term stability. This work offers novel insights into the design strategy for macroporous NiO-SnO₂ nanomaterials, enabling high-performance quantitative detection in acetone gas sensors.