Three-Dimensional Inverse Opal WO ₃ /g-C ₃ N ₄ Gas Sensor for Accurate and Selective Acetone Detection in Exhaled Breath

Developing gas sensors that achieve high sensitivity, a low detection limit, and superior selectivity continues to be a critical challenge for the detection of acetone in exhaled breath. Metal oxide semiconductors (MOS) are extensively utilized in chemiresistive gas sensors, largely because of their distinguished gas sensing performance and tunable physicochemical properties. However, unmodified MOS nanostructures are prone to aggregation and lack an effective mechanism for efficient charge separation, thus exhibiting the features of limited specific surface area, low porosity, and sluggish charge migration rate, which deteriorates gas sensing performance. In this study, we employed the impregnation method and sacrificial template method to prepare a three-dimensional inverse opal (3DIO) WO 3 composite loaded with graphitic carbon nitride (g-C 3 N 4 ). This composite shows outstanding acetone sensing capability. Specifically, it achieves a response of 7.33 at 10 ppm, a detection limit of 65 ppb, favorable selectivity, and reliable stability. Such superior sensing behavior benefits greatly from the synergistic effect of abundant active sites endowed by its unique 3D ordered macroporous structure and accelerated interfacial charge transfer from the n-n heterojunction formed between WO 3 and g-C 3 N 4 . Consequently, the construction of WO 3 /g-C 3 N 4 composites with a three-dimensional ordered macroporous architecture offers a promising strategy for real-time and accurate acetone detection, as well as for the development of portable breath analysis sensors.