Enhancing the Gas Sensing Performance of NO2 Sensors at Low Temperatures via 3D Ordered Macroporous Structures and Organic–Inorganic Heterogeneous Interfaces

The development of highly sensitive and rapid response/recovery NO2 sensors that can operate at low temperatures (below 100 °C) and room temperature (RT) holds significant scientific value, yet it remains challenging. Inspired by the macroporous structure of butterfly wings in nature, this work significantly enhances the gas-sensing performance of NO2 sensors at low temperatures through the synergy of vortex effects in the ordered macroporous structure of three-dimensional inverse opal (3DIO) and the engineering of organic-inorganic heterojunctions. 3DIO ZnFe2O4/PANI (ZFOP) composites were synthesized via the sacrificial template method and in situ polymerization. Computational fluid dynamics (CFD) simulations revealed that the ordered macropores can induce vortex effects, which effectively reduce gas flow velocity and prolong the duration of surface interactions, thereby enhancing sensitivity. The organic-inorganic heterointerfaces formed between ZnFe2O4 and PANI can effectively stabilize the polymer chains, improve mechanical robustness, and profoundly modulate the electronic properties of the composite. Experimental results demonstrated that the 3DIO ZFOP sensor exhibits ultrahigh response values toward 100 ppm NO2 (SR1 = 242.6 at 98 °C, SR2 = 4.51 at RT) with an ultrafast response speed of 2 s. Furthermore, the 3DIO ZFOP sensor delivered outstanding selectivity, superior repeatability, and long-term stability. Density functional theory (DFT) calculations verified that the substantial charge transfer during the adsorption process strengthens the adsorption interactions toward NO2. This work provides a highly promising strategy for the facile fabrication of low-power NO2 sensors with high sensitivity and rapid response/recovery rates.