Synergistically enhanced room-temperature NO₂ gas sensing via Au-decorated hierarchical SnO₂ nanosheets under blue light excitation

Nitrogen dioxide (NO₂), a significant atmospheric pollutant primarily emitted from combustion processes, poses substantial environmental and health risks, underscoring the critical need for accurate detection methods. Conventional SnO₂-based sensors are typically constrained by high operating temperatures and limited sensitivity. This study overcomes these limitations by introducing a novel approach that combines noble metal modification with bandgap-matched light excitation, enabling high-performance NO₂ detection at room temperature. Au/SnO₂ composites with hierarchical nanosheet architectures were synthesized via hydrothermal and impregnation methods, as confirmed by SEM. Their sensing properties were systematically investigated under blue light excitation. Among the samples tested, the 2.5 wt% Au/SnO₂ sensor demonstrated superior performance, exhibiting a remarkable response (149.25 @ 5 ppm), a low detection limit (150 ppb), and excellent selectivity, long-term stability, and humidity tolerance at room temperature. First-principles calculations reveal that the enhanced sensor performance originates from a synergistic effect between Au nanoparticle decoration, which enhances NO₂ adsorption and charge transfer, and the additional photogenerated carriers induced by blue light excitation. This study provides novel material design insights for developing high efficiency room temperature NO₂ sensors.