Defect engineering of nanostructured ZnSnO3 for conductometric room temperature CO2 sensors

Slow response/recovery kinetics and high limit of detection (LOD) are crucial challenges for practical room-temperature carbon dioxide (CO2) gas sensor platforms. Herein, visible light-excited ZnSnO3 three-dimensional nanostructures are utilized for highly sensitive and selective detection of CO2. The sensing per-formance reveals that fine-controlled oxygen vacancy (OV) and highly-active electron transition of defect-rich nanomaterials are obtained via modulating the hydrogen treatment duration, conducive to the prominently enhanced ppm-level CO2 response with low LOD (3.05 ppm), ultrafast response time (16.814 s) and improved stability (14.658 +/- 2.339 @ 400 ppm for 14 days) among all the reported ternary metal oxide semiconductor (TMOS)-based gas sensors. The photophysical enhancement mechanism of analyte is discussed in detail by combining experimental and theoretical investigation through the effect of photoexcitation on both adsorbed CO2 molecules and sensing materials, the role of pre-adsorbed oxygen for regulating targeted gas interaction, the changes of electronic transition in the bandgap, the impact of in-plane OV and bridging OV on CO2 sensing, and the function of OV for modifying the coordination sites and geometry of metal cations at the surface. From a broader perspective, the fabricated sensor provides a remarkably facile and effective technique for rapid and repeatable CO2 monitoring.