UV excited gas sensing SnO2-ZnO aerogels to ppb-level ethanol detection

[Display omitted] •3D SnO2-ZnO aerogels were synthesized by two-step reactions and annealing.•SnO2-ZnO aerogels can detect ultra-low ethanol concentration as 10 ppb with UV excitation.•The pore structure, tensile strain and well-planned bandgap help aerogels reduce minimum analytical limit. Gas-sensing materials that can detect ultra-low gas concentration at ppb level have attracted widespread attention. In order to reduce minimum detectable limit, on the one hand, we synthesized 3D SnO2-ZnO aerogels by two-step reactions and annealing process. On the other hand, we utilized UV light to motivate lower response concentration. SnO2-ZnO aerogels exhibit ultra-low response concentration as 10 ppb to ethanol at 300℃ under UV irradiation. In this condition, their response time (∼2 s), recovery time (∼37 s) and stability (within 14 days) also represent that SnO2-ZnO aerogels are suitable for gas sensors. Lastly, ethanol-sensing mechanism indicates that the following aspects help SnO2-ZnO aerogels to detect ultra-low ethanol concentration under UV irradiation: (i) adequate mesoporous structure increases active sites, facilitates ethanol transfer and improves UV utilization; (ii) tensile strain enables aerogels to absorb more abundant UV energy and then produce available photo-electrons in ethanol atmosphere; (iii) well-planned bandgap structure (SnO2 grain, ZnO grain and n-n heterojunction) can also provide more photo-electrons to reduce resistance in ethanol atmosphere.