Facile synthesis of porous Au-decorated SnO2 microflowers with abundant oxygen vacancies for trace VOCs detection

Hierarchical Au-decorated SnO2 (Au@SnO2) microflowers with a porous structure were successfully synthesized. The preparation process involves in a hydrothermal method, calcination treatment, as well as modification. The hierarchical structure consisted of a large number of porous, uniform nanosheets. Excellent gas-sensing performances were demonstrated by the gas sensors fabricated using Au@SnO2 microflowers, for detecting volatile organic compounds (VOCs). In particular, for the accurate and fast detection of formaldehyde, the 2%Au-decorated SnO2 microflowers sensors showed a strong sensing response (76.5) for formaldehyde (100 ppm) at 140 °C, approximately three times higher than that (28.2) observed for the pure porous SnO2 microflowers. The response and recovery times (10 s/16 s) were shorter than those (12 s/25 s) of the pure SnO2, respectively. The detection limit for the 2%Au@SnO2 sensor was 19.03 ppb. The sensing mechanism of Au@SnO2 sensors was also investigated. Favorable porous 3-dimensional structure, high catalytic activity, and electron sensitization effect of Au nanoparticles (NPs) improved the gas-sensing performance. Furthermore, the catalytic activity of Au NPs was maximized due to their uniform distribution on the surface of each porous SnO2 nanosheet. The Au-decorated SnO2 microflowers sensors have great potential for the accurate, fast, and highly sensitive response detection of formaldehyde gas.