Au-Decorated Sn3O4 Nanoflower-Based MEMS Gas Sensor for Detecting ppb-Level Acetone

This paper reports the synthesis and gas sensing performance of Au-decorated Sn3O4 (Au/Sn3O4) nanoflowers as gas-sensitive materials for acetone gas sensors. Sn3O4 nanoflowers were first synthesized via a hydrothermal reaction and then were decorated with Au nanoparticles by reducing the Au ions in HAuCl4. The phase structure, surface morphology, specific surface area, and surface chemical composition of the synthesized samples were systematically investigated. The morphological characterization confirmed the flower-like structures of Au/Sn3O4 samples, which were composed of Sn3O4 nanosheets and uniformly dispersed Au nanoparticles. The synthesized Sn3O4 and Au/Sn3O4 nanoflowers were applied as gas-sensitive materials in low-cost integrated microelectro-mechanical system-based acetone sensors. Among these, the Au/Sn3O4 sensors demonstrated superior performance, with a higher response (Rair/Rgas = 6.1) and faster response/recovery time (9 s/25 s) toward 5 ppm acetone gas at a low operating temperature of 160 °C compared to the Sn3O4 sensors. In addition, Au/Sn3O4 sensors also presented high selectivity to acetone gas under complex atmospheric conditions, with an extremely low detection limit of 50 ppb. The results suggest that the designed acetone gas sensors are expected for early screening and diagnosis of diabetes through monitoring the acetone gas in exhaled breath.