Ultra-sensitive ethanol detection using a chemiresistive SnO₂ thin-film gas sensor functionalized with RuO₂ nanosheets

This study presents the design and fabrication of a ruthenium dioxide (RuO₂) nanosheets-functionalized tin dioxide (SnO₂) thin-film gas sensor integrated with a microheater in a suspended membrane structure. The RuO₂ nanosheets are synthesized via an intercalation-driven exfoliation process and subsequently deposited onto a sputtered SnO₂ thin film. Due to the catalytic properties and high surface-to-volume ratio of RuO₂ nanosheets, the functionalized sensor demonstrates a 337% increase in response (R_air/R_gas) to 10 ppm ethanol compared to pristine SnO₂ thin film. The sensor achieves sensitive detection from a few parts-per-million (ppm) down to several parts-per-billion (ppb) concentrations of ethanol. Evaluations under varied humidity conditions, as well as selectivity and 28-day stability tests, demonstrate that the RuO₂ nanosheets-functionalized sensor maintains reliable performance. These results highlight its potential as a sensitive, selective, and low-power solution for ethanol gas detection. Furthermore, the sensor successfully tracks breath alcohol concentration in real-time through controlled alcohol intake experiments, demonstrating its feasibility for practical breath alcohol detection.