Enhanced formaldehyde sensing performance employing plasma-treated hierarchical SnO₂ nanosheets through oxygen vacancy modulation

Effective utilization of nanostructured metal-oxides with surface engineering is often overlooked during fabrication of gas sensors. The paper reports preparation of flower-like tin oxide nanosheets (average thickness = 12 nm) enriched with oxygen vacancies towards enhanced formaldehyde detection. The proportion of oxygen vacancy was increased using argon-plasma treatment (power = 100 W) with varied time durations (0, 2, 4, 7, 10 min). A detailed material characterization confirmed the structural property and oxygen vacancy content in the samples. A comparative sensing performance was analyzed among different fabricated sensor devices based on plasma exposure duration. Superior sensing behavior was registered from sensor S_7 comprising of sample with 7 min plasma exposure having maximum oxygen vacancy content of 53.16 % (relative). Sensor S_7 was considered optimum, which showed a response of 24.19 in presence of 10 ppm of formaldehyde which was 8.6 times greater than the sensor (S_0) without plasma exposure. Remarkably, sensor S_7 exhibited high sensitivity, fast kinetics, excellent reversibility, notable repeatability, and admirable selectivity, along with 34 ppb as limit of detection. Additionally, the sensing mechanism is adequately discussed based on the surface interaction, electronic sensitization and associated redox reactions. The demonstrated work emphasizes an efficacious approach toward developing upgraded gas sensor devices for widespread applications.