Optimized nanostructured In2O3 gas sensors: harnessing annealing-induced defects and oxygen vacancies for ultra-sensitive and selective H2S detection at trace levels†

Achieving selectivity and high sensitivity for specific analytes at trace levels remains a significant challenge for chemiresistive gas sensors. In this study, nanostructured indium oxide (In₂O₃) gas sensors were synthesized via spin coating for detection of hydrogen sulphide (H₂S) gas at trace levels. The influence of annealing temperature on the gas sensing performance for the deposited nanostructured gas sensors was systematically investigated. The sensor annealed at 350 °C exhibited outstanding performance, with rapid response time of (17 ± 1) seconds for H₂S gas concentrations of 4 ppm, at an optimal operating temperature of 250 °C. Additionally, it achieved an exceptional sensing response of (36.52 ± 2.02)% and (97.89 ± 0.08)% for 0.5 ppm and 4 ppm H₂S gas respectively. The remarkable sensing performance is attributed to the presence of structural defects, voids and oxygen vacancies, which enhance gas adsorption and reactivity. These findings demonstrate that In₂O₃ nanostructured gas sensors are highly effective for the reliable detection and monitoring of H₂S gas in practical applications.