Cheng Zou, Yi Chen, Hongping Liang, Jianyi Chen, Yan Zhu, Mengqing Wang, Xinke Jiang, Yong He, Yong Zhou
Metal oxide-based chemiresistive gas sensors have been frequently employed for hydrogen sulfide (H 2 S) gas detection in the fields of environmental protection, food quality monitoring, and individual healthcare, but are hindered by unsatisfactory sensitivity, poor selectivity, and operational instability, especially at the ppb level. To overcome these issues, microhot plate chip-based H 2 S sensors featuring electrospun Au nanoparticle (NP)-decorated tin oxide nanotubes (SnO 2 NTs) as the sensing layer were leveraged in this work. With respect to the pristine SnO 2 counterpart, the Au/SnO 2 composites with a molar ratio of Au to Sn of 0.15 mol % (Au/SnO 2 -3) delivered the optimal performance in terms of 36-fold stronger response (53.9 vs 1.5) and quicker recovery speed (51 vs 168 s) toward 1 ppm of H 2 S, 2 orders of magnitude more sensitivity (0.057 vs 0.00017/ppb) over the concentration range of 0.1–2 ppm, and favorable H 2 S selectivity at a relatively low temperature of 130 °C. Besides, an experimental limit of detection (LoD) of 100 ppb and excellent repeatability were demonstrated. To further mitigate humidity interference, a poly(lactic acid) (PLA) film was employed to physically isolate moisture from the sensing layer and effectively suppress the response degradation due to relative humidity (RH). Although the response was still weakened due to the barrier effect, good selectivity was retained. Au incorporation resulted in a larger specific surface area, more oxygen vacancies, and an additional sensitization effect, eventually leading to improved performance. Also, the PLA film-encapsulated Au/SnO 2 -3 sensor was adopted for on-site freshness detection of broken eggs and demonstrated a benign application potential.