Selective sensing of H2S using Bougainvillea extract mediated SnO2 thin films

Hydrogen sulfide (H2S) sensing at room temperature with reliable and sensitive detection methods remains as major concern owing to its toxicity and wide range of applications. Herein, we propose a novel approach of Bougainvillea (green) extract mediated thin film synthesis for sensing of H2S at ambient operating temperature (~ 80 ± 2 °C). The structural, morphological, and sensing properties of the thin films were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), and gas sensing measurements. The XRD analysis revealed the crystalline nature of SnO2 thin films, with a predominant tetragonal rutile phase (grain size ~ 15 nm and film thickness ~ 1.32 μm). TEM and AFM observations confirmed the uniform and dense morphology of the films with surface roughness of ~ 14.8 nm suitable for gas sensing applications. XPS revealed the presence of flavonoid-derived functional groups (C–O, O–C = O), originating from the extract, which facilitated selective H₂S adsorption via sulfur–hydroxyl interactions. These bio-derived groups contributed to enhanced surface reactivity and gas sensing performance. The sensor exhibited excellent sensitivity at ~ 5 ppm with a good response and recovery time (22s/18s), and was highly selective (~ 82.41%) among other VOCs. The sensing mechanism can be attributed to the catalytic effect of Bougainvillea extract, which facilitated the adsorption and desorption of H2S molecules on the SnO2 surface. Overall, the Bougainvillea extract-mediated SnO2 thin films offer a promising platform for lower operating temperature sensing of H2S, with potential applications in environmental monitoring, industrial safety, and healthcare sectors. Further optimization and integration with electronic devices could potentially enhance their practical utility in real-world scenarios.