Highly sensitive ethylene glycol gas sensor based on SnO2/ZnO heterojunction composites

Ethylene glycol (EG), widely used in industry, poses severe health and environmental risks even at low concentrations, necessitating the development of highly sensitive gas sensors. Although ZnO and SnO₂ are promising semiconductor metal oxides for gas detection, their single-component limitations hinder optimal performance. This work focuses on SnO₂-decorated ZnO nanosheets, where a heterojunction structure is constructed to overcome individual material drawbacks. The aim is to enhance EG detection performance through compositional tuning and interface engineering. SnO₂/ZnO composites with varying SnO₂ contents were synthesized via a one-step hydrothermal method and systematically evaluated. The SnO₂/ZnO-1 sample (1:1 M ratio) exhibited the best performance, achieving a response of 169.89 to 100 ppm EG at 240 °C, a detection limit as low as 158 ppb, high linearity (R² = 0.99593), and strong repeatability and selectivity. Structural characterizations confirmed the successful formation of an n–n heterojunction and increased surface area and mesoporosity, enhancing gas adsorption and electron transfer. XPS revealed a higher proportion of adsorbed oxygen (30.21 %) in the composite versus pure ZnO (27.28 %), contributing to better reactivity. This research demonstrates that tailoring heterostructure interfaces and material morphology significantly improves gas sensing performance, offering a promising strategy for reliable and real-time EG detection in environmental and safety monitoring.