Defect-heterointerface synergy in CuO/S-SnO₂ heterostructures for highly sensitive n-butanol detection

Sensitive detection of volatile organic compounds (VOCs) such as n-butanol is of great significance for environmental monitoring and industrial safety. In this study, a CuO/S-SnO₂ heterostructure composed of flower-like microspheres was successfully fabricated via a hydrothermal process combined with a thermal in-situ replacement strategy. Structural and chemical analyses reveal that sulfur incorporation induces lattice distortion and defect states in SnO₂, while the introduction of CuO forms a p-n heterojunction at the interface. Compared with pristine SnO₂, the optimized sensor delivers a high response of 26 toward 100 ppm n-butanol at a relatively low operating temperature of 180 °C, along with good selectivity, repeatability, long-term stability, and enhanced humidity tolerance. The theoretical detection limit is estimated to be 13.3 ppb based on the linear response-concentration relationship. The enhanced sensing behavior is attributed to the synergistic effects of defect-induced active sites and heterointerface-modulated charge transport. Sulfur incorporation is found to increase the density of surface-adsorbed oxygen species and active sites, while the formation of the CuO/SnO₂ heterojunction facilitates interfacial charge transfer and modulates the electron depletion layer. This work provides an effective strategy for improving VOC sensing performance through the synergistic regulation of defect engineering and heterointerface construction.