Light-enhanced gas sensing of ZnS-core/ZnO-shell nanowires at room temperature

ZnS-core/ZnO-shell nanowires were synthesized by the thermal evaporation of ZnS powders followed by the atomic layer deposition of ZnO and then multiple networked ZnS-core/ZnO-shell nanowire gas sensors were fabricated. The morphology, crystal structure, and sensing properties of pristine ZnS nanowires and ZnS-core/ZnO-shell nanowires to NO₂ gas at room temperature under ultraviolet (UV) illumination were examined. Pristine ZnO nanowires and ZnS-core/ZnO-shell nanowires showed responses ranging from ~236 to ~620 % and from ~439 to ~1,180 %, respectively, to 1–5 ppm NO₂ under UV (254 nm, 1.2 mW/cm²) illumination, corresponding to increases by 2.3–5.8 and 3.8–10.2 times, respectively, compared to the responses in the dark. These results imply a synergistic effect of a combination of UV irradiation and core-shell nanostructures formation on the gas sensing properties of ZnS nanowires. The underlying mechanism for the enhanced gas sensing properties of ZnS-core/ZnO-shell nanowires toward NO₂ gas under UV illumination is discussed.