Variable gas sensing performance towards different volatile organic compounds caused by integration types of ZnS on In2O3 hollow spheres

This study reports various integration types of In2O3/ZnS composites as high-performance sensing materials to different volatile organic compounds. By adjusting the molar ratios of In2O3 to ZnS, two optimized structures were prepared via two-step hydrothermal methods, e.g., the ZnS nanoparticles (similar to 10 nm) modified In2O3 hollow spheres (at the molar ratio of 1:0.1) and the In2O3@ZnS core-shell hollow spheres (at the molar ratio of 1:1). These two kinds of structures exhibit different sensing responses towards n-butylamine and n-butanol respectively, in comparison with other target gases (e.g. ethanol, methanol, isopropanol, and formaldehyde). Specifically, the ZnS nanoparticles modified In2O3 hollow spheres show a good response (5.8) to n-butylamine at the optimized working temperature of 300 degrees C while the In2O3@ZnS core-shell structures exhibit a high response (8.6) towards n-butanol at 260 degrees C. DFT simulation was used to reveal the reason for the long recovery time by calculating the adsorption energies between ZnS (110) and the target molecules. The enhanced gas sensing property is attributed to the unique structure of the materials and the formation of heterojunction between In2O3 and ZnS. This research provides a reference for developing high-performance gas sensors from the perspective of composite selection and structure design.