Boosting TEA sensing performance of ZnO porous hollow spheres via in situ construction of ZnS-ZnO heterojunction

Upgrading the gas sensing performance of metal oxide semiconductor (MOS) to meet the practical demands of MOS sensor for detecting various harmful gases is a significant issue in the field of environmental protection. Herein, we propose a sensitization strategy to improve the gas sensing performance of ZnO by in-situ construction of ZnS-ZnO n-n heterojunction. To expound this strategy, nanoscale ZnS-ZnO heterojunctions were homogeneously modified on self-synthesized ZnO porous hollow spheres (PHSs) by sulfurating them under hydrothermal condition. The achieved hybrid ZnS/ZnO PHSs are about 1–1.5 µm in diameter, whose shell is assembled by secondary nanoparticles with the size of 40–70 nm. The results of gas sensing tests indicated that after modification with ZnS-ZnO heterojunctions, the gas sensing performances of the ZnO PHS sensor to triethylamine (TEA) were remarkably improved, especially in terms of faster response speed (4 s for 100 ppm TEA), higher sensitivity (0.520/ppm for 1–30 ppm TEA) and better selectivity (STEA/acetone = 8.8). The ZnS-ZnO heterojunction-related sensitization mechanism was discussed in detail.