Structure-dependent gas detection ability of clustered ZnS crystallites with heterostructure and tube-like architecture

ZnS crystallites with a core-shell heterostructure (ZnO-ZnS core-shell rods) and tube-like architecture were synthesized through a facile chemical solution route. Many tiny ZnS particles were clustered and compacted to form the shell layer of the ZnO-ZnS core-shell rods and the wall of the ZnS tubes during sulfidation of vertically aligned ZnO rods. X-ray diffraction and transmittance electron microscopy images revealed that the ZnS shell layer of the ZnO-ZnS core-shell rods and the wall of the tubes were polycrystalline, and that many domains or grain boundaries were present in the ZnS layers. The sensitivities of ZnO-ZnS core-shell rods and ZnS tubes to reducing and oxidizing gases differed. The ZnO-ZnS core-shell rods were more sensitive to reducing gases, whereas the ZnS tubes were more sensitive to oxidizing gases. The different gas sensing properties of the ZnS-based heterostructures and tubes are further discussed in relation to their microstructures. The heterojunction at the ZnO/ZnS interfacial region resulted in the differing gas sensing properties of the ZnS-based heterostructures and tubes in this study.