TiO2-ZnS core-shell composite nanorods were synthesized by using ZnO as a sacrificial shell layer in a hydrothermal reaction. ZnO thin films of different thicknesses were sputter-deposited onto the surfaces of TiO2 nanorods as templates for hydrothermally synthesizing TiO2-ZnS core-shell nanorods. Structural analysis revealed that crystalline TiO2-ZnS composite nanorods were formed without any residual ZnO phase after hydrothermal sulfidation in the composite nanorods. The thickness of the ZnO sacrificial shell layer affected the surface morphology and sulfur-related surface defect density in hydrothermally grown ZnS crystallites of TiO2-ZnS composite nanorods. Due to the distinctive core-shell heterostructure and the heterojunction between the TiO2 core and the ZnS shell, TiO2-ZnS core-shell nanorods exhibited ethanol gas-sensing performance superior to that of pristine TiO2 nanorods. An optimal ZnO sacrificial shell layer thickness of approximately 60 nm was found to enable the synthesis of TiO2-ZnS composite nanorods with satisfactory gas-sensing performance through sulfidation. The results demonstrated that hydrothermally derived TiO2-ZnS core-shell composite nanorods with a sputter-deposited ZnO sacrificial shell layer are promising for applications in gas sensors.
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