Enhancement of Acetone Gas-Sensing Responses of Tapered WO(3) Nanorods through Sputtering Coating with a Thin SnO(2) Coverage Layer

WO(3)–SnO(2) composite nanorods were synthesized by combining hydrothermal growth of tapered tungsten trioxide (WO(3)) nanorods and sputter deposition of thin SnO(2) layers. Crystalline SnO(2) coverage layers with thicknesses in the range of 13–34 nm were sputter coated onto WO(3) nanorods by controlling the sputtering duration of the SnO(2). The X-ray diffraction (XRD) analysis results demonstrated that crystalline hexagonal WO(3)–tetragonal SnO(2) composite nanorods were formed. The microstructural analysis revealed that the SnO(2) coverage layers were in a polycrystalline feature. The elemental distribution analysis revealed that the SnO(2) thin layers homogeneously covered the surfaces of the hexagonally structured WO(3) nanorods. The WO(3)–SnO(2) composite nanorods with the thinnest SnO(2) coverage layer showed superior gas-sensing response to 100–1000 ppm acetone vapor compared to other composite nanorods investigated in this study. The substantially improved gas-sensing responses to acetone vapor of the hexagonally structured WO(3) nanorods coated with the SnO(2) coverage layers are discussed in relation to the thickness of SnO(2) coverage layers and the core–shell configuration of the WO(3)–SnO(2) composite nanorods.