Functionalization of ZnO nanorods by CuO nanospikes for gas sensor applications

This study reports the functionalization of ZnO nanorods (NRs) through spike-shaped CuO nanoparticles (NPs) to create a nanosized p-n junction, their structural properties, and the mechanism by which bundles of these NRs are able to sense CO gas. The CuO NPs were deposited on solvothermally grown ZnO NRs by a chemical bath deposition method. The formation of the highly crystalline heterogeneous nanostructure of the ZnO NRs was confirmed by electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The effect of the p-n junction on CO sensing behavior of ZnO NRs was evaluated in dry air. The response of ZnO NRs sensors to CO was enhanced after loading with CuO NPs. The role of catalyst NPs is explained by both a collective- and a local-site approach, in which deposition of catalyst NPs changed the overall band structure and surface chemistry of the ZnO matrix.