CuO/ZnO Heterostructured Nanorods: Photochemical Synthesis and the Mechanism of H2S Gas Sensing

This study reports on the structural properties of CuO/ZnO nanorods and the mechanism by which bundles of these nanorods are able to sense H2S gas. The CuO/ZnO nanorods were prepared by deposition of CuO nanostructures on the hydrothermally grown ZnO nanorods using a photochemical method. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm that the heterogeneous nanostructure of the CuO/ZnO nanorods was highly crystalline. The H2S gas sensing properties of CuO/ZnO nanorod bundles was evaluated in air containing dilute H2S gas at sensing temperatures (T-s) <= 500 degrees C. The response of CuO/ZnO nanorod sensors to H2S gas was enhanced compared to that of bare ZnO nanorods. The heterostructured nanorods showed an exponential increase in sensing tendency with T-s. X-ray photoelectron spectroscopy analysis results indicated that the enhanced response of CuO/ZnO nanorod sensors is due to the chemical conversion of CuO into CuS upon H2S exposure, which acts as an electrical gate in the CuO/ZnO sensor.