Preparation And Gas Sensing Properties Of ZnO-based Nano-materials

The brief gas responsive principles are based on chemisorptive and redox reactions on the surface of the sensitive meterials. Therefore, the gas sensing performances would be improved by the treatments on microstructure, morphology and surface of sensitive meterials. Bare ZnO nanorods were prepared by the method of chemical bath deposition. In order to improve the properties of the gas sensors based on ZnO, various material-modified treatments were employed on the bare ZnO nanorods.This paper mainly includes the following contents:1. ZnO nanorods were prepared by the method of chemical bath deposition. The morphology of ZnO nanorods were modulated with different ZnO seed layers which were prepared by spray pyrolysis and Czochralski method. The result of SEM images showed that the samples nucleated on seed layer preparated by spray pyrolysis are grown up with flower structure and the samples grown on the Czochralski method seed layer are smooth surface, and no phenomenon of reunion.2. The gas sensing properties of chemical- resistance type gas sensor is significantly affected by surface adsorption and chemical reaction. ZnO nanorods with hexagonal wurtzite structure were synthesized by the facile chemical bath deposition method. In order to alter their gas response towards the various test gases, the surfaces of ZnO nanorods were decorated with different nanoparticles, such as Ag and NiO. XRD test results found that the diffraction peak of surface modifiers on ZnO nanorods was not detected. However, the tiny modifiers were found in the figure of SEM. The gas sensitive detection results show that the gas selectivity and sensitivity to ethanol of surface modification of ZnO nanorods have the very big enhancement.3. Two different morphologies of ZnO and CuO composite nanometer heterostructure were prepared by two methods respectively. The first method, CuO nanoparticles were prepared by the same method with the fabrication of ZnO nanorod. Results show that the SEM images of ZnO nanorods CuO nanoparticles appear tiny flower structure. The gas sensitive detection results show that the improved selectivity and sensitivity of H2 S gas. The second method, the copper powder was oxidated, then the ZnO nanoparticles deposited on the surface of the sample by photochemical deposition method. The gas sensitive detection results show that the improved sensitivity of ethanol gas.4. Iron oxide was prepared on the surface of ZnO nanorods by hydrothermal method,then ZnO-FexOy composite nanomaterials heterostructure was fabricated by this method. Gas sensitive test results show that the composite nano materials improved sensitivity to ethanol gas.