Synthesis And Properties Of Copper Oxide (CuO) Nanostructures And Its Composite

CuO nanostructures as well as CuO/ZnO composites have potential applications in photo-detection and photochemistry, catalysis, and sensors. Such applications require the size and shape well-defined of CuO nanostructures. Up to date, however, control over size and shape as well surface structures of CuO nanostructures has still not met this requirement. Here, we synthesized CuO nanostructures and its hierarchitectures by using microwave-assisted hydrothermal method in the presence/absence of surfactants. We also prepared CuO/ZnO composites by chemical precipitation. Furthermore, we investigated the optical and catalytic properties of these as-synthesized products. The gas sensing performance of CuO nanostructures with different shapes was investigated. It was found that the gas response of the CuO based sensor depends on its shape.CuO nanostructures with size and shape controlled have been synthesized by a two-step method involving chemical precipitation (CP) and subsequent microwave-assisted hydrothermal (MH) processes. The samples were characterized by XRD, TEM, SEM, UV-vis, and FTIR. The results from XRD patterns show that all samples are monoclinic pure phase of CuO. TEM and SEM images exhibit rod-, leaf-, belt-, sheet-, and dendrite-like CuO nanostructures, respectively. UV-vis spectra indicate that the optical absorption property of the samples would be strongly dependent on their size and shape. Formation of CuO nanostructures was studied by varying the concentration and the type of the surfactants, the concentration of the starting copper salt, the temperature and the manner of the CP process, and the reaction time of the MH. Small sized CuO nanostructures could be obtained easier by arising the CP temperature than relative low one. Also, small molecules affected the size and shape of the samples obtained, for example the addition of sodium citrate in the reaction system suppressed anisotropic growth of CuO, resulting in spherical nanoparticles. CuO with different shapes for the catalysis of thermal-decomposition of AP showed shape-dependent catalytic activity. The high temperature of decomposition of AP was lowed by 103.6, 122.5, 113.8, 99.1 oC.Secondly, CuO hierarchical structures with different shapes such as flower- and urchin-like, have been successfully prepared by using the microwave-assisted process using the complex of Cu(OH)₄^2- as the precursor in the presence of surfactants. Flower-like architectures are radically assembled by using both of two CuO nanostructures—nanorods and nanoplates—as building blocks. Urchin-like CuO hierarchitechtures consisting of radically aligned nanotubes were synthesized with the co-assistance of PEG-400 and citric acid. It was found that synthetic parameters such as the concentration of NaOH, the amount of PEG-400 and/or citric acid affected the final shape and surface structure of the hierarchitechtures. The shape transition from flower-like to urchin-like took place by both increasing the concentration of NaOH and PEG-400, and the surface structure could be tailored by controlling over the amount of citric acid.Thirdly, CuO/ZnO nano-composites have been prepared by adopting a chemical precipitation using Zn(OH)₄^2- as the precipitator. The size and shape of CuO/ZnO nano-composites was strongly dependent on the precipitation temperature. It was found that the as-synthesized composites showed high catalytic activity for the thermal decomposition of AP. The decomposition temperature of AP was lowered by 156.7, 161.3, 157.1, 158.9 oC. The gas sensing behavior of the composites was similar to that of p-type semiconductors such as CuO.