Study On Preparation, Modification And Properties Of Zinc Oxide Nano-Arrays

The development of new kinds of energy and the management of the environment are main measures to solve the problem of energy shortage and environment deterioration, while the high cost and low efficiency are still the main problems of those two means. Therefore, it is of great significance to explore new preparation process and cheap materials to develop the new kinds of energy and effectively govern environment pollution. In this thesis, we prepared ZnO nano-arrays and its composites by hydrotherm, chemical bath deposition and photochemical deposition which are low-cost preparation methods. The main results and achievements are as follows:(1) ZnO nano-arrays were deposited on the FTO glass substrates by hydro thermal method. The zinc acetate was used as zinc source, HMTA as the OH-source and PEI as the additive, the influence on the properties of the ZnO nano-arrays under different preparation conditions were studied. The results showed that the height and diameter of ZnO nano-arrays decreased with the increasing of the solution concentration of seed layer while the regularity of ZnO nano-arrays showed increased. As the molar ratios of Zn2+ to HMTA increased, the lengths of ZnO nano-arrays decreased while the diameter firstly increased and then decreased. When the molar ratios of Zn2+ to HMTA is 5:5, the optical band gap is 3.2 eV which is more close to the theoretical value at the room temperature. With the concentration of precursors increased, both the length and diameter of the nano-arrays were increased. In addition, when the precursors concentration was 50 or 75 mM, the shape of ZnO nano-arrays transformed from the hexagonal rod like to conical needle like. Both the length and diameter of ZnO nano-arrays were increased with the increasing of the temperature while defects of ZnO nano-arrays showed an increase. In conclusion, the samples prepared under molar ratio of Zn2+ to HMTA of 5:5, the concentration of precursors of 25 mM and the temperature of 90 ℃ has relative high crystallinity and regularity.(2) Spike-shaped CuO/ZnO heterostructure were deposited on the surface of ZnO nano-arrays by chemical bath deposition method. The copper nitrate was used as the copper source, with potassium sodium tartrate tetrahydrate (PSTT) as a complexing agent, sodium hydroxide and sodium carbonate as an alkaline medium, and formaldehyde as a reducing agent, the influence on the properties of the spike-shaped CuO/ZnO nano-arrays heterostructure under different preparation conditions was studied. The results showed that when the PSTT concentrations increased, the quantity and diameter of the CuO nanoparticles on the surface of ZnO nanoparticle arrays was increased, transmission of composite-arrays was also increased; while the volume of formaldehyde increased, the quantity and diameter of CuO nanoparticles was decreased. Moreover, we found that the covered CuO nanoparticles samples prepared under 2.6 mM PSTT and 0.125% v/v formaldehyde exhibited bigger improved photocatalytic property than pure ZnO nano-arrays under UV irradiation, the degradation rate for methyl orange can reach to 92.8%. And the absorption edge of composite-arrayes is extend from 380 to 560 nm at the UV-visible region(3) Flower-like CuO/ZnO nano-arrays heterostructure were deposited on the tip of ZnO nano-arrays by photochemical deposition method. The copper nitrate was used as the copper source with distilled water as the solvent, the effect on the properties of the flower-like CuO/ZnO nano-arrays heterostructure under different preparation conditions was studied. The results showed when the UV light intensity increased from 15 to 90 W, the covered CuO nanoparticles clusters transformed the cotton wool shape to spike shape, the absorbance of CuO/ZnO nano-arrays heterostructure was increased with the increasing of UV light intensity while the number of defects were reduced. When the copper source concentrations were increased, CuO nanoparticles clusters on the tip of ZnO nano-arrays were grown bigger, absorbance of composite arrays was reduced. The samples prepared under copper source of 3 mM and UV light intensity of 60 W showed the best degradation of MO.