Preparation And Photocatalytic Properties Of Nano-zinc Oxide

Nanometer zinc oxide(ZnO)is an importantⅡ-Ⅵwide band gap (Eg=3.37eV) semiconductor with a relatively high exciton binding energy of 60 meV. Nano-ZnO has special properties and application in the field of magnetism, sensitivity, antibiosis and antipoisoning, ultraviolet ray shield, etc which the common ZnO has not. But in practice,Its strong polarity and easy aggregation limit its excellent function. So, preparation and surface modification of ZnO nanoparticles is hotspot in nanometer science. At the same time, different precursors with different properties can be made by different raw materials.The kinds and properties of precursors influence the properties of nano-ZnO greatly. This paper based on analyzing the preparation of nano-ZnO and the problems of application, investigated the preparation methods of nano-ZnO, and then preliminary studied the reaction mechanism on photocatalysis, has a great significance for further development and application of this photocatalyst.The paper is composed of the following four parts:In the first part, nanoparticles were prepared by the microwave method using the zinc acetate (Zn(CH₃COO)₂.2H₂O) and hydrogen peroxide (H₂O₂) as the starting materials for the first time. It is shown that during the ZnO₂ decomposition into ZnO at sintering temperature higher than 200℃, the by-product in the preparation process is O₂, The ZnO and ZnO₂ powders prepared by this method are with crystal structure and high purity. This green technology without any pollution is simple, low energy consumption. various measuring methods were used to characterize ZnO nanoparticles, such as diffevential scanning calovimltry(DSC),powder X-ray diffraction(XRD),fourier transform infrared(FT-IR) spectorscopy, transmission electron microscopy(TEM), specific surface areas(BET) and high resolution transmission electron microscopy(HRTEM). Seeond , preparation of nano zinc oxide by microwave method. The thesis for the first time take the zinc acetate (Zn(CH₃COO)₂.2H₂O ) and the urea (CO(NH₂)₂) as raw material, different surfactants have different influence on the size of ZnO in the process of preparation of nano-ZnO by the microwave precipitation method . Various measuring methods were used to characterize ZnO nanoparticles,such as DSC ,XRD,FT-IR, SEM,BET and HRTEM . The experiments showed that, compound surfactants and anion surfactants were better than non-ion surfactant for nanoparticle ZnO preparation by microwave method.In the seeond part, preparation of nano zinc oxide by the sovlothermal method. Take the zinc acetate (Zn(CH₃COO)₂.2H₂O) as raw material, the methanol and N,N-dimethylformamide (DMF) are the solvents, through changes the solvent preparation nanometer zinc oxide with the sovlothermal method. ZnO nanoparticles were synthesized in a simple solution route without assistance of base, surfactant, template etc., by a single-step process. with test technologies and so on the XRD, FT-IR, SEM,BET and HRTEM carries on the characterization to the product structure and the superficial appearance, the results indicate that the product appearance in which with the sovlothermal method changes along with the solvent change, when methanol was partly replaced by DMF, product by particle cluster to sphere pellet transformation.In the third part, hydrolysis method for growing nano-ZnO. Take the sodium tartrate anhydrous, the zinc acetate(Zn(CH₃COO)₂.2H₂O)and the ammonia as raw material, through the change a reaction temperature, synthesize ZnO via hydrothermal thermolysis of tartaric acid-deived complex precursor with test technologies and so on the DSC ,XRD, FT-IR,TEM,BET and HRTEM carries on the characterization to the product structure and the superficial appearance, the results indicate the appearance results in which changes along with the temperature change, when the temperature elevates gradually, product by the diamond to sphere pellet transformation.In the four part, to understand the relationship between the structure and photocataiytic property of ZnO nanocrystals, the photocataiytic activity of the as-synthesized samples has been investigated by choosing the degradation of Methyl orange ,Methylene blue , Rhodamine B and Congo red. The results show that the ZnO nanoparticles is a good photocataiytic property , and the surface characteristics of ZnO including size, shape and surface composition will influence the photocataiytic process greatly.