Preparation And Characterization Of ZnO Nanoparticles By Oxidation Of Metallic Zinc In H₂O₂ Solution

ZnO nanoparticle is an important oxide semiconductor material, which is of potential applications in many areas. In this paper, we invented a novel method to prepare ZnO nanoparticles. The crystalline structure, optical and electrical properties of the nanoparticles were characterized, and some of the applications were investigated.Untill now, various techniques have been employed to prepare ZnO nanoparticles, however these methods are usually complex and costly in order to control the particle size, the size uniformity, and the purity, which are very important for optical and electrical device applications. So, it is necessary to find a new method to synthesize ZnO nanoparticles with the following properties: high purity, size controllability, size uniformity, low cost and mass production. In this paper, a novel method for fabricating ZnO nanoparticles was described: Firstly, zinc (Zn) was oxidized in hydrogen peroxide (H₂O₂) solution to form Zn(0H)2 sol;secondly, the sol was sprayed and annealed to form ZnO nanoparticles. Since no precipitation reagent was added, the purity of ZnO nanoparticles prepared by this method is super to that of ZnO nanoparticles prepared by other liquid chemical method.The as prepared ZnO nanoparticles were characterized systematically. The particle size was investigated by X-ray diffraction (XRD). The influence parameters on the particle size, including: oxidation reaction temperature, reaction time, H₂O₂ concentration, solution PH value and processing temperature were investigated by XRD. It is found that the processing temperature has great influence on the particle size. The particle size of ZnO nanoparticles is in the range of 5-25 nm for annealing temperature from 200 ℃ to 600 ℃. By controlling the annealing temperature , the particle size can be easily controlled. The atomic bonding characters oin the nano-particles were investigated by FTIR and Raman spectrum, The El mode frequency shows blue-shift, while the E2 mode frequency shows red-shift as the particle size decreases. These resultsshow that there exists the stress in the nano-crystalline ZnO.particles.The microstructure of ZnO nanoparticles was investigated by AFM, SEM and SAXS. Both AFM and SEM results show that nano-ZnO was spheric shaped, and the results of SAXS show that the particles have no sharp interface and the fractal dimensionality is 1.9.The research has been focusing on nano ZnO due to its excellent optical and electrical properties and its prospects in optoelectricals applications. On the basis of the successful preparation of nano ZnO particles with high purity and size controllability, the optical properties, the electrical properties, and gas sensitivity of ZnO nanoparticles were characterized. The optical properties of ZnO nanoparticles were studied by UV-vis absorption and photoluminescence (PL). The optical energy bandgap show typical blue-shift as the partcile size decreases, which is attributed to the quantum effect, but the ultraviolet PL peaks show red shift compared with the optical energy bandgap of the bulk ZnO, which is attributed to the acceptor-exciton complex.At last, we investigated the applications of ZnO nanoparticles. Firstly, we prepared nano-ZnO embed SiO2 glass. The photoluminescence of the nano ZnO embed S1O2 glass and the influence parameters were investigated. Secondly, the mesoporous S1O2 glass was obtained by treating the nano ZnO embedded SiO2 glass in HC1 solution. Thirdly, conductive Al-doped ZnO nanoparticles were prepared, and the measurement of the resistivity of nano-ZnO was discussed. Then, ZnO nanoparticle film based photodetector and photoconductance were investigated. The results show that the nanoparticles with larger particle size has high responsivity. Finally, ZnO nanoparticle films made gas sensor was demonstarted, which can work at room temperature without a heater.