Preparation And Properties Of ZnO Nanostructure By Electrochemical Anodization Method

This dissertation focused on preparing the ZnO nanostructures by using electrochemical anodic oxidation in two different electrolytes. By adjusting the electrolyte concentration, reaction time and reaction voltage we obtain diverse ZnO nanostructures films. The growth mechanism of these structures is analysed, and the PL and Raman spectra are studied. Finally, we study the electrowetting behaviour of ZnO nanostructure films.At First, we give a brief introduction to the concept, history and application field of nanotechnology. Then we present some conventional synthesis approaches for nanostructures and their basic principles. According to the growth environment, they can be mainly divided into two categories: vapor phase method and liquid (solution) phase method. Afterthis,main apparatus used for characterizing nanostructured materials are introduced, such as transmission electron microscope, scanning electron microscope, X-ray diffraction system, atomic force microscope, and photoluminescence (PL) spectra.Second, we reviews the research background of nanoZnO materials and some of the special structure of nanoZnO (including nanorods, nanowires, nanocomb, nano saws, nano spring and nano ring, etc.). We finally expounded some applications of nanoZnO in industrial .Third, we compare three different kinds of preparation methods (Chemical Vapor Deposition, Aqueous method and electrochemical method). Then we introduce how to prepare ZnO nanostructures films by electrochemical anodic oxidation. Next, we describe some basic parameters and optical properties of nanoZnO. Finally, we prepare ZnO nanostructures by using a simple and rapid electrochemical anodic oxidation method in two different electrolytes(acid environment and alkali environment). We can obtain ZnO thin films with diverse nanostructures, including nanodot, nanowire and nanoflower by adjusting the electrolyte concentration, reaction time and reaction voltage. We deeply study and analyse the intrinsic growth mechanism and character the optical properties of ZnO films. These ZnO films have the similar Raman spectrum. Here a very strong visible emission and narrow full-width of half-maximum (FWHM) (30-40nm) has been observed in PL spectrum.We can infer: 1. The zinc interstitial defect is main defect in ZnO films; 2.The ZnO thin films reveal very strong visible emission that is ascribed to the transition between VOZni and valence band. This ZnO films may have potential applications in visible optoelectronic devices, photoanodes of dye-sensitized solar cells and sensors because of their strong visible emission.Finally, we study the electrowetting behaviour of ZnO films. The electroinduced surface wettability conversion from the superhydrophobic to hydrophilic state was observed by adjusting the applied voltage between the Pt wire and ZnO films. And the generation of surface defective sites on ZnO films under electric field was used to explain the transition mechanism. We demonstrate that the surface wettability can also be governed by the application of external potential on the ZnO nanostructure films, which is ascribed to the generation of surface defective sites on ZnO films under effect of electric field.