ZnO Synthesized Via Hydrothermal Method And Their Photoluminescence Properties

Along with the development of information technology, novel nanomaterials are being increasingly demanded and the requirements on their properties are become stricter. At present, the controlled synthesis of nanomaterials with different morphologies has always been a focus for chemists and material scientists. Moreover, further research on the physical and chemical properties of nanomaterials is as important as synthesis. As one of the widely utilized fluorescent n-type semiconductor oxide, zinc oxide has a wide bandgap energy (3.37ev) and a large exciton binding energy (60mev). Due to its favourable structural, optical and catalytic properties, zinc oxide has been widely used as gas sensors, antireflective coatings, photocatalyst, field-emission device and in solar cells. In this thesis, research on the preparation of hierarchically structured zinic oxide, synthesis via hydrothermal method at low temperature. The main content and some results are as follows:1)In this paper, a simple hydrothermal method is reported to synthesize ZnO crystals with zinc nitrate and hexamethylenetetranmine. Soluble salts such as NaCl, NaF, KCl, C6H5Na3O7, Na2SO4, K2SO4, NiNO3, Na2CH3COOH and Na2CO3 were used to tune the morphology of ZnO. It is demonstrated that the morphology of the final products can simply be tuned by adding different amounts of soluble salt. ZnO microparticles were prepared without any soluble saltadding and in the same time, ZnO microspheres and nanoflowers were selectively prepared in the presence of different amounts of NaF; ZnO nanosheets were obtained after adding an appropriate amount of NaCl, Na2SO4, or K2SO4; ZnO nanobelts were obtained in the presence of appropriate amount of sodium citrate (C6H5Na3O7).2) The structures of the products were characterized by X-ray powder diffraction (Rigaku RINT2400 with Cu K_ radiation). All diffraction peaks can be indexed as the hexagonal phase of ZnO, which are in good agreement with the JCPDS, No.65-3411.3) The images of samples were obtained with scaning electron microscopy. Analysis of images shows that soluble salts play an important role in the growth of ZnO crystals.4) The hierarchical structures of the products were characterized with laser Raman spectrometer. Raman peaks of ZnO products, which were obtained in the presence of different sorts of soluble salt, are much different. This indicates that the crystal growth of ZnO can be affected by soluble salts.5) The photoluminescence (PL) properties of these products were analysized, and the origin of the PL was discussed.