Preparation And Its Property Of Zinc Oxide With Multi-Structure Assisted By Ionic Liquids-Co-Alanine

It is well known that inorganic micro/nanomaterials, due to their unique structures and outstanding physicochemical properties, have been applied in materials, biology, medicine, microelectronics, and micromachines. Zinc oxide as a versatile smart member, has been attracting extensive attention, owing to its wide range of technological applications including field emitters, sensors, transparent conductors, catalysis, and water-clarifier agents. And, above all, it is attribute to excellent performances of ZnO which possesses a direct wide band gap (3.37eV) and a large exciton binding energy (60 meV) at room temperature. Many efforts have been devoted to manipulating the shape and size of various ZnO materials on the principle that material properties strongly depend on its structure. Generally speaking, these methods have some limitations and demerits such as toxicity, volatility, high costs, long reaction time, non-uniform samples size and so on. In this context, it is important to find a green methodology with simple and effective.Ionic liquids show great advantages while applying to the synthesis of inorganic micro-nanometer materials, because of their merits:innocuity, high thermal stability, non-volatile, wide liquid range and outstanding designability. It is worth pointing out that ionic liquids has developed to a focal point of interest in both academia and industry. Nowadays ILs have been familiar to lots of reaschers and employed to prepare different morphologies of ZnO micro/nanoparticles. In spite of good progress on ZnO fabrication, it is still a challenging proposition to make the reaction system more economic and simpler. Therefore, we planed the synthesis system with ionic liquid-alanine solution and efficient preparation process without harmful organic solvents to get first products and second products successively. Besides, two or three kinds of mixed zinc salts were separately used for preparing zinc oxide with different morphologies. Fourier Transform interferometer (IR), scanning electron microscope (SEM), X-ray powder diffraction (XRD), UV-vis absorption spectroscopy and photo luminescence emission spectroscopy (PL) were applied to characterize the compositions, morphologies and optical properties of the products.In this dissertation, we first synthesized three kinds of ionic liquids ([BMIM]Cl, [BMIM]Br, [BMIM]OH) and used them to prepare ZnO crystals.(1) Diabolo-like ZnO was successfully synthesized in ionic liquid ([BMIM]Cl)-alanine solution by hydrothermal method at 160℃, using combinations of zinc salts including zinc sulfate, zinc acetate and zinc chloride. The effects of the various factors on crystal morphologies were studied, containing zinc sources, tempertatures, and ionic liquids. The results showed that anions influenced space structures of samples, while ionic liquid and temperture played a role of driving force. UV spectra showed that the peaks of diabolo-like ZnO and scale-like ZnO synthsised at 120℃ remained the same in the position and varied in the strength. As it is clearly for diabolo-like ZnO, the absorption intensity enhanced and was possible influenced by its stereochemical structure.(2) The precursor solution containing Zn2+ was successfully synthesized in ionic liquid ([BMIM]Br)-alanine solution by hydrothermal method at 150℃, using combinations of zinc salts including zinc acetate and zinc chloride. Then NaOH was added to the solution at room temperature accompanied by generation of white precipitate which was ZnO multilevel-structure assembled by nanoparticles. The effects of the various factors on crystal morphologies were studied. And the results showed that zinc saults, temperature, ionic liquid, and alanine had a great influence on the mophology of ZnO. UV and PL spectra showed that self-assembled nanoparticles ZnO had typical properties of absorption and luminescence. The photocatalytic activity of the samples was evaluated by the photocatalytic decomposition of methyl orange, and typical self-assembled nanoparticles ZnO displayed best activity.(3) The precursor solution containing Zn2+ was successfully synthesized in ionic liquid ([BMIM]Cl)-alanine solution by hydrothermal method at 160℃, using combinations of zinc salts (ZnCl2, Zn(CH3COO2)2, ZnSO4,). Then NaOH was added to the solution at room temperature accompanied by generation of white precipitate which was ZnO hierarchical structure assembled by nanoflakes. ZnO with different frameworks and morphologies can be prepared by controuling experimental conditions and confirmed by comparative experiments. The photocatalytic performance of the samples was investigated using the degradation of the methyl orange and rhodamine B under the irradiation of ultraviolet radiation. The results revealed that the morphologies of samples had biggish influence on their photocatalytic properties.