| Based on the investigation of a great of related literature, the author has made a brief review concerning the structure, properties, applications, synthetic methods and expectation of nanocrystalline materials. The aim of work is focused on developing synthesis of inorganic functional materials. By facile hydrothermal or solvothermal routes, we had synthesized some special novel nanostructures such as a-MnS spheres,flower-like ZnO nano-film,ZnxCd1-xS hierarchical architectures. What's more, properties of the as-synthesized samples and growth mechanism in the hydrothermal or solvothermal synthesis were also studied as the emphasis. The main results are summarized as follows:1. Two-step Solvothermal Synthesis of a-MnS spheres: Growth Mechanism and CharacterizationStable a-MnS spheres have been successfully synthesized by two-step solvothermal method and traditional solvothermal technique without any surfactant assistance. The XRD patterns and FE-SEM images show that the as-prepared samples are cubic a-MnS micro-spheres with different morphologies. The formation of spheres was studied under different experimental conditions. The two-step solvothermal method helps us cognize the growth mechanism in the solvothermal synthesis better. The result shows that template-direct growth and Ostwald ripening for the formation of the a-MnS spheres are approved. In addition, both mechanisms can be effective at the same time. The UV-Vis absorption spectra reveal that the samples synthesized by different methods have the absorption location at the same wavelength (around 365 nm), but the maximal absorption value was different.2. Liquid phase epitaxial growth and optical property of flower-like ZnO nano-film on Zinc foilLarge scale flower-like ZnO nano-film has been synthesized on Zinc foil by a simple hydrothermal method. Their morphology and microstructures were characterized and analyzed by X-ray spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The results show the flower-like ZnO nano-film is composed of nanosheets which are hexagonal phase single crystal with 200-300 nm in width, 50 nm in thickness. The formation of flower-like ZnO nanosheets on the Zn foil can be explained by the liquid phase epitaxial growth mechanism by changing the reaction condition (time, temperature and PH value), in which ZnO humps formed by H2O2-assisted hydrothermal oxidation of Zn foil act as the buffer. This H2O2-assisted hydrothermal route can be expanded to synthesis other oxides, such as TiO2, CdO. The photoluminescence spectrum of the sample exhibits only a sharp and strong UV emission centered at 386nm.3. Mix-solvothermal synthesis and optical properties of ZnxCd1-xS complicated hierarchical architecturesA solvothermal method using the mixed solvents was developed to prepare ZnxCd1- xS hierarchical architectures. Used Zn (CH3COO)2·2H2O and 3CdSO4·8H2O and (NH4)2S as the reactant sources, the reactions were maintained in the mixed of diethylenetriamine and water. The result shows the morphology and properties of the specimen have been controlled or adjusted only by changing the cation molar ration of Zn/ Cd in the reactants. With the increase of the Zn content, XRD patterns shows regular variation and the parameters (a, c) decreased linearly, which is consistent with Vegard' law. XPS analysis also confirms the existence of ZnxCd1-xS nanocrystals. Their morphology and microstructures were characterized by FE-SEM and HRTEM. Morphologies of the samples were gradual changing with a decrease of Zn content from the sphere-like structure made of fine rods to the tree-like nanostructure with many arms. The PL spectra of the series ZnxCd1-xS nanocrystals have been revealed, from which we can find optical properties variation of the samples. In addition, the mechanism of reaction and the selection of the reagents have also been investigated.
|
PDF Full Text Request