Morphology Controlled Synthesis Of Some Metallic Oxides And Hollow Nanostructures

Many kinds of nanometer materials are important basis of nanoscience and nano- technology. One of the processes of making nanoscience practical is how to fabricate nanometer materials with particular sizes and morphologies. On the other hand, hollow nanometer materials arouse infinite interests of many researchers in recent years. The hollow nanostructures and their novel properties bring a bright future of application in many fields such as catalysis, medicine, photoelectricity and so on. In this dissertation, morphology controlled synthesis of some metal oxides were studied firstly. Then we prepared hollow nanostructures by Kirkendall effect using the metal oxides nanostructures as precursors.Morphology controlled synthesis of Cu₂O nanoparticles were studied in the 2^nd chapter. Cu₂O nanoparticles were prepared at room temperature with vitamin C as reducing agent and some salts as the origin of Cu. The kinds and and concentrations of stabilizing agents influence the morphologies and sizes of Cu₂O nanoparticles. Square, global and polygonal Cu₂O nanoparticles were prepared. We discussed the concrete reasons in terms of the theory of crystal growth in aqueous solution. In addition, different Cu salts have obvious effects on the morphologies. In this chapter, optical properties of UV-vis absorption of different Cu₂O nanoparticles were also studied.Preparation of ZnO nanostructure with different morphologies and sizes was studied in the 3nd chapter. Micrometer particles, nanometer particles and nanorods of ZnO were prepared by hydro-thermal method. pH values and temperatures decide the morphologies and sizes of ZnO nanostructure. We tried to probe into the intrinsic factors of the crystal growth in terms of theory of nucleus formation at low limited codditions.Morphology controlled synthesis of CuO and CdO nanostructures were studied in the 4th chapter. We prepared some different nanostructures by hydrothermal method, burning and thermal decomposition in aqueous solution. Furthermore, we discussed primarily the influencing factors combining with theory of microcosmic material formation.In the last three chapters of this dissertation, morphology controlled synthesis of hollow nanostructures were studied. In existing literature, the general hollow structures are hollow spheres and the familiar methods must recur to templates such as cabon spheres and macromolecule spheres. We prepared systemly the hollow nanostructures of some sulfides with different morphologies by Kirkendall effect using oxides nanostructures as precursors. Furthermore, we studied detailedly the specific reaction conditions and mechanism.Square and global Cu₇S₄ hollow nanometer particles were prepared using Cu₂O as precursors. The hollow degree of final products was decided by the mole ratio between precursor and Na₂S. Complete hollow nanometer particles could not be obtained below the ratio 1 to 3. There were two distinct characterictics: (1) The morphologies of precursor and hollow product are very similar. (2) The reaction proceeds from surface to inner part of precursor nanoparticles impelled by the diffusion of S^2- ions. Ag₂S hollow nanometer spheres were also acquried with Ag₂O nanometer particles as precursor.Hollow nanostructures of ZnS were prepared using ZnO nanostructures as precursors. At room temperature, ZnO and Na₂S could not react, which is different from the reaction between Cu₂O and Na₂S. When temperature was rised to 80℃or above, the reaction processed gradually and hollow nanostructures could be observed on TEM. We studied chiefly the impacts of reaction temperatures and times on hollow degree and tried to find the best conditions. On the other hand, the sizes of precursors have obvious effect on the results of hollow structures. And concrete machanism of Kirkendall effect was studied in hydrothermal environment. Finally, the optical properties of nanoparticles with different compositions were tested and the corresponding determinants were discussed.In the final chapter, CuO and CdO nanoparticles were used as precursous to prepare hollow nanostructures according to the same principle and method. And the hollow nanoparticles of CdS was prepared successfully. We tried to find the universality of the sulfurization reactions between metal oxides and Na₂S solution. Furthermore, we roughly calculated the bond energies of some metal oxides using thermodynamic data to interpret the different degrees of diffculty of the sulfurization of different matal oxides.