| Low-dimensional hierarchical and heterogenous nanostructure material is one of the research focuses of materials science currently because of its special function in optics, electricity and magnetic. ZnO is a novel II-VI semiconductor material. The energy gap of nano-ZnO get wider due to the quantum size effect (conduction band potential get more negative and valence band potential get more positive), so a stronger oxidation-reduction capacity has gain that greatly improving the catalytic activity. A lot of researchers have devoted in developing ZnO in the visible light thanks to it's greater than the TiO2 band gap. SnO2-based lithium-ion battery anode material has emerged in the battery fields due to its high initial theory capacity. The mesoporous carbon polyhedron material in close-packed model has a variety of advantages, it will enable different applications undergo major changes, such as gas separation, water purification, catalytic and electrochemical applications of the electrode materials.In this thesis, various low-dimensional morphologies of novel hierarchical and heterogenous nanostructure materials have been fabricated mainly via hydrothermal process. Such as Dandelion-like Ga-doped ZnO/stearic acid nanocompounds, SnO2@carbon core-shell nanochains and the close packing mesoporous carbon polyhedron materials. The crystalline, morphologies and structure of samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Meanwhile the stuctrues and characters of the as-obtained products were investigated on fluorescence spectra (PL), Fourier transform infrared spectroscopy (FTIR) and Raman spectra. The posssible mechanism was discussed. Related material is also carried out on one of the photocatalytic of degradating simulated pollutants and electrochemical properties.The specific contents of this thesis are as follows:In first chapter, we mainly introduced the definition, properties, preparation methods and characterization of nano-materials, and a simple overview on the hierarchical and heterogenous nanostructure materials'synthesis and growth mechanism. And we also briefly introduced the applications and its mechanism and research status of photocatalytic and lithium ion battery respectively. In second chapter, we introduced the synthesis, characterization and the possible formation mechanism of Ga-doped ZnO/SA-NCs as well as the photocatalytic properties of its application in degradation of Rhodamine B. Dandelion-like Ga-doped ZnO/SA-NCs consisting of parallel nanorods with the diameter of 20-50nm, length 1-4μm have been successfully prepared via a facile hydrothermal process. The amount of gallium metal and reaction time were all investigated to explore the possible formation mechanism of Dandelion-like Ga-doped ZnO/SA-NCs. The results show that the gallium has a great influence on the morphology of the product, if it does not participate in the reaction that would be formation of nano-sheet sample, the length of the nano-rods is variable with the time added. On the basis of these results, the possible formation mechanism of Dandelion-like Ga-doped ZnO/SA-NCs was proposed as follow:products of the precursor decomposition attached to the gallium droplets surface, and gallium droplets participate in a chemical reaction in the sample generated while transmission decomposition products to supply nanorods constantly grow, and finally the reaction end of the gallium droplets eventually run out. In order to investigate the photocatalytic effect of the dandelion-like Ga-doped ZnO/SA-NCs, photodegradation of rhodamine B based on dandelion-like Ga-doped ZnO/SA-NCs as the photocatalyst was tested, and the photodegradation rate of rhodamine B is up to 60% under Xe lamp irradiation.In third chapter, we introduced the synthesis, characterization and the possible formation mechanism of novel 3-D SnO2@C core-shell nanochains materials as well as its application in lithium ion battery. Nanochains composed of SnO2@C core-shell nanospheres (50-80 nm in diameter), which are consisting of carbon shell with the thickness of 2-10 nm and the SnO2 nanoclusters as the core with 6 nm diameter around of SnO2 NPs have been successfully prepared via a facile hydrothermal process. And the flow rate of the protection gas of the roasting process and the calcination temperature, time, dosage of glucose were all investigated to explore the possible formation mechanism of 3-D SnO2@C core-shell nanochains superstructure. The results showed that the key of obtaining SnO2@C core-shell structure is SnO2@C precursor undergo high temperature with small shielding gas flow rate. Different thickness of carbon shells will be achieved via adjusting the amount of glucose in hydrothermal process. And the structure of the sample will not change with the roasting time added but SnO2 nanoparticles slightly larger than before. Based on these results, we hypothesized that carbon polymers play a major role in 3-D SnO2@C core-shell nanochains superstructure formation process. Appropriate content of carbon not only can be dispersed aggregated SnO2 into nanoclusters but also as the connection media between SnO2 NPs, and the outer carbon shell promote the formation of the nanochains as a protective layer. In order to investigate the electrochemical properties of these SnO2@C core-shell nanochains, lithium ion battery based on different carbon shell of SnO2@C core-shell nanochains as the anode material was prepared, and the electrochemical properties of battery was tested as well. The results showed that SnO2@ C nanochain material electrodes with 8 nm carbon layer shell, under 300 mA/g current density, the battery capacity still as high as 650 mAh/g after 100 charge and discharge cycles.In forth chapter, we introduced the synthesis, characterization and the possible formation mechanism of the mesoporous carbon polyhedron material. We introduced a simple silica template-free route for the synthesis of a novel carbon monolith that was composed of unique mesoporous carbon polyhedrons (MCPs) in close-packed model, and which can be spontaneous into bulk material but no binder. These MCPs were evolved directly from colloidal carbon microspheres (CCMs) by using a new Li2CO3-moltensalt strategy, and the shapes of MCP monolith are engineerable into desirable structure models via a facile injection molding technique in precursor stage. The concentration of reactants, the calcination temperature and time were all investigated to explore the possible formation mechanism of MCPs. The results show that the sample calcination temperature and heating rate have a great influence on the pore sizes of the product. On the basis of these results, the possible formation mechanism of MCPs was proposed that consecutive DMF-swelling, Li-embedding and Li-dislodging Li2CO3-moltensalt strategy, for the growth of mesoporous carbon materials. It is also indicated that the MCPs material has broad application prospectsIn fifth chapter, a conclusion and a prospect of this thesis were presented. |
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