| As present, the countries in the world regarded the development of nanotechnology as an important goal of national development. Nanotechnology is the technique for preparing nanomaterials. Nanomaterials refers to the ultrafine material, whose particle is between 1-100nm. Because of the grain's size and big specific surface area, nanomaterials has many special properties, such as small size effect, quantum size effect, surface effect, macroscopic quantum tunnel effect which bulk material do not have. Therefore, nanomaterials have received considerable attention due to their special physical and chemical properties in optics, mechanics, electrics, magnetics, calorifics, catalytic field, and have great potential for applications.In this study, simple and rapid solution procedures are developed for the synthesis of uniform Ag/ZnO nanoplates and MnO2 sea urchin nanostructures. The as-synthesized samples structure and morphology were characterized by multiple instrumental analyses. At the same time, the formation mechanism of the as-obtained products were also studied, and some meaningful conclusions being obtained. The following is the main content and results of this study:(1) First, simple solution procedures are developed for the synthesis of uniform ZnO nanoplates. The diameter and thickness of ZnO nanoplates are mainly determined by Zn(CH3COO)2-2H2O content. When the mass of Zn(CH3COO)2-2H2O is relatively high. The grain sizes of ZnO nanoplates are large. When the amount of Zn(CH3COO)2·2H2O is reduced. Then, the sizes of ZnO nanoplates become small. Second, we have successfully prepared Ag/ZnO composites by co-precipitation and photo-reduction method. The Rhodamine B (RB) solution is chosen as a model reaction to evaluate the photocatalytic activity and mechanism of different samples. The results indicated that the photocatalytic activity of Ag/ZnO heterostructure relates to Ag dispersion and amount of loading on the surface of ZnO nanoplates. The Ag/ZnO-PR displayed higher dispersion than Ag/ZnO-CP. The optimum Ag loading of Ag/ZnO-PR and Ag/ZnO-CP are 1 wt.% and 1.5 wt. %, respectively. Therefore, Ag/ZnO-PR displayed higher photocatalytic activity than Ag/ZnO-CP.(2) We provide a simple and facile hydrothermal method to synthesize highly 3D y-MnO2 sea-urchin shape nanostructures. The morphology of y-MnO2 is mainly determined by (NH4)2S2O8 content. When the mass of (NH4)2S2O8 is 1.83g, the obtained y-MnO2 exhibit homogenous sea-urchin shape structure, with diameter of 5-7μn. Based on the experimental results, the sea-urchin shape manganese oxides may grow according to a "nucleation-aggregate-growth" process. Next, we investigate the electrical properties of the as-synthesized sea-urchin shape y-MnO2 nanostructures in rechargeable Li-MnO2 cells. As a comparison, commercial manganese dioxide (C-MnO2) as cathodes has also been electrochemically tested under the same conditions. At a current rate of 50 mA g-1.The capacity of sea-urchin shape y-MnO2 and C-MnO2 are 188 mA h g-1 and 137 mA h g-1, respectively. After cycling at the current rate of 50 mA g-1 for 20 cycles, the sea-urchin shape y-MnO2 still retained an acceptable capacity of 101 mA h g-1, In contrast, the electrochemical performance of C-MnO2 in Li-MnO2 cells was undesirable, and the capacity quickly fell below 80 mA h g-1. Thus, the as synthesized sea-urchin shape y-MnO2 nanostructures display better charge-discharge properties as compared to the C-MnO2 when used as cathodes in Li-MnO2 batteries. Therefore, these nanocrystals with novel morphologies may also find potential applications in high-energy batteries field. |
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