Study On Synthesis Hierarchical Superstructural Manganese Carbonate And Zinc Oxide With Schiff's Base As The Template And Their Application

Nanomaterials with hierarchical superstructures have shown great potential application in the fields of magnetic resonance imaging contrast agents, fluorescence probes, industrial catalysis, gas storage and adsorption, etc. so, the nanomaterials with hierarchical superstructures which self-assembled by the nanoparticles have become the hot topic of nanotechnology and nanoscience.In this thesis, we firstly synthesized a schiff's base, namely, p-phenylenediamine glycine, and then, the schiff's base was used as shape guiding-agent to build the hierarchical superstructures. The different superstructures could be generated by controlling the hydrothermal temperature, the molar ratio of manganous ions to the schiff base, or the volume ratio of water to ethanol. The growth mechanism was proposed based on the rod-dumbbell-sphere model. The contents of this thesis include three chapters as shown in the following:Chapter 1, we systematically reviewed the principle and the major categories of methods for preparation of nannomaterials and introduced the basic principle of hierarchical superstructures. And then, the plan of this thesis was proposed.Chapter 2, the synthesis of MnCO₃ hierarchical superstructures, such as chrysanthemum, straw-bundle, dumbbell and barbed sphere-like, in water/ethanol system under mild hydrothermal condition. In the synthesis process, the CO₂ in atmosphere was used as the source of carbonate ions and schiff base was used as shape guiding-agent. The different superstructures of MnCO₃ could be obtained by controlling the hydrothermal temperature, the molar ratio of manganous ions to the schiff base, or the volume ratio of water to ethanol. A tentative growth mechanism for the generation of MnCO₃ superstructures was proposed based on the rod-dumbbell-sphere model. Furthermore, the MnCO₃ as precursor could be further successfully transferred to Mn₂O₃ microstructure after heating in the atmosphere at 500oC, and the morphology of the Mn₂O₃ was directly determined by that of the MnCO₃ precursor. In additional, the MnCO₃ were coated with PVP to get the water solubility, the longitudinal relaxation rate (r₁) and magnetic resonance imaging (MRI) was investigated.Chapter 3, the synthesis of ZnO hierarchical superstructures by using the schiff base was used as shape guiding-agent under mild hydrothermal condition. The different morphologies of ZnO hierarchical superstructures such as spherical, irregular, flattened shape and lantern-like nanoflowers could been fabricated through controlling the temperature, ratio of water to ethanol and Zn²⁺ ions to Schiff base. The investigations of TEM and FESEM have confirmed that the ZnO hierarchical superstructures were self-assembled by small ZnO nanoflats with～100 nm. And then, the solid fluorescent spectrum showed that the flower-like ZnO superstructures has weak green emission centered at 540 nm.