Synthesis Of Rare Earth Mesoporous Materials And Their Photoluminescence Properties

Mesoporous materials with the ordered mesopores, various topologies, tailored pore size, controllable morphologies, high surface and large pore volume, can be wide used in the catalysis, bio-medicine, energy, sensors, material synthesis, and so on. In recent years, mesoporous materials combined with the optical, electrical and magnetic properties play an important role in the absorption/desorption, storage, carrier, tracing, and targeted. Rare earth elements with special electronic and optical properties are the important component of photoluminescent materials. Therefore, in this thesis the synthesis methods for the rare earth mesoporous materials combined with the luminescent property were studied, in order to get a new approach to prepare the rare earth mesoporous materials for more potential application.1. Studies on the synthesis of mesoporous rare earth phosphates and their luminescence properties. Based on the nanocasting route by hard-template, an improved method for preparing mesoporous materials has been brought forward by solving the indiscerptible solid precursor to get a uniform and stable precursor solution with soluble multi-component. During the infiltration process to progressively concentrate the precursor ions, capillarity drives the formation of precipitation inside the channels of silica hard template; after calcination and removing the hard template, mesoporous ordered YPO4 replica by reverse has been prepared. After YPO4 was doped with the appropriate lanthanide ion (such as Eu3+, Tb3+, and Ce3+), mesoporous YPO4:Ln3+ materials with the tunable intense optical properties (such as red, green and blue emission) were obtained.2. Synthesis of hexagonal (p6mm) and cubic (Ia3d) rare earth vanadate by means of improved nanocasting route by hard-template and study on the photoluminescence change between different topology mesostructures of YVO4:Eu3+. The results show that, there are different quenching concentrations for two cubic and hexagonal mesoporous YVO4:Eu3+ samples, for instance, the highest PL intensity of the cubic mesoporous YVO4:Eu3+(8 mol%) can be observed and the hexagonal one is 5 mol% Eu3+, which suggest that the different mesoporous channels of the cubic and hexagonal mesoporous YVO4:Eu3+ lead to different produced defaults and available surfaces for absorption of the UV light by the mutual interaction Eu3+ ions. 3. Study on the synthesis of layered ordered organic-inorganic hybrid rare earth materials and their luminescence properties. The results show that, the sample obtained under polar aqueous solution by template assembly has higher ordered layered structure, better crystallinity and stronger luminescent intensity than the samples obtained in ethanol solvent and the sample prepared by a precipitation method. It suggests that higher ordered layered structure and better crystallinity take benefit of the luminescence of the hybrid rare earth materials. And this long alkyl hybrid luminescent material with lipophilicity shows good green luminescent intensity in oil medium.4. Synthesis of Ln2O3@SiO2 compounds that the rare earth oxide supporting in spherical, polyhedral, and rod-like shape silica. The effect of silica supports with different morphology and channel on Ln2O3 luminescent properties was investigated by changing the temperature and Ln loading concentration. The results show that the effect of calcination temperature is almost same for the different complexes, that is, high temperature results in collapse of mesoporous structure and the phase transition of rare earth oxides and silica support after calcination at 1000℃. The loading amount of rare earth oxides is the minimum on the spherical silica support, the maximum on the rod silica support, and between the former two on the polyhedron silica support. It means that there are different luminescence properties corresponding to the rare earth oxides loaded on the different morphological silica supports.Mesoporous materials will satisfy more ingenious and specific requirement in future applications, and the diversified materials with different topological mesostructures should be further studied. In this thesis, the rare earth materials with multiple topological mesostructures have been studied and compared in the luminescent properties, which is very meaningful for the preparation and utilization of multi-functional rare earth materials.