The Preparation And Properties Of Surface Modified Rare Earth Doped Fluoride Nanoparticles

Rare earth doped luminescence nanoparticles have a series of outstanding advantages, wich have the potential and ability to overcome a number of problems associated with the commonly used luminescent lables.If the luminescent nanoparticles is to be the fluorescent markers, nanoparticles with hydrophilic surfaces are usually required, so the surface modification of the nanoparticles is very important.In this thesis, we developed several methods carrided out in methanol to synthesize surface modified rare earth doped PVP/LaF3 nanoparticles. Transmission electronic microscope (TEM), x-ray diffraction (XRD), photoluminescence spectroscopy (PL) were used to study the morphology, size,the crystal structure and surface property of the nanoparticles. In addition, the core-shell structure of silica-coated PVP/LaF3 nanomaterials were synthesized, We investigated the influence of coating thickness on luminescence intensity of the nanomaterials. The results show:(1) Polyvinypyrrolidone(PVP) is an amorphous amphiphilic polymer being with good solubility in polarity and non-polarity solvent and its active C=O groups can coordinate with rare earth ions. It can be use as both polymer and ligands to control the nanoparticles morphology and to improve their dispersion. We make full use of the advantage of PVP and synthesize PVP/LaF3:Ln (Ln=Eu3+,Sm3+,Tb3+) nanocomposite materials. It is revealed that these nanoparticles all have an average size of about 15nm and take well crystallized pure hexagonal phase. Besides Well-dispersed nanoparticles have a spherical shape and retain good hydrophilic property and show strong luminescence.(2) In order to reduce the surface of nano-particles in lattice defects, and further enhance the luminescent properties of nanoparticles. Polyvinypyrrolidone modified LaF3:Ln nanoparticles PVP/LaF3:Ln were prepared by solvothermal method. We investigated the influence of synthesis temperatures and reaction time on the luminescence intensity of the nanoparticles.The optimum reaction condition is found: 140℃,12h. Moreover, the nanoparticles prepared by the solvothermal method have a better dispersion and possess a stronger luminescent properties.(3) It was revealed that the core-shell structure can significantly improve the luminescence of quantum dot. PVP/LaF3:Eu3+@SiO2 core-shell structural nanocomposite materials were synthesized by a modified Stober method. We studied the influence of the amount of tetraethoxysilane (TEOS) on the crystal structure, size, morphology and luminescent property of the nanoparticles. The optimum amount of TEOS is found to be 0.30ml and the nanoparticles show the strongest luminescence when excited at 397nm. The core-shell structural nanocomposite we prepared have significant potential in biological labels.