Preparation Of Ag @ SiO 2 / LaF : Eu ^{3 +} Nanostructures And Study On Surface Enhancement Fluorescence Effects

Noble metal nanoparticles show good near-field enhancement effect with the excitation of outside light field, which can regulate the behavior of Raman and fluorescence spectra for molecules around its surface. Currently, the study of surface enhanced fluorescence focues on the effects of organic dye molecules, but the research on rare earth doped nanomaterials enhanced fluorescence are relatively less reported. The core-shell structure nanocomposites, in which the noble metal is nuclear and rare earth doped compound is shell, can effectively improve the spectral radiation efficiency of fluorescent molecular. It can satisfy the actual requirements of the biological probe and have broad prospect of application in the biological sensors.In this thesis, we prepared Ag@SiO2/LaF3:Eu3+nanoparticles and SiO2/LaF3:Eu3+nanoparticles successfully through the high temperature solvothermal method, sol-gel method, and precipitation method. We uesd laser spectroscopy techniques to study the influence of the isolation layer on for surface enhanced fluorescence effect. The main points are divided into the following two parts:In the first part, we studied a series of the preparations of samples (Ag@SiO2/LaF3: Eu3+, SiO>2/LaF3:Eu3+). First of all, we adopted the high temperature solvothermal method to prepare Ag nanoparticles by controlling the temperature of reaction and time, regulating the ratio between ethylene glycol and polyethylene pyrrolidone, which is restoring silver nitrate by ethylene glycol. We prepared the Ag nanoparticles whose morphology was normal, good dispersiveness. The diameter of the parpared particle was about60nm. Then we used an improved Stober method to prepare the Ag@SiO2nanoparticles with different thickness of silica shell. The thickness was controled by organizing the content of TEOS and ammonia. Finaly, the precipitation method was used to prepare Ag@SiO2/LaF3:Eu3+nanocomposites. In order to institute the spectral behavior of the nanoparticles, we used the wet chemical method to prepare the control group of SiO2/LaF3:Eu3+nanocomposites. The characterization results showed that the Ag@SiO2/LaF3:Eu3+nanocomposites and SiO2/LaF3:Eu3+nanocomposites are spherical structure and they have good dispersion.In the second part, we studied the fluorescence radiation behavior of SiO2/LaF3: Eu3+nanocomposites through the method of laser spectroscopy. Under the excitation of532nm continuous laser, we studied the spectral properties of nanocomposites with different thickness of SiO2shell. We found that the fluorescence intensity of Ag@SiO2/LaF3:Eu3+nanocomposites enhanced obviously, and the fluorescence enhancement amplitude are affected by the thickness of the insulating layer. When the thickness of SiO2isolation layer is about10nm, fluorescence enhancement factor is about4.7times.According to the study, we can obtaine the efficient enhanced fluorescence radiation with spherical core shell configuration and regulation of the SiO2isolation layer thickness.