中文摘要：

采用直接沉淀法成功制备了Ag@SiO2@GdF3：Er，Yb核壳结构纳米上转换发光粒子，并用XRD，TEM，UV-Vis，FTIR以及荧光光谱等对其结构和发光性能进行了表征．XRD分析表明：Ag表面包覆上了结晶良好的正交晶系的GdF3：Er，Yb．TEM照片显示：制备的复合纳米粒子具有明显的球形核壳结构，内核Ag粒子的直径约50nm左右，包覆后的Ag@SiO2@GdF3：Er，Yb粒径约为80～120nm，表面光滑且包覆完全．UV-Vis光谱证明：GdF3：Er，Yb和SiO2成功包覆在Ag核表面，包覆后Ag纳米粒子的表面等离子体共振吸收峰发生了红移．荧光光谱表明：在980nm激光激发下，该复合纳米粒子显示出和纯的GdF3：Er，Yb相同的Er3＋的特征红色和绿色上转换发光，以位于655nm处的Er3＋离子的4F9／2→4I15／2的红光发射最强，并且复合粒子的发射光强度比纯的GdF3：Er，Yb有所增强．

英文摘要：

Noble metal nanoparticles such as Ag or Au and rare earth ions doped-up-conversion luminescence materials are all potential in the fields of biological labeling and sensing, diagnosis and biotherapy. When coupling with them together to form core-shell structure composites, noble metal nanostructures will present the strong surface plasmon resonances （SPRs）, they can act as the function of ＂antenna＂, that is they can transfer the absorption energy to the luminescence particles and enhance their luminescence intensities. Moreover, when positioned in close proximity to metal surfaces, the luminescence materials can exhibit optical property changes （quenching or enhancement of luminescence）, likely a result of the changed near-field electro-dynamical environment around the metal that arises from the collective oscillation of conduction electrons. This is a perfect model for studing the effects on luminescence properies of metal and luminescence materials. In this article, Ag nanoparticles were prepared by a glycol reduction method, and SiO2 spacers were coating on the surface of Ag nanoparticles by modified Stober method, at last, the core-shell structure Ag@SiO2@GdF3：Er,Yb up-conversion luminescent nanopartitles were successfully synthesized by direct precipitation method. The structure and luminescence property of the samples were characterized by XRD, TEM, FTIR, UV-Vis and fluorescence spectra. XRD patterns show that the orthogonal phase GdF3：Er,Yb nanocrystals are coated on the surface of Ag cores. TEM images present that the obtained composites have obvious spherical core-shell structure, the diameter of the Ag core is 50 nm, the size of the Ag@SiO2@GdF3：Er,Yb composites is about 80- 120 nm, the surface is smooth and the coating is complete, GdF3：Er,Yb nanoparticles are found obviously in the shell. UV-Vis spectra indicate that GdF3：Er,Yb and SiO2 are coated successfully on the surface of Ag, which increased the refractive index of local area around Ag nanoparticles, and the surface plasma