单分散SiO_2/TiO_2/SiO_2多层复合微球的制备

采用一种以醇盐水解法为基础的生长硅溶胶的方法，制备了粒径为２００ｎｍ的单分散二氧化硅球形颗粒，并将其作为核心，利用常温连续进料的钛酸丁酯水解的多步法，在二氧化硅核心外经多次包覆形成厚层二氧化钛；在正硅酸乙酯的水解和陈化环境下，将上述ＴｉＯ２／ＳｉＯ２复合颗粒外再包覆一薄层二氧化硅，形成一种高折射率，可用于组装光子晶体的ＳｉＯ２／ＴｉＯ２／ＳｉＯ２多层复合微球．对该复合微球用重力沉降法、透射电镜法（ＴＥＭ）、Ｘ射线能谱分析法（ＥＤＳ）进行了表征．其中，重力沉降法是一种将Ｓｔｏｋｅｓ公式为基础推导的复合颗粒的粒径与沉降速度关系式所得的一系列数据进行拟合外延，来测定复合颗粒的粒径及包覆厚度的方法．

Preparation of Monodisperse SiO_2/TiO_2/SiO_2 Multiply Coated Submicrospheres

The monodisperse SiO2/TiO2/SiO2 multiply coated submicrospheres with uniform size, high refractive index and easily assembling property for constructing photonic crystals were prepared. The multilayer complex submicrosphere consisted of a colloidal silica sphere as core, a thick titania coating, and a outermost, thin coating of silica. Monodisperse colloidal silica spheres with 200nm in diameter were synthesized through the hydrolysis of tetraethyl orthosilicate(TEOS) in aqueous ethanol solutions with ammonia as catalyst. The titania coating about 40nm thick on silica cores was formed by the hydrolysis of titanium n-butoxide(TBOT). The hydrolysis of tetraethyl orthosilicate (TEOS) was still used to get the outermost silica coating about 10nm thick on titania coated silica submicrospheres. The SiO2, TiO2/SiO2 and SiO2/TiO2/SiO2 submicro- spheres were characterized with transmission electron microscopy(TEM), energy dispersive X-ray fluorescence spectroscopy(EDS), and the method of gravity sedimentation separately.