A Study On Synthesis And Application Of Monodisperse Silica Colloidal Particles

In recent years, colloidal crystal has attracted both chemical and physical scientists' interest. Colloidal crystal is also called photonic crystal due to its periodical structure. It can be used as photocatalysed material, and also has potential applications in an optoelectronic functional material. Colloidal particles self-assembly is one of the most effective synthesis methods of large-scale photonic crystal with photonic band-gaps or pseudogaps in the near infrared-visible frequency regime.The control of the colloidal particle size and its monodispersity is very important in developing two-and three-dimensional self-assembled photonic colloidal crystals where individual colloidal particle plays the role in building blocks. Therefore, relatively simple and reproducible approaches for the synthesis of monodisperse colloidal particles are of great fundamental and technological interests. In this work, monodispered silica particles with controllable size were synthesized by seeded growth technique, i.e. an improved Stober method. The nucleation mechanisms of monodisperse silica colloidal particles were also studied. The surface character of the silica colloid particles is manipulated by a chemical graft of alkyl chains with silane coupling agents,3-methacryloxypropyltrimethoxy silane(WD-70). A simple method of self-assembling silica colloid particles was found. The surface modified silica colloid particles could be self-assembled to form three-dimensional opal photonic crystal in ethanol. The self-assembly conditions were stuided systematically. The silica particle diameters,monodispersity, degree of sphericity and characters of microstructures were characterized by SEM and FTIR. SEM and UV-Vis were also used to analyze the silica opal structure. The results indicate that self-assembled silica particles have well photonic crystal characteristic.Titania has extensive applications. However, titania powders with high ratio surface areas are not thermally stable and lose their surface area readily at elevated temperature through phase transformation and crystallite growth. In this work, SiO2 core and TiO2 shell composite particles with high surface areas were synthesized by sol-gel technique. The surface topography and the microstructures were analyzed by SEM and FTIR. Silica and titania composite materials with special texture, such as hollow-rod and sheet structures, were also synthesized by sol-gel method. The SiO2 and TiO2 composites exhibit novel properties which were not found in either titania or silica.