A Study On Synthesis Of Silica Colloidal Crystals And Its Formation Mechanism

In recent years, colloidal crystal technology has attracted both chemical and physical scientists' interest. Colloidal crystal is also called photo crystal due to its periodical structure,it can be used as optoeletronic devices and photonic band-gap crystals. In the researching field of materials , colloidal crystal can be used as molecular templet to synthesis molecule sieves with micro porosity/ macro porosity.To control the colloidal particle size and its monodispersity is very important in developing two-and three-dimensional self-assembled structures where individual colloidal particle plays the role of building blocks - artificial atoms. Therefore, relatively simple and reproducible approaches for the synthesis of colloidal particles with controllable size are of great fundamental and technological interest. In the past decades, some nucleation mechanisms of monodisperse silica colloidal particles formation were put forward. But still none of the available nucleation mechanisms is able to explain all the experimental facts. In this contribution, based on the plenty of the present literatures and combining with the feature of our laboratory, we mainly carried out the following work and got some useful experimental results:1.Controling different reaction experimental conditions (the concentration of tetraethylorthosilicate, water and different reaction temperature), highly monodispersed silica colloidal particles with diameter range from 150nm to 800nm were synthesized freely. When the concentration of tetraethylorthosilicate was increased, the particle sizes increased; When the reaction temperature was increased, the particle sizes decreased; when the amount of water was increasd, the particle size increased ,then after a maximum value, the particle size decreased. The formation mechanisms of the resultant silica particles under different reaction conditions were carefully investigated and discussed.2.AFM, SEM, DLS and Microelectrophoresis instruments were used to study the size, size distrution,morphology and zeta potential of silica colloidal particles. Transimission spectrum identified different λ_max with silica particles of different size. 3.The effect of electrolyte additives to the Stober process was studied. Without electrolyte additives silica colloidal particles with diameter from 150nm to 800 nm were obtained by Stober process. When electrolyte additives were used in the system particle size decreased even to 60nm. Electrolyte additives also affect the size distribution and morphology of silica colloidal particles prominently.