Preparation of monodisperse silica particles with controllable size and shape

The effects of dilution of tetraethyl orthosilicate (TEOS) with ethanol on the shape and monodispersity of silica particles were investigated. The results indicated that the dilution of TEOS with ethanol can depress the formation of new nuclei and the aggregation or adhesion of particles and make the distillation of TEOS unnecessary to achieve monodispersed silica spheres. A seeded growth technique using continuous drop addition of TEOS diluted with 4x volume of ethanol was developed to improve monodispersity and spheric shape and increase the size of silica particles. The monodisperse silica particles (150 nm +/- 5%-1.2 mum +/- 1%) with fine spheric shape were successfully synthesized by the seeded growth technique. Using the homemade 280 nm +/- 2.8% silica spheres, we prepared opals of high quality which showed periodically ordered packing and a photonic band-gap effect.