Synthesis of silica spheres
|Stöber method allows to obtain suspensions of monodisperse silica spheres. The particle diameter can be accurately controlled through the parameters involved in the process (temperature, concentrations, etc.). TEM images show the high quality of the particles synthesised.|
The quality of the opaline structure dramatically depends on the monodispersity of the starting particles. So, the first requirement in order to build technologically interesting materials is to control the production of well-shaped size-controlled spherical silica particles. The synthesis of submicron silica particles has been extensively studied (1, 2). The most common method is that developed by Stöber et al.(3). It consists of a sol-gel process in which a Si metal-organic compound hydrolyses whereby Si-O chains are created and whose condensation leads to amorphous silica nanoparticles. Under controlled reaction conditions monodisperse spheres (less than 5% in dispersion) with diameters in the range between tenths of a micron and a micron can be produced. The figure shows a diagram of the chemical process along with transmission electron microscopy (TEM) images of the resulting silica particles.
1.- C.J. Brinker and G.W. Scherer. 1990. “Sol-Gel Science”. Academic Press Inc. New York.
2.- “The Colloid Chemistry of Silica”, Ed. H.E. Bergna. 1994. Adv. Chem. Series, vol. 234; Am. Chem. Soc., Washingon D.C.
3.- W. Stöber, A. Fink, and E. Bohn.1968. J. Colloid Interface Sci., 26, 62.