Effect of surfactant on particle morphology for liquid phase deposition of submicron silica.

Liquid phase deposition (LPD) of silica from soluble silicates has been performed in the presence of dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS) and sodium dodecylbenzyl sulfate (SDBS). The morphology of the silica varies between semi-ordered uniform spheres to low porosity agglomerates, with the choice and concentration of the surfactants. The agglomerate structures depend on the charge of the surfactant (and hence the retention of micelles under acidic LPD conditions and/or the ionic character of the surfactant solution), the critical micelle concentration (as compared to the concentration of the silica precursor), and the ionic strength of the solution. The application of surfactant micelles as templates for LPD silica is counter to a previous proposal that suggested the ionic strength of the silicate solution would cause the collapse of the ionic vesicles. The size of spherical silica particles is controlled by the relative concentration of the surfactant and the LPD precursor.