Mesoscopic Silica Thin Films Via Template-Assisted Self-Assembly

Abstract

Synthesis of mesoscopic silicates has stimulated considerable interest as a biomimetic approach to the fabrication of organic/inorganic nanocomposites. However, for future applications of these materials, controlled shapes and patterns, particularly as continuous thin films, rather than the microscopic particulates, need to be processed. Recently, we have described a synthesis scheme, using the supramolecular assemblies of surfactant molecules as a template for the condensation of inorganic species, to prepare silica mesoscopic thin films at a solid interface from a bulk solution. Here, we concentrate on the growth of such thin films and the effect of the template on the nanostructure formation.We employed tetraethoxy silane (TEOS), dissolved in acidic solution, as a silicate source and cetyltrimethyl ammonium chloride (CTAC) as the templating surfactant. Typical molar ratio was 1 TEOS : 1.2 CTAC : 9.2 HC1 : 1000 H2O. Concentrations of TEOS and HCl in the mixture were approximately l/7th of those for typical particle synthesis scheme, in order to sufficiently slow down the rate of TEOS hydration such that homogeneous nucleation is effectively switched off.