Electrochemically assisted generation of silica deposits using a surfactant template at liquid/liquid microinterfaces

The electrochemically assisted generation of mesoporous silica deposits at arrays of microscopic liquid/liquid interfaces was investigated. Ion transfer voltammetry was used in order to initiate the formation of silica material by electrochemical transfer of template species (cetyltrimethylammonium, CTA(+)), initially present in the organic phase, to the aqueous phase containing the hydrolyzed silica precursors (tetraethoxysilane, TEOS). The deposition mechanism was investigated using cyclic voltammetry, based on the analysis of diffusion layer profiles of CTA(+) species from the organic side of the interface. The morphology of the deposits varied from hemispherical to almost flat with the potential scan rate, the spacing factor of the microinterfaces array supporting the liquid/liquid interfaces, or the initial CTA(+) and TEOS concentrations, as evidenced by scanning electron microscopy and profilometry analyses. The amount of deposited material can be related to the amount of CTA(+) species passing across the liquid/liquid interfaces. Confocal Raman spectroscopy was used to confirm the presence of surfactant-templated silica deposits and to analyze the effectiveness of calcination in removing the organic molecules filling the interior of the pores. After template removal, the mesoporous network became accessible to external reagents, as checked by interfacial alkylammonium cation transfer, suggesting a possible analytical interest of such modified micro-liquid/liquid interfaces.