Controlled silica synthesis inspired by diatom silicon biomineralization

Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes, resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a target for many researchers, is already realized in the formation of diatom biosilica, producing highly hierarchical ordered meso- and macropores silica structures. This notion formed the starting point in our integrative biomolecular and biomimetic study on diatom silicon biomineralization in which we have analyzed silica transformations and structure-direction in polymer-mediated silica syntheses using a combination of (ultra)small-angle X-ray scattering and (cryo)electron microscopy. Using bio-analogous reaction conditions and reagents, such as waterglass and (combinations of) polyethylene oxide (PEO) based polymers, we demonstrate in this review the synthesis of tailormade mesoporous silicas in which we can, as in biosilica synthesis, control the morphological features of the resulting materials on the nanometer level as well as on the micrometer level.