Oxide formation on biological nanostructures via a structure-directing agent: towards an understanding of precise structural transcription

Biomimetic silica formation is strongly dependent on the presence of cationic amine groups which hydrolyze organosilicate precursors and bind to silicate oligomers. Since most biological species possess anionic surfaces, the dependence on amine groups limits utilization of biotemplates for fabricating materials with specific morphologies and pore structures. Here, we report a general aminopropyltriethoxysilane (APTES) directed method for preparing hollow silica with well-defined morphologies using varying biotemplates (proteins, viruses, flagella, bacteria and fungi). Control experiments, pH evolution measurements and Si-29 NMR spectroscopic studies have revealed a mechanism of the assembly of APTES on bio-surfaces with subsequent nucleation and growth of silica. The APTES assembly and nuclei formation on bio-surfaces ensured precise transcription of the morphologies of biotemplates to the resulting silica. This method could be extended to the preparation of other oxides.