Bacterial templating of ordered macrostructures in silica and silica-surfactant mesophases

Abstract

The synthesis of inorganic frameworks with specified and organized pore networks is of potential importance in catalysis1,2, separation technology3 and biomaterials engineering4,5. Ordered arrangements of porous channels have been produced in silica-based materials by post-synthetic removal of surfactant templates from inorganic–organic mesostructures6,7. The resulting pore sizes are commensurate with the packing dimensions of the organic molecules, and are currently limited to length scales of up to 10nm. Here we show how a bacterial superstructure, consisting of a thread of coaligned multicellular filaments of Bacillus subtilis8,9, can be used to extend the length scale of inorganic materials patterning. We produce ordered macroporous fibres of either amorphous silica or ordered mesoporous silica6,7 (MCM-41) by template-directed mineralization of the interfilament spaces followed by removal of organic material by heating to 600°C. The inorganic macrostructures consist of a macroporous framework of 0.5-μm-wide channels with curved walls of either silica or mesoporous silica, 50 to 200 nm in thickness. The formation of ordered pores in the MCM-41 replica on both the mesoscopic and macroscopic length scales illustrates how supramolecular and supercellular templates might be combined for the fabrication of inorganic materials with structural hierarchy.