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 catalysis^1,2, separation technology³ and biomaterials engineering^4,5. Ordered arrangements of porous channels have been produced in silica-based materials by post-synthetic removal of surfactant templates from inorganic–organic mesostructures^6,7. 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 subtilis^8,9, can be used to extend the length scale of inorganic materials patterning. We produce ordered macroporous fibres of either amorphous silica or ordered mesoporous silica^6,7 (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.