Synthetic Macroporous Silicas with Multilamellar Structure

Abstract

We report a novel mixed-surfactant-based synthesis for growing new macroporous forms of silica. The dominant morphology is a fairly regular honeycomb-like construction with roughly 0.5−3-μm pores and 100−200-nm silica dividing walls. These walls consist of mesoscopic multilamellar structures. Interference optical microscopy observation and 23Na and 13C magic-angle spinning NMR diagnosed the single- and double-tailed surfactants with opposite charges on their headgroups, producing equilibrium vesicles spontaneously. A model that accounts for the architecture of the multilamellar silicas with macroporous morphologies involves the deposition of silica in the interfacial regions of contiguous assemblies of silicate−surfactant vesicles. Synthesizing shapes over μ-length scales provides new opportunities for understanding nature's biosilicification processes and potential uses where macroscopic form determines function, such as the separation, sensing, release, and catalysis of macro- and biomolecules.