(657c) Hierarchically Structured Membranes With Oriented Pores for Bio-Inspired Separations

                            Hierarchically Structured Membranes with Oriented Pores for Bio-Inspired Separations

Authors: Silo Meoto (Presenter), Marc-Olivier Coppens

Protein channels in cell walls are remarkably efficient for separations, showing high permeation of, and selectivity for a desired species. Examples include AQP1 (water channel) and KcsA (potassium channel). Knowledge of the physico-chemical principles that are responsible for the superior performance of such biological nanopores could be applied to the design of artificial membranes with similar properties. We discuss the development of an inorganic membrane with ordered arrays of oriented nanochannels, whose diameter and surface chemistry can be tailored to enhance and control separation selectivity.

A hierarchically structured membrane has been synthesized, with nanochannels of silica grown inside a macroporous support. Using a soft-templating method, the silica grows around cylindrical micelles, formed from a surfactant, which act as structure-directing agents. Silica with cylindrical nanopores is obtained upon removal of the surfactant. A systematic design was used to ensure that the pore channels of the macroporous support are filled tightly with silica nanostructures, guaranteeing uniformity over macroscopic distances across the support. Based on the mechanism underlying the performance of biological nanopores, desired functional groups have been tethered to the inner surface of the confined silica nanochannels to create similar steric and electrostatic interactions. Membrane permeability and selectivity were investigated as a function of pore size and charge effect, created by different chemical functional groups.

The fabricated membrane was characterized by small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption/desorption measurements after the removal of the surfactant. Membrane performance was tested by representative bio-separations.