Self-supporting hybrid silica membranes with 3D large-scale ordered interconnected pore architectures
A simple and versatile method to form transferrable self-supporting membranes with a hierarchically ordered arrangement of nanometer size pores has been developed. The method relies on the formation of an ordered 3D arrangement of latex spheres on a sacrificial support, proper infusion of a suitably prepared organic–inorganic hybrid sol, followed by template removal without membrane destruction. Initially, the mechanical properties of self-supporting membranes prepared by combining a bi-functional silane (i.e., dimethyldimethoxysilane, DMDMOS) with tetramethoxysilane (TMOS) in different mole ratios were studied by nanoindentation. As the amount of DMDMOS increased, the hardness and Young's modulus decreased while the ratio of the two first decreased and then increased. The surface morphology and roughness as evaluated by Atomic Force Microscopy (AFM) also increased with the DMDMOS to TMOS ratio. Using a mole ratio of 1 : 1 and a close-packed 3D array of polystyrene spheres as a template, a flexible and transferrable membrane containing an ordered arrangement of interconnected pores of well-controlled size was constructed. The diameters and number of layers of the 3D pore architectures were manipulated by changing the microsphere diameter and concentration. Surface pore diameters ranged in size from 110–300 nm while the diameters of the internal pores ranged from 60–140 nm depending on the size of the original template. The number of layers ranged from two to five. Such self-supporting membranes, with their unique hierarchical, interconnected pore architectures over a large length scale, can be transferred to other surfaces for potential and promising applications in the fields of filtration, sensing and catalysis.