Positioning growth of scalable silica nanorods on the interior and exterior surfaces of porous composites

A novel yet straightforward one-pot synthesis technique was developed to grow silica nanorods on the interior and exterior surfaces of a porous, inorganic scaffold. Growth of the rods on the surface, versus in the bulk, was achieved by functionalizing the surface with chlorosilane molecules, which allowed the emulsion droplets in which the nanorods grow to anchor to the surface. Rods of 100-200 nm diameter and up to 2 mm in length could be grown uniformly over the surface with a typical surface density of 3 rods per mu m(2), resulting in an order-of-magnitude increase in the specific surface area (area per mass) of the porous material. It was also shown that the properties of the rods (e.g., size, surface density, shape) could be controlled by changing either the composition of the substrate material or the concentrations of key components in the reacting mixture. Furthermore, by selectively controlling the spatial location of the chlorosilane surface groups, the rods could be grown in specific locations inside the porous material.