A silica sol-gel design strategy for nanostructured metallic materials.

Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol-gel process. The porous materials made by silica sol-gel chemistry are typically insulators, however, which has restricted their application. Here we present a simple, yet highly versatile silica sol-gel process built around a multifunctional sol-gel precursor that is derived from the following: amino acids, hydroxy acids or peptides; a silicon alkoxide; and a metal acetate. This approach allows a wide range of biological functionalities and metals--including noble metals--to be combined into a library of sol-gel materials with a high degree of control over composition and structure. We demonstrate that the sol-gel process based on these precursors is compatible with block-copolymer self-assembly, colloidal crystal templating and the Stöber process. As a result of the exceptionally high metal content, these materials can be thermally processed to make porous nanocomposites with metallic percolation networks that have an electrical conductivity of over 1,000 S cm(-1). This improves the electrical conductivity of porous silica sol-gel nanocomposites by three orders of magnitude over existing approaches, opening applications to high-current-density devices.