Hank Williams made a hit out of Clarence William’s song, “My Bucket’s Got a Hole in It,” in which the defect made the bucket unsuitable for transporting adult beverages. As it turns out, scientists would love to be able to make buckets with holes, albeit on a microscopic scale.
Porous films with nanostructures present many advantages. Perhaps the most important one is that they provide a greatly increased surface area where chemical reactions and other processes can take place. Scientists have developed many such materials, but success has remained elusive for one class of materials: metals. A porous metal film with nanostructures could be used as a catalyst to speed reactions, such as those required by fuel cells. Even more important would be the material’s ability to conduct electricity.
Researchers at Cornell have announced a new process by which they can create such materials using just about any metal you’d want. They use a “sol-gel” process to create a porous silicon material, which creates thin films of glass. It was difficult to get the metal atoms to “stick” to the silicon. About 10 years ago, a doctoral student realized that amino acids could be used as intermediaries because their molecules can have one end with an affinity for the silicon, and the other end for the metal.
The new process relies on the self-assembly characteristics of the materials involved. As Ulrich Wiesner, the Spencer T. Olin Professor of Engineering describes it, they have created a “one-pot mix-and-heat approach” that can be tuned to create different compositions, nanostructures, and performance characteristics such as conductivity. The researchers have demonstrated nanostructure silicon films with copper, nickel, iron, magnesium, cobalt, platinum, and chromium, among others.
The end result is a nanostructure film that contains a metal, silica (silicon dioxide), and carbon. It is possible to remove either or both the silica and carbon from the metal, or leave them in place to provide added stability or other useful properties. These new films can conduct electricity up to 1,000 more effectively than previous materials. As a result, these could be helpful in a wide range of alternative energy applications from fuel cells to photovoltaic panels, as well as other biomedical and engineering uses.