Newman Professor of Chemistry and Chemical Biology, and Sol Gruner, the John L. Wiesner and two Cornell colleagues, Francis DiSalvo, the J.A. In principle, if you can do it with one metal you can do it with mixtures of metals." "It opens a completely novel playground because no one has been able to structure metals in bulk ways. The new thing we have added is the ligand, which creates high solubility in an organic solvent and allows the particles to flow even at high density."Īnother key factor, he added, is to make the layer of ligand surrounding each particle relatively thin, so that the volume of metal in the final structure is large enough to hold its shape when the organic materials are removed. "But metals have a tendency to cluster into uncontrolled structures. "The polymer community has tried to do this for 20 years," said Ulrich Wiesner, Cornell professor of materials science and engineering, who, with colleagues, reports on the new method in the June 27 issue of the journal Science. When the polymer and ligand are removed, the metal particles fuse into a solid metal structure. The method involves coating metal nanoparticles - about 2 nanometers (nm) in diameter - with an organic material known as a ligand that allows the particles to be dissolved in a liquid, then mixed with a block co-polymer (a material made up of two different chemicals whose molecules link together to solidify in a predictable pattern). Applications include making more efficient and cheaper catalysts for fuel cells and industrial processes and creating microstructured surfaces to make new types of conductors that would carry more information across microchips than conventional wires do. Now, Cornell researchers have developed a method to self-assemble metals into complex nanostructures. Right, electron microscope photo of the actual structure.įor 5,000 years or so, the only way to shape metal has been to "heat and beat." Even in modern nanotechnology, working with metals involves carving with electron beams or etching with acid. Computer simulation, left, shows how platinum nanoparticles will fuse into a structure with tiny pores after the polymers that guide them into position are removed.
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