Oct 2 2009
A branch of nanotechnology that showed great initial promise nearly 20 years ago could get a fresh look because researchers at the University of Louisville, Purdue University and Honda Research Institute USA Inc. have created a better "recipe" for making microscopically tiny structures with more predictable, desirable properties - and potential for advances such as enhancing the efficiency of solar cells for energy use.
The research findings, initiated and funded by Honda, are set to be published Oct. 2 in Science, a publication of the American Association for the Advancement of Science.
Previously, scientists had grown carbon nanotubes but couldn’t control whether they would occur as one of two types - semiconducting or metallic, for different uses - because the process was random. The metallic nanotubes are more useful as building blocks that connect other nanostructures or for windows for solar cells or other devices with optical and electrical qualities.
"This is the first report that demonstrates that we can control fairly systematically whether carbon nanotubes are metallic or semiconducting," said Avetik Harutyunyan, the Honda Research Institute principal scientist who led the research. "We have a 91 percent success rate of producing metallic nanotubes."
Honda researchers discovered they could control whether the carbon nanotubes become metallic or semiconducting by using either argon or helium as "carrier gases" during the process. Researchers at UofL used the technique to make large quantities of nanotubes and precisely measure whether they were metallic or semiconducting. Purdue researchers took high-resolution images with a transmission electron microscope to help determine why the process worked.
Lead UofL researcher Gamini Sumanasekera, an associate professor of physics, said he hoped the findings will renew interest in the field. Carbon nanotubes may replace more commonly used materials for purposes that require electrical conductivity and good light transmission, he said.
Besides Harutyunyan and Sumanasekera, the paper’s authors were Gugang Chen, Elena Pigos and Oleg Kuznetsov, Honda; Tereza Paronyan and Kapila Hewaparakrama, UofL; and Seung Min Kim, Dmitri Zakharov and Eric Stach, Purdue.