Expanding properties

A new method to modify the structure of single-walled carbon nanotubes - one of the strongest structures known with unique electrical and thermal properties - could expand their electronic properties and open the path to nano-electronics.

This promising method to add defects to carbon nanotube walls was developed by researchers at the US Department of Energy's Argonne National Laboratory, who are interested in improving the materials for thermoelectric power generation, the use of heat differences to generate electricity. Thermoelectric conversion is the principle behind thermocouples, thermal diodes and solid-state refrigerators.

"If you change the electronic structure," said Argonne chemist Larry Curtiss, "by adding defects in an ordered way, theoretically you can make more efficient thermoelectric materials. So we could produce electricity more efficiently from solar, nuclear or any thermal power generation." Curtiss is group leader of the Molecular Materials Group in Argonne's Materials Science Division.

Creating defects by adding molecules to nanotubes is challenging because of their extremely small size. And researchers are seeking a controlled, reproducible method. So the Argonne team, which includes Curtiss, Michael Sternberg, Peter Zapol, Dieter Gruen, Gary Kedziora, Paul Redfern and David Horner, used computer simulation tools to learn how to add a single carbon dimer - a molecule of two bonded carbons - to a single-walled carbon nanotube.