Nanotubes in a Vacuum 'Excellent Conductors'

Carbon nanotubes in a vacuum show excellent conductivity and can be very effective infrared detectors because of their high sensitivity to light, according to a University of California, Riverside (UCR) research team.

Robert Haddon, a professor of chemistry and chemical and environmental engineering at UCR, led the research team that conducted the research at the Center for Nanoscale Science and Engineering, which is a part of the College of Natural and Agricultural Sciences and the Bourns College of Engineering at UCR. He and the other researchers -- Mikhai Itkis, Ferenc Borondics and Aiping Yu -- recently reported their findings ("Bolometric Infrared Photoresponse of Suspended Single-Walled Carbon Nanotube Films") in Science.

Haddon said findings could be of great interest to the military and law enforcement, which often need to use infrared detection technology to look for people and vehicles at night, and to scientists, for infrared spectrometry and astronomy.

The UCR findings contradict previous studies of the photoconductivity of carbon nanotubes, which showed that when they were irradiated with light, carbon nanotubes had a weak response, suggesting low photoconductivity. However, those previous experiments placed the carbon nanotubes on a substrate that acted to dissipate much of the heat built up by irradiation, Haddon said.

The UCR experiment placed a .5-mm strip of purified carbon nanotubes that were suspended across two electrodes in a vacuum, with no substrate to dissipate the heat. The results generated anywhere from five to 10 orders of magnitude (105 to 106) of the amount of heat found in previous tests.

"We think this is due in large part to the lack of a substrate, which works like a heat sink to absorb much of the heat buildup," Haddon said. Placing the nanotube strip in a vacuum also eliminates heat loss via the air, he said.

For more information, visit: www.engr.ucr.edu