Researchers at the University of California, Riverside have shown for the first time that carbon nanotubes in a vacuum show excellent conductivity and can be very effective infrared detectors because of their high sensitivity to light.

The findings are published in a paper titled Bolometric Infrared Photoresponse of Suspended Single-Walled Carbon Nanotube Films, in today's edition of the journal Science, co-authored by UCR researchers Mikhail Itkis, Ferenc Borondics and Aiping Yu, and led by Distinguished Professor of Chemistry and Chemical and Environmental Engineering Robert Haddon. The research was conducted 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.

"What you have is a substance that is very efficient at collecting light and converting that energy to heat," Haddon said. "You have a material that is really well designed to function as an infrared detecting device."

The 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 in nighttime situations. For scientist, the discovery could be beneficial for infrared spectrometry and astronomy.

The UCR findings contradict previous studies of the photoconductivity of carbon nanotubes, which showed that when 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 millimeter 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 - 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 added. Placing the nanotube strip in a vacuum also eliminates heat loss via the air.