The light emission is the result of a process called "electron-hole recombination." By running an electric current through a carbon nanotube -- a long, hollow cylindrical molecule that is only one and a half nanometers (a billionth of a meter) in diameter -- negatively charged electrons in the nanotube molecule combine with positively charged "holes," which are locations in the molecule where electrons are missing. When an electron fills a hole, it emits a photon -- a tiny burst of light.

"We produced infrared light by applying voltages to a specific type of nanotube such that many electrons and holes end up in the nanotube, where they combine. This makes the nanotube the world's smallest electrically-controllable light emitter," said James Misewich, a materials scientist at Brookhaven.

"It's an exciting result, and my colleagues and I plan to continue studying the effect to determine the mechanisms behind it. For example, we hope to understand how to make the nanotubes emit other types of light, such as visible light, and how to increase the efficiency of the emission."

Carbon nanotubes do not yet have any mainstream practical applications, but researchers are investigating ways to use them in flat-panel displays, such as televisions and computer monitors, or as reinforcements in building materials, due to their exceptional mechanical strength.

Misewich also suggested that, if additional research leads to an increased efficiency of nanotube light emission, the nanotubes could possibly be used in lighting applications.

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