Future brightens for carbon nanotubes

Jessica Gorman

For the first time, researchers have used the unusual electronic properties of carbon nanotubes to make a lightbulb glow.

The scientists used multiwalled carbon nanotubes, each made up of many nested cylinders of carbon. Other researchers have used carbon nanotubes as tiny electron guns in flat electronic displays, but until now, no one had made a lightbulb based on nanotubes, says Jean-Marc Bonard. His team at the Ecole Polytechnique de Fédérale de Lausanne in Switzerland reported the innovation in the April 30 Applied Physics Letters.

To make the prototype, the researchers grew nanotubes on a metal wire and placed it in a glass cylinder. When they applied voltage, the nanotubes emitted electrons, which struck a phosphorescent coating inside the glass bulb.

Fluorescent bulbs work on a similar principle, but the nanotube lamp has advantages. Unlike fluorescent lights, the nanotube device comes on instantly, dims easily, and doesn't contain toxic mercury vapor (SN: 7/19/97, p. 44).

There's a problem with nanotube bulbs, however. Currently, the prototype uses 10 times as much power as a fluorescent bulb of similar luminance does. Bonard is testing different phosphorescent materials in search of higher efficiency.

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References:

Bonard, J.-M., et al. 2001. Field emission from cylindrical carbon nanotube cathodes: Possibilities for luminescent tubes. Applied Physics Letters 78(April 30):2775.

Further Readings:

Wu, C. 1997. New phosphor for fluorescent bulbs. Science News 152(July 19):44.

Sources:

Jean-Marc Bonard
Institut de Physique Experimentale
Department de Physique
Ecole Polytechnique Fédérale de Lausanne
CH-1015 Lausanne EPFL
Switzerland

From Science News, Volume 159, No. 21, May 26, 2001, p. 335.