Future brightens for carbon nanotubes.

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 Federale 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.