A simple flash of light sets high-tech carbon fibers alight, a young researcher has found. The effect adds to the list of the fibers' remarkable properties and could have applications in fields ranging from rocket science to nanotechnology.
With a little coaxing, carbon atoms can arrange themselves in tubes resembling atomic-scale cylinders of chicken wire. Such single-walled carbon nanotubes are among the strongest materials known, can carry electricity like the metals in wires and the semiconductors in silicon chips, and can even be made to conduct electricity with no resistance. Such properties could someday allow nanotechnologists to fashion tiny electrical circuits and mechanical devices out of nanotubes. Now, single-walled carbon nanotubes have displayed another novel property: They catch fire when exposed to a simple flash of light.
The discovery was made by undergraduate Andres de la Guardia while working with Pulickel Ajayan, a materials scientist at Rensselaer Polytechnic Institute in Troy, New York. De la Guardia was supposed to take close-up photographs of tangles of freshly made nanotubes, but he found that the flash from his camera ignited the fluffy masses. The researchers and their colleagues repeated the process with the tubes in a vacuum or surrounded by helium or argon gas. In those experiments, the tubes could not burn for lack of oxygen, but the light still scrambled the arrangement of the carbon atoms, the team reports in the 26 April issue of Science. The changes suggest that light might be used to control the properties of single-walled nanotubes, Ajayan says.
The fire-from-light phenomenon could also have direct applications, says David Carroll, a physicist at Clemson University in South Carolina. For instance, it might be used to control the ignition of flammable materials. "I anticipate a potential use in solid propellants such as the space shuttle's solid rocket motors," Carroll says. Michael Sailor, a materials chemist at the University of California, San Diego, says that the light-sensitive nanotubes might be used to set off minuscule "nano-explosives" to perform tiny remote-controlled chemical experiments, kill tumors from the inside out, or even power microscopic robots.