Carbon Nanotube; http://www.flickr.com/photos/ghutchis/ / CC BY-ND 2.0 |
 |
Imagine a tiny tube. Now imagine it even tinier than that — so tiny that not even a single molecule of caffeine can pass through it. Carbon nanotubes, some only fractions of a nanometer (one billionth of a meter) in diameter, consist of seamless graphite layers shaped in cylinders with one capped end that can extend several centimeters.
Discovered accidentally in 1991 by Sumio Iijima, carbon nanotubes, despite their small size, have the strongest tensile strength of any known material. Their extremely high thermal conductivity, electrical superconductivity, precise positioning of atoms, light weight, and potential for molecular transport provide numerous applications in electronics, aerospace, and medicine. They may even be used for the construction of space elevators, providing material for the cable to move things between Earth and space. (Not humans, though, unless we do something about that nasty space radiation.) In the US, the potential of carbon nanotubes was recognized in 2001 with the establishment of the National Nanotechnology Initiative program.
Carbon nanotubes can have single or multiple walls. Single walled tubes have higher thermal conductivity and more desirable electrical properties for use in electronics and heat transport. Multiwalled tubes have potential as biosensors in medicine and laboratory science used to detect microscopic amounts of chemical or biological compounds. Nanotubes have potential in drug delivery and targeted treatment, although studies have shown nanotubes to be toxic in mice if they reach the lungs.
NASA Goddard Photostream; Image credit: Yuki Kimura, Tohoku University |
|
With the immense interest in carbon nanotubes, a revolution of sorts in industry has occurred. The synthesis of carbon nanotubes generally requires the use of a cobalt or nickel catalyst. But most recently, Joseph Nuth of NASA Goddard in Greenbelt and colleagues described a new form of nanotube synthesis in Astrophysical Journal Letters that results from the recycling of carbon in space when supernovas explode. Instead of requiring a metal catalyst, a mass of nanotubes were produced when graphite dust particles were exposed to a mixture of carbon monoxide and hydrogen gases (using a known method for making liquid fuel from coal). This research was spawned by the discovery of graphite whiskers, large carbon nanotubes, that were found associated with meteorites. If this new form of synthesis can result in lightweight and orderly tubes, it may mean an innovation for the nanotube industry.
In addition, the formation of these large nanotubes may be the reason supernovas appear dimmer than we expect from their distance alone. Imagine that: A nanotube-haze in space.
Read an article in the Baltimore Sun on Nanotechnology here.
