Researchers get a handle on carbon nanotubes
Announcements about carbon nanotubes seem to be nearly as abundant as carbon itself these days, but most gloss over a fundamental challenge: These nanotubes—cylindrical carbon molecules 50,000 times thinner than a human hair—are devilishly difficult to manipulate. Noting that a batch of nanotubes is more likely to resemble a bowl of spaghetti than a circuit or any other useful structure, a group of researchers at the Massachusetts Institute of Technology has developed a way of attaching molecular "handles" to the sides of the nanotubes.
Others have accomplished similar feats, but the MIT team claims that its handles are the first to afford control over nanotubes without reducing their near-perfect conductivity. Like fuzzy balls and Velcro, the hexagon of carbon that makes up a nanotube has a predeliction for clinging to other hexagons. The researchers identified carbenes and nitrenes that not only provide a grip on the nanotubes, but also prevent them from sticking to each other—a serious problem with the gregarious, hexagonal structures.
The MIT scientists also report that some of their handles can transform from a bond-intact to a bond-broken state, which may provide the ability to switch the nanotubes' conductivity on or off in the presence of certain substances or a laser beam. "This direct control of conductance may lead to novel strategies for the manipulation and assembly of nanotubes in metallic interconnects or to sensing or imaging devices that respond in real time to optical or chemical stimuli," says Nicola Mazari, an associate professor in the materials-science and -engineering department at MIT, who, along with Young-Su Lee, a graduate student in the same department, led the study. This method of control may propel nanotubes into useful applications in interconnect, chemical detectors, and image sensors, according to MIT.