Carbon Nanowire (CNW)

CARBON NANOWIRE (CNW), a one-dimensional string of carbon atoms threaded through a carbon nanotube, has been observed for the first time. Carbon chains have been observed before, but never inside a nanotube. Yosinori Ando and his colleagues at Nagoya University (Japan) produced the CNWs amid a welter of nanotube whiskers by shooting an electrical arc between two carbon electrodes, and employ not the usual helium atmosphere but one of hydrogen. (This same team has produced the smallest nanotubes---only 0.4 nm in diameter---and multiwalled nanotubes with the thinnest inner diameter---only 1 nm.) Carbon nanowires should have interesting mechanical properties; e.g., as ultrastrong fibers they might serve in Space Shuttle nosecones or as friction-free rotational bearings (see PNG figure). Their chemistry is also new. The allotropes of carbon are usually classified according to the type of chemical bonding, whether of the "s" type (the electron residing in a spherical orbital cloud) or the "p" type (dumbbell shaped orbital). The three known carbon bondings are sp³ (diamond), sp² (graphite, fullerene, and nanotubes), and sp (carbon chain). The CNW allotrope, however, partakes of both the sp and sp² bondings. In the electronic realm, CNWs might provide the smallest possible metal-metal junction, or provide highly coherent point sources of mono-energetic electron beams. Finally, CNWs provide a quick way to study 1-dimension carbon chains, which might account for some of the mysterious emissions from interstellar space. (Zhao et al., Physical Review Letters, 5 May 2003; contact Yoshinori Ando, 81-52-832-1151, x5280; visit the website for more information)