Dateline: June 6, 2001

The study of synthetic one dimensional [1] structures has proven to be an especially productive branch of nanoscience. The importance of one dimensional objects can be seen in biomolecular nanotechnology [2], which uses linear molecules for everything from informatics [3] to transportation [4] - all on the nanoscale, of course. Molecular cylinders known as nanotubes [5] have been found to be a particularly stable organization of elements [6]. Carbon nanotubes were the first to be discovered [7], and the discovery of inorganic nanotubes followed soon after [8]. Carbon nanotubes are the most well studied of the synthetic nanotubes. Their electronic properties [9] have been thoroughly examined, and single crystals of pure carbon nanotubes have been formed by self-assembly [10].

In a remarkable feat of atomic precision, Remskar et. al. has reported the synthesis of single-wall molybdenum disulfide nanotubes [11]. During the synthesis, the tubes self-assemble into regular geometric shapes, exhibiting self-organization on scales all the way from the bottom up to the milli-scale. The synthesis was found to require the presence of buckyballs (C₆₀). While the exact growth mechanism is not known, the C₆₀ is not present in the final product. Thus, C₆₀ seems to function as a catalyst, presumably allowing growth at the tips of the tubes. On the nanoscale, the tubes self-asemble into hexagonally packed bundles, with iodine atoms organized one dimensionally between three adjacent tubes.

These nanotubes are extraodinarily small, with the diameter being less than one nanometer. Theory has predicted the stability of large diameter molybdenum disulfide nanotubes, which are expected to be semiconducting. Because these tubes are much smaller, extrapolations of those calculations predicts that these tubes should be conducting, with persistent quantization for electrons hopping perpendicular to the tube axis. Such quantum behavior is what makes low dimensional materials so unique, allowing discrete energy coupling [12] and making quantum engineering [13] a newly emerging discipline.