Single-walled carbon nanotubes (SWCNTs) are formed, at least theoretically, by rolling a single-layer graphene sheet once.  Depending on how the graphene sheet is oriented with respect to the central axis, the nanotube can be a semiconductor or metal.  Often, SWCNTs are considered to be be one dimensional, with diameters that are 1 nm and lengths ranging from 100 nm to 10 microns.

Figure 1:  (a) Picture of enriched nanotube solutions.  The purple solution is highly enriched in semiconductors, while the two yellowish vials are metallic. (b) Absorption spectra of an 'as-produced' SWCNT solution (black) and a single-chirality, metallic nanotube solution (red).

Our current interest with SWCNTs is to explore the optical and electrical properties of  metallic nanotubes.  Working with collaborators at NIST, we hope to achieve highly aligned and single chiral-enriched metallic SWCNTs to avoid contamination and spurious effects from semiconducting nanotubes.  Once a single-chirality metallic sample can be produced, we will align the nanotubes along a common axis for optical and electrical measurements, such as transient absorption and temperature-dependent magneto-resistance.