Length separation of Zwitterion-functionalized single wall carbon nanotubes by GPC.

The length-fractionation of shortened (250 to 25 nm), zwitterion-functionalized, single wall carbon nanotubes (SWNTs) has been demonstrated via gel permeation chromatography (GPC). The UV-Vis spectrum of each fraction indicates an apparent "solubilization", as evident by the direct observation of all predicted optically allowed interband transitions between the mirror image spikes in the density of states of both metallic and semiconducting SWNTs with various tube diameters. As evident by the presence or absence of the 270 nm, pi-plasmon absorption, this "solubilization" is a dynamic process and leads to re-aggregation if left undisturbed for a couple of weeks or upon dissociation of the pendant octadecylamine groups. This non-destructive and highly versatile separation methodology opens up an array of possible applications for shortened SWNTs in nanostructured devices.