Separation of metallic and semiconducting single-walled carbon nanotubes via covalent functionatization

The advancements made in the field of single-walled carbon nanotubes (SWNT) using the covalent chemical functionalization techniques are presented. Several methods have been investigated in order to separate metallic from semiconducting tubes, which can be divided into three categories. The categories include, selective destruction of one type of nanotube, physical techniques, and covalent functionalization. The most useful technique to determine whether a mixture contains met-SWNTs or sem-SWNTs are Raman scattering and UV/Vis-near infrared spectrophotometry. Absorption spectra displays the transitions between the van Hove singularities of the density of state (DOS), which are characteristic of one dimensional system. This method is expensive due to the cost of synthetic DNA but the broad range of possibilities offered by DNA in terms of self-assembly may lead to fine tuning of the separations.