Diameter-selective fractionation of HiPco single-walled carbon nanotubes in repeated functionalization reactions

The functionalization reaction of the diamine-terminated oligomeric poly(ethylene glycol) with a purified HiPco single-walled carbon nanotube sample was repeated multiple times to yield the corresponding number of soluble fractions and the final insoluble residue. According to results from the characterization with various instrumental techniques, these soluble fractions and the final residue all have different nanotube diameter distributions from that found in the starting sample. A general conclusion is that the functionalization and solubilization are selective toward smaller diameter nanotubes, regardless of their being semiconducting or metallic. Mechanistic implications, especially with respect to the post-production separation in terms of the nanotube metallicity, are discussed.