Facile and Effective Post-Production Separation of Single-Walled Carbon Nanotubes with Paired Aromatic Molecules: A Molecular Tweezers Approach

Abstract

As-produced single-walled carbon nanotubes (SWNTs) are mostly metallic and semiconducting mixtures. The population of semiconducting SWNTs in the as-produced mixtures is generally much higher than that of their metallic counterparts. Therefore, postproduction separation of metallic and semiconducting SWNTs is important to many potential uses of the nanotubes, especially those demanding higher electrical conductivity yet lower optical absorption. Because planar aromatic species are known to have somewhat different interactions with metallic and semiconducting SWNTs, in this work a molecule with a pair of planar aromatic moieties was specifically designed and synthesized to exaggerate the difference in its noncovalent functionalization and solubilization of the two types of nanotubes. As demonstrated, the molecule exhibited significant selectivity toward semiconducting SWNTs in the solubilization to allow the convenient harvesting of bulk metallic and semiconducting fractions in high purities. The results suggest that molecules with paired aromatic species or essentially molecular tweezers may represent a new class of agents for more effective and also relatively simple postproduction bulk separation of metallic and semiconducting SWNTs.