Tandem extraction strategy for separation of metallic and semiconducting SWCNTs using condensed benzenoid molecules: effects of molecular morphology and solvent.

Separation of metallic and semiconducting single-walled carbon nanotubes (SWCNTs) is of great importance for SWCNT-based nano-electronics. We propose a tandem extraction strategy for efficient separation of different types of SWCNTs. This strategy is based on chiral angle discriminated adsorption of soluble condensed benzenoid aromatic molecules on SWCNTs, which induce different dispersibility of SWCNTs in various organic solvents. The proposed tandem extraction strategy involves two extraction steps, in which the first step extracts metallic SWCNTs with large chiral angles and the subsequent step enriches large chiral angle semiconducting SWCNTs. This separation strategy is tested on a series of condensed benzenoid aromatic molecules. Both experimental and theoretical results show that the separation efficiency is strongly dependent on the molecular morphology, i.e. higher aspect ratio gives better separation results. The separation efficiency is also dependent on the SWCNT diameter and the solvent properties. This tandem extraction strategy may also be applied to other available noncovalent separation reagents to improve their separation efficiency.