Swnt-Sorting with a Removable Solubilizer Based on Dynamic Supramolecular Coordination Chemistry

Abstract

Highly pure semiconducting single-walled carbon nanotubes (SWNTs) are essential for the next generation of electronic devices, such as field-effect transistors and photovoltaic applications, but contamination by metallic-SWNTs reduces the efficiency of their associated devices. Polyfluorene-based copolymers (PFOs)1, 2 have been intensively studied because they dissolve/extract only sem-SWNTs in toluene by a simple sonication method. We have previously demonstrated a rational method for the selective extraction of a specific chirality of the sem-(n,m) SWNTs using a series of systematically designed fluorene-based copolymers3-4. Moreover, we revealed that the PFO copolymers with a bulky optically active moiety could separate the right- and left-handed sem-SWNTs5. However, there are several serious problems when using PFOs; that is, difficulty in the removal of the wrapped PFOs from the SWNTs/PFO composites6, 7 as well as their low extraction efficiency from the as-produced SWNTs1, 2. Here we report a simple and efficient method for the separation of semiconducting- and metallic-SWNTs based on supramolecular complex chemistry.8 We describe the synthesis of metal-coordination polymers (CP-M) composed of a fluorene-bridged bisphenanthroline ligand and metal ions. Based on a difference in the ‘solubility product’ of CP-M-solubilized semiconducting-SWNTs and metallic-SWNTs, we readily separated semiconducting-SWNTs. Furthermore, the CP-M polymers on the SWNTs were simply removed by adding a protic acid and inducing depolymerization to the monomer components. We also carried out molecular mechanics calculations to reveal the difference of binding and wrapping mode between CP-M/semiconducting-SWNTs and CP-M/metallic-SWNTs. This study opens a new stage for the use of such highly pure semiconducting-SWNTs in many possible applications.