Discovery of surfactants for metal/semiconductor separation of single-wall carbon nanotubes via high-throughput...

We report novel surfactants that can be used for the separation of metallic (M) and semiconducting (S) single-wall carbon nanotubes (SWCNTs). Among the M/S separation methods using surfactants in an aqueous solution, sodium dodecyl sulfate plays a key role in density gradient ultracentrifugation (DGU) and agarose gel separations. In this study, we screened 100 surfactants for M/S separation using a high-throughput screening system. We identified five surfactants, which could be used for both DGU and agarose gel separations, suggesting that the basic principle of these separations is common. These surfactants have relatively low dispersibilities, which is likely due to their common structural features, i.e., straight alkyl tails and charged head groups, and appeared to enable M- and S-SWCNTs to be distinguished and separated. These surfactants should stimulate research in this field and extend the application of electrically homogeneous SWCNTs not only for electronics but also for biology and medicine.