Controllable expansion of single-walled carbon nanotube dispersions using density gradient ultracentrifugation

We present a protocol to selectively isolate single-walled carbon nanotubes (SWNTs) with different chiralities in a full-colored "rainbow" expansion using density gradient ultracentrifugation (DGU). Starting with SWNTs synthesized by the alcohol catalytic chemical vapor deposition (ACCVD) method, we used sodium deoxycholate (DOC) and sodium dodecyl sulfate (SDS) as cosurfactant encapsulating agents to form a DOC-restricted SDS wrapping morphology around the SWNTs. This enhances the density differences between nanotubes of different diameters, which leads to efficient chirality redistribution when combined with an appropriate density gradient profile. UV-vis-NIR absorbance spectra and photoluminescence excitation (PLE) maps show the optical properties of each fraction, and 97% pure isolation of (6,5) SWNTs achieved from the rainbow is also reported.