Photoluminescence from Exciton Energy Transfer of Single-Walled Carbon Nanotube Bundles Dispersed in Ionic Liquids

Single-walled carbon nanotubes (SWNTs) can be dispersed into fine bundles in imidazolium-based ionic liquids (ILs) by simple mechanical grinding. Photoluminescence (PL) of the exciton energy migration from larger band gap semiconducting donor nanotubes to smaller band gap semiconducting acceptor nanotubes within the same SWNT bundle is clearly observed and can be explained by the Förster resonance energy transfer (FRET) mechanism. This offers a simple way to relatively brighten up the PL of those less populated, large diameter, small band gap SWNT species. Taking surfactant sodium dodecyl sulfate (SDS)-dispersed samples as a control of individually dispersed SWNTs, incomplete thermalization before exciton recombination is demonstrated in IL-dispersed SWNT bundles.