Photoluminescence and Forster Resonance Energy Transfer in Elemental Bundles of Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) are commonly synthesized in bundles for which the luminescence is often quenched altogether. Here, we report on the simplest case of nanotube bundles: a single pair of individual air-suspended SWNTs. Using luminescence imaging spectroscopy, we find that emission and excitation spectra can be described within an energy transfer picture, with donor to acceptor transfer of excitation. The multiplicity of emission peaks in small bundles indicates that the transfer of luminescence is only partial at room temperature, with thermal occupation of the donor being significant. We attribute this signature to the unique band structure of SWNTs, with diameter and chirality dependent energy, recombination rate, and density of states.