Bright Luminescence and Exciton Energy Transfer in Polymer-Wrapped Single-Walled Carbon Nanotube Bundles

Selective solubilization of semiconducting single-walled carbon nanotubes (SWNTs) by polymer wrapping leads to bright luminescence even in bundles because of suppression of deexcitation processes via metallic SWNTs. We investigate photoluminescence (PL) properties of polymer-wrapped SWNTs in a paper form by means of PL excitation spectroscopy and time-resolved PL spectroscopy PL excitation spectra indicate bright luminescence and the existence of exciton energy transfer from wide to narrow gap tubes. Time-resolved measurements show that the luminescence decay becomes slower with decreasing gap energy. The observed decay behaviour is analyzed by a simpler rate equation model describing both intratube exciton decay and exciton energy transfer to neighbouring tubes. It is found that the intratube exciton decay rate and the effective transfer rate per tube at the center to center distance of similar to 1.9 nm are 1.1 x 10(11) s(-1) and 2.7 x 10(11) s(-1) respectively. These findings are relevant for understanding of energy transfer mechanisms of one-dimensional excitons.