Ultrafast Exciton Energy Transfer in Bundles of Single-Walled Carbon Nanotubes

Excitation energy transfer is a long-lasting issue in the fields of photoscience and materials science encompassing physics, chemistry and biology. We report femtosecond energy transfer of quasi-one dimensional excitons in single-walled carbon nanotube bundles, when we investigate using time resolved luminescence spectroscopy Luminescence decay times are found to increase with decreasing photon energy from 1.2 to 0.6 ev. The energy-dependent decay behaviour is analyzed using a simple rate equation based on the measured diameter distribution of the tubes. The rate of exciton energy transfer per nanotube from an excited semiconducting tube to adjacent metallic tubes [1.8 x 1.9 x 0.2) x 10(12) s(-1)] is 16 times that of transfer to adjacent metallic tubes [(1.1 +/- 0.2) x 10(-12) s(-1)]. The observed transfer rates are much lower than those predicted by the Forster model. This finding provides insight into the energy transfer mechanisms of one dimensional excitons.