Length-Dependent Photoluminescence Lifetimes in Single-Walled Carbon Nanotubes

We describe the length-dependent exciton dynamics in DNA-wrapped single-walled carbon nanotubes (SWNTs) using time-resolved photoluminescence (PL) excitation correlation spectroscopy. We demonstrate that the effective PL lifetimes have substantial upper limits in longer SWNTs. Our results suggest that the exciton diffusion to the ends of the nanotube has only a limited contribution to the net nonradiative relaxation rate, and the nonradiative processes that occur before the excitons reach the ends of SWNT are the dominant contribution to the nonradiative lifetime. From the length-dependent PL lifetimes and relative intensities in DNA-wrapped SWNTs, the exciton diffusion length was found to be ∼50 nm, and the diffusion coefficient was ∼1 cm2/s.