Dependence of Exciton Mobility on Structure in Single-Walled Carbon Nanotubes

Optically generated excitons in semiconducting single-walled carbon nanotubes (SWCNTs) display substantial diffusional mobility. This property allows excitons to encounter similar to 10(4) carbon atoms during their lifetime and accounts for their efficient deactivation by sparse quenching sites. We report here experimental determinations of the mobilities of optically generated excitons in 10 different (n,m) species of semiconducting SWCNTs. Exciton diffusional ranges were deduced from measurements of stepwise photoluminescence quenching in selected individual SWCNTs coated with sodium deoxycholate surfactant and immobilized in agarose gel. A refined data analysis method deduced mean exciton ranges from 190 to 370 nm. The results suggest that exciton range increases weakly with nanotube diameter over the 0.7-1.2 nm diameter range and that species with near-armchair roll-up angles have the smallest exciton ranges. No significant correlation was found between the exciton range and measured photoluminescence action cross section, which represents fluorimetric brightness. These findings highlight the importance of complementary photophysical studies to elucidate factors controlling SWCNT exciton mobility