Length-dependent optical effects in single walled carbon nanotubes

Research areas:
  • Uncategorized
Year: 2008
Type of Publication: Article
  • Aruna Rajan, Daniel A. Heller Michael S. Strano
Journal: Journal of Physical Chemistry B Volume: 112
Number: 19 Pages: 6211-6213
Month: MAY 15 2008
PT: J; TC: 18; UT: WOS:000255649600040
Recently, Heller et al. reported length-dependent effects on the relative photoluminescence (PL) quantum yield of single walled carbon nanotubes (SWNTs) [Heller et al J. Am. Chem. Soc. 2004, 126, 14567-14573]. We propose a simple model involving thermal diffusion of excitons along the nanotube axis and quenching at the ends, to explain the observed trend in their data. By fitting to our model, we extract a diffusion coefficient of 6 cm(2)/s for excitons in SWNTs. Assuming a mono exponential decay of exciton PL, we also predict that effective length-dependent PL lifetimes for these excitons lie in the range of 1 - 27 ps. Experimental observations are shown to be consistent with stochastic rather than wavepacket-like exciton migration, which is in agreement with ultrafast excitonic dephasing. Edge effects seem to limit the use of short SWNTs in imaging and optical sensing applications.