Exciton Relaxation in Carbon Nanotubes via Electronic-to-Vibrational Energy Transfer

Covalent functionalization of semiconducting single-wall carbon nanotubes (SWCNTs) can introduce new localized photoluminescent states that are strongly red-shifted from the emission commonly observed from the nanotube band-edge E₁₁ exciton state. In addition to being the source of new photophysical behaviors, these states are drawing significant interest as the basis for emerging functionality. A particularly important feature of such exciton localization at defect sites is that, because the exciton is no longer free to diffusively sample photoluminescent quenching sites along the length of the SWCNT, its lifetime is significantly extended.
We have recently demonstrated that an important recombination channel of such localized excitons is the electronic-to-vibrational energy transfer (EVET). This process is analogous to the Förster resonance energy transfer (FRET) except for the final state of this process is not electronically, but vibrationally excited molecules of the medium (e.g., solvent). In this talk we will discuss the basic physics of EVET and then proceed to estimating the EVET rate for a localized exciton in the SWCNT.