ja5b13496_si_004.mpg (6.54 MB)
Fullerene-Assisted Photoinduced Charge Transfer of Single-Walled Carbon Nanotubes through a Flavin Helix
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posted on 2016-04-29, 13:09 authored by Mehdi Mollahosseini, Erandika Karunaratne, George
N. Gibson, Jose A. Gascón, Fotios PapadimitrakopoulosOne
of the greatest challenges with single-walled carbon nanotube
(SWNT) photovoltaics and nanostructured devices is maintaining the
nanotubes in their pristine state (i.e., devoid of aggregation and
inhomogeneous doping) so that their unique spectroscopic and transport
characteristics are preserved. To this effect, we report on the synthesis
and self-assembly of a C60-functionalized flavin (FC60), composed of PCBM and isoalloxazine moieties attached on
either ends of a linear, C-12 aliphatic spacer. Small amounts of FC60 (up to 3 molar %) were shown to coassembly with an organic
soluble derivative of flavin (FC12) around SWNTs and impart effective
dispersion and individualization. A key annealing step was necessary
to perfect the isoalloxazine helix and expel the C60 moiety
away from the nanotubes. Steady-state and transient absorption spectroscopy
illustrate that 1% or higher incorporation of FC60 allows
for an effective photoinduced charge transfer quenching of the encased
SWNTs through the seamless helical encase. This is enabled via the
direct π–π overlap between the graphene sidewalls,
isoalloxazine helix, and the C60 cage that facilitates
SWNT exciton dissociation and electron transfer to the PCBM moiety.
Atomistic molecular simulations indicate that the stability of the
complex originates from enhanced van der Waals interactions of the
flexible spacer wrapped around the fullerene that brings the C60 in π–π overlap with the isoalloxazine
helix. The remarkable spectral purity (in terms of narrow ESii line widths)
for the resulting ground-state complex signals a new class of highly
organized supramolecular nanotube architecture with profound importance
for advanced nanostructured devices.