In the present study, we investigated the intermolecular
interactions
between single-walled carbon nanotubes (SWCNTs) and encapsulated molecules
by polarization resonance Raman microscopy. C70 encapsulated
in SWCNTs is investigated under incident laser polarization parallel
and perpendicular to the tube axis. We employed two excitation laser
wavelengths 442 and 532 nm, which are in resonance with different
electronic states of C70. Under 532 nm excitation, no distinct
polarization dependence is found in the Raman spectral pattern, while
under 442 nm excitation, a peak not previously seen for this excitation
wavelength was clearly observed for parallel excitation. This result
can be explained by the modulation of the resonance Raman process
via a charge transfer contribution between C70 and the
SWCNTs, which is sensitive to the incident polarization as well as
the excitation wavelength. The intensity of the local electronic field
inside a SWCNT is higher for the parallel excitation than the perpendicular
excitation when the nanotubes are in a bundle. The results can be
explained by field localization effects at the nanotube walls, qualitatively
supported by finite-difference time-domain simulations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.