posted on 2016-05-16, 00:00authored byRandy
D. Mehlenbacher, Jialiang Wang, Nicholas M. Kearns, Matthew J. Shea, Jessica T. Flach, Thomas
J. McDonough, Meng-Yin Wu, Michael S. Arnold, Martin T. Zanni
We
observe ultrafast energy transfer between bare carbon nanotubes
in a thin film using two-dimensional (2D) white-light spectroscopy.
Using aqueous two-phase separation, semiconducting carbon nanotubes
are purified from their metallic counterparts and condensed into a
10 nm thin film with no residual surfactant. Cross peak intensities
put the time scale for energy transfer at <60 fs, and 2D anisotropy
measurements determine that energy transfer is most efficient between
parallel nanotubes, thus favoring directional energy flow. Lifetimes
are about 300 fs. Thus, these results are in sharp contrast to thin
films prepared from nanotubes that are wrapped by polymers, which
exhibit picosecond energy transfer and randomize the direction of
energy flow. Ultrafast energy flow and directionality are exciting
properties for next-generation photovoltaics, photodetectors, and
other devices.