OVERVIEW ON THE MAJOR RESEARCH ACTIVITIES ON CARBON NANOTUBES BEING DONE IN AMERICA, EUROPE AND ASIA - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 310

in nature. On the other hand, the nanotube ield restricts the centre of mass
position of the fullerenes on a 1D chain along the nanotube axis, which means
that the molecular orientation of these molecules is inluenced by neighboring
C 60 -C 60 interactions, so that these molecules can statistically adopt a large
number of orientations. At low temperature, however, the potential barrier
that a C 60 has to overcome to change from one orientation to another becomes
non-negligible.
Figure 9.38 Left : Raman spectra for Ce@DWCNTs (A), CeCp 3 @SWCNTs (B), and
their difference (A-B) at the radial breathing mode region. Right : TEM micrographs
of CeCp 3 @SWCNT ( top ) and Ce@DWCNT ( middle and bottom ). Scale bar = 1 nm.
Reprinted with permission from Shiozawa et al . 220 Copyright (2009) by the American
Physical Society. See also Colour Insert.
Because of their excellent structural and chemical integrity, CNTs also
provide an ideal 1D environment to explore chemistry at the nanoscale. To
that purpose, the researchers have doped SWCNTs with tris(cyclopentadie
nyl)cerium (CeCp 3 ) through van Hove singularity (VHS), which has shown
the ability to modulate the conductivity of SWCNTs. 220 In more details, the
left-hand panel of Fig. 9.38 shows the Raman spectra of a CeCp 3 @SWCNT
sample before and after annealing at 1000 ° C in vacuum. Both spectra contain
the expected radial breathing modes of pristine tubes at frequencies ranging