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 302

hand, Cs + ions migrate randomly on the outer nanotube wall, without retaining
their position for more than 2 seconds. Conversely, they were trapped at
defective parts of the nanotubes (Fig. 9.33).
Figure 9.33 Images of C 60 nanopeapods after doping with cesium OUTSIDE. Cs + ions
trapped at the defects in the nanotubes are indicated by blue triangles, and that of the
defect-free part of the nanotube wall is indicated by a red triangle. Reproduced with
permission from Sato et al . 199 See also Colour Insert.
Ask for copyright permission to Sato, Yuta; Suenaga, Kazu; Bandow, Shunji;
Iijima, Sumio. Site-dependent migration behavior of individual cesium ions
inside and outside C 60 fullerene nanopeapods. Small, 2008, 4(8), 1080-1083.
It has been repeatedly demonstrated that C 60 fullerenes can be
encapsulated in SWCNTs to form a 1D hybrid nanostructure, the so-called
carbon nanopeapods. 201 However, the coalescence of C 60 molecules assisted
by intratubular doped iodine atom(s) inside SWCNTs has been much
less investigated. The research group has adopted HR-TEM and Raman
spectroscopy to demonstrate that the doped iodine atoms (even one atom!)
can induce the structure transformation of C 60 fullerenes inside SWCNTs. 202
The C 60 peapods were immersed in molten iodine in an evacuated glass tube
at 150°C over 24 hours for doping, after which some dark spots appeared,
presumably attributable to iodine (Fig. 9.34). It seemed that SWCNTs with
diameter larger than 1.6 nm could accommodate the iodine molecules,
although in an inhomogeneous way. In order to verify that C 60 's transformation
into tubular shape was induced by iodine, both intact C 60 peapods and their
iodine-doped counterparts were incubated for 24 hours at 550°C, which
represents a value below the reported minimum coalescence temperature
(800°C) of the intact C 60 @SWCNTs. As expected, in the case of the iodine-
doped samples, a prominent structure transformation was revealed by the
Raman spectra and HR-TEM observation (Fig. 9.35).