Biomedical Engineering Reference
In-Depth Information
Besides fullerenes, other molecules have been encapsulated inside
CNTs: an interesting example is provided by the self-assembly of SiO
2
-based
nanomaterial inside single- and double-walled CNTs.
198
Once again, tubes'
diameter played a crucial role, by inluencing the inal structure of the
original cubic octameric H
8
Si
8
O
12
molecules formed inside the CNTs: in case
of CNTs having inner diameters of 1.2-1.4 nm, a new ordered self-assembled
structure composed of H
8
Si
4
n
O
8
n
−4
molecules was formed, while for tubes
larger than 1.7 nm, a disordered structure originated inside the tubes. Such
result was conirmed by high-resolution transmission electron microscopy
(HR-TEM), FT-IR spectroscopy and Raman spectroscopy, suggesting strong
interactions occurring between CNTs and H
8
Si
4
n
O
8
n
−4
molecules.
In another study, the research group investigated the migration of
individual cesium ions (Cs
+
) both inside and outside C
60
nanopeapods.
199
Cs
+
ions inside the nanopeapods were detected as dark dots inside tubes of
about 1.5 nm, but not in the inner wall of SWCNTs of 1.38
±
0.03 nm. It was
suggested that these tubes were too small to accommodate the migration of
Cs
+
ions, while smaller K
+
ions were already demonstrated to be internalised
inside tubes of 1.4 nm.
200
TEM images showed an ordered Cs
2
C
60
structure
with planar Cs
+
coniguration in which each C
60
cage was adjacent to four Cs
+
ions (Fig. 9.32).
(a)
(b)
Figure 9.32
(a)
TEM images of C
60
nanopeapods after doping with cesium INSIDE.
(b) Schematic illustration of the ordered Cs
2
C
60
structure inside a SWCNT (
right
) and
its simulated TEM image (
left
). Reproduced from Sato
et al
.
199
with permission. See
also Colour Insert.
Sequential TEM images of these samples indicated that Cs
+
ions were
inluenced by the deformation of the tubes, which luctuated between 1.44
and 1.56
±
0.03 nm due to elastic deformation during the TEM. On the other
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