Biomedical Engineering Reference
In-Depth Information
(VV)
(VH)
200
(a)
(b)
0
20
40
60
100
100
80
120
140
160
180
0
1500
1575
1500
1575
1650
Frequency (cm 1 )
(c)
(d)
20
10
0
0
60
120
180
0
60
120
180
()
()
FIGURE 15.20 Polarization dependence of the G band from one isolated semiconducting SWNT sitting
on an Si/SiO 2 substrate with incident and scattered light parallel (a) and crossed (b) to each other. φ
stands for incident light polarized along the nanotube axis. Points on (c) and (d) plot the G band intensity
dependence on φ for (a) and (b), respectively. The solid curves fi t the data points with the functions cos 4 (φ)
and cos 2 (φ) sin 2 (φ). (Reprinted with permission from [137]. Copyright (2002) American Physical Society.)
Khare et al. [141] functionalized single-walled carbon nanotubes through a micro-
wave discharge of ammonia. SWNTs exposed to both NH 3 and ND 3 discharges display
RBM frequency shifts from that of the pristine nanotubes (Fig. 15.22) since sidewall
functionalization of the nanotubes results in a general increase of CNT diameter. The
frequency of the G band (1594 cm 1 in pristine SWNT) also shifts toward the lower
energy (1583 cm 1 ) in the NH 3 functionalized SWNT, and the line shape is broadened.
This change in G band frequency further suggests the sidewall interactions with NH
species.
In another example [56] SWNT was modifi ed with peroxytrifl uoroacetic acid
(PTFAA). Raman spectrum of the carbon nanotubes after the PTFAA treatment
shows a D-line substantially increased indicating the formation of “defect” sites with
sp 3 -hybridized carbon atoms on the sidewalls due to the addition of the functional
groups. The RBM bands in the region of 170-270 cm 1 decreased and shifted to higher
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