Page 111 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Nanomaterials Fabrication 97

the fluorinated (10,10) SWNTs with C F stoichiometry performed by
2
using DFT revealed 1,2 addition is more energetically preferable than
13
1,4 addition. Recently, solid-state C NMR has demonstrated the pre-
dominance of 1,2 addition and provided accurate quantification of the
C:F ratio [212]. F-SWNTs make highly flexible synthons and subse-
quent elaboration has been performed with organo lithium, Grignard
reagents, and amines [213–216].
Functionalized nanotubes can be characterized by a variety of
techniques, such as atomic force microscopy (AFM), transmission
electron microscopy (TEM), UV-vis spectroscopy, and Raman spec-
troscopy. Changes in the Raman spectrum of a nanotube sample can
indicate if functionalization has occurred. Pristine tubes exhibit two
1
distinct bands. They are the radial breathing mode (230 cm ) and
1
the tangential mode (1590 cm ) [217]. When functionalized, a new
1
band, called the disorder band, appears at approximately 1350 cm .
3
This band is attributed to sp -hybridized carbons in the tube.
Unfortunately, while the presence of a significant D mode is consis-
tent with sidewall functionalization, the relative intensity of D (dis-
1
order) mode versus the tangential G mode (1550–1600 cm ) is often
used as a measure of the level of substitution. However, it has been
shown that Raman is an unreliable method for determination of the
extent of functionalization since the relative intensity of the D band
is also a function of the substituents’ distribution as well as concen-
tration [215].

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