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 273

Figure 9.19. (a) Functionalisation of surfactant-wrapped SWCNTs by addition of
4-substituted benzenediazonium salts at basic pH. (b) Diazoanhydride formation.
Figure modiied from Doyle et al . 116 with permission.
Another method has made use of aryl diazonium salts to introduce
repetitive functionalisations for multifunctional SWCNTs. 117 The obtained
products displayed enhanced water solubility and provided a protective
environment towards those molecules that, otherwise, would not be very
stable. The bulky assembles were characterised using Raman spectroscopy,
thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy
(XPS).
Covalent functionalisation of the nanotube sidewall has been achieved
through the partial substitution of luorine in luoro-CNTs (F-SWCNTs) by
other moieties, including urea, guanidine and thiourea ( Fig. 9.20) . 118 The
successful functionalisation has been conirmed by several techniques,
including Raman spectroscopy, Fourier transform IR (FTIR), TGA, scanning
electron microscopy (SEM), XPS, transmission electron microscopy (TEM)
and AFM. F-SWCNTs have been also characterised by magic angle spinning 13 C
NMR spectroscopy, 119 from which an interesting conclusion could be derived:
where a comparison of samples with a high degree of functionalisation is
required, NMR provides a much better quantiication than Raman. However,
where a comparison between samples with low levels of functionalisation or
large differences in degree of functionalisation is required, Raman provides a
much better quantiication than NMR.