A spectroscopic study of the fluorination and defluorination reactions on single-walled carbon nanotubes

The manipulation of isolated single-wall carbon nanotubes (SWNTs), rather than bundles, has led to active research in the field of the functionalisation of such carbon compounds. Different ways exist today to obtain some new soluble macromolecules from SWNTs. Here we focus on the fluorination functionalisation. As the solubility properties depend essentially on the degree of functionalisation, it is important to develop reliable and simple methods to quantify this. The CnF stoichiometry of three different fluorinated SWNTs samples are determined with X-ray photoelectron spectroscopy (XPS). Then the evolution of the Raman spectra with the degree of fluorination of these samples is discussed. An atomic force microscopy (AFM) study highlights the good solvation properties of the most fluorinated sample with a majority of isolated nanotubes being observed. Then we take advantage of these good solvation properties, combined with the possibility of recovering the pristine non-fluorinated nanotubes, to carry out surface enhanced Raman spectroscopy (SERS) studies of well-dispersed SWNTs. These studies put in evidence the bundle effect, which is due to the agglomeration of SWNTs into bundles. This effect can be readily observed by Raman spectroscopy.