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

The purpose of manipulating isolated single-wall carbon nanotubes (SWNTs), rather than bundles, has led to an 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 functionalisation degree, it is important to develop reliable and simple methods to quantify this degree. The C n F stoichiometry of three different fluorinated SWNTs samples are determined with the X-Ray Photoelectron Spectroscopy (XPS). Then the evolution of the Raman spectra with the fluorination degree 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.