Covalent C-F bonds

In order to examine the chemical state on the carbon surface, x-ray photoelectron spectroscopy (XPS) analysis was performed for both the fluorinated carbon-coated AAO film and the liberated nanotubes from this fluorinated film. In the resulting XPS Cls spectrum of the fluorinated film (Figure 3.11a), the most intense component is the peak assigned to the covalent C-F bond (about 290eV),... 

The evolution of XPS spectra, given in Fig. 21 shows that the contribution of pristine non-functionalised C atoms remains majoritary, whatever the duration of the plasma treatment. The most noticeable change is the increase of the component (4) corresponding to covalent C—F bonds which are formed by the interaction of F radicals with the reactive sites of the material, i.e. surface defects, hydrogenated/oxygenated C atom, borders of the graphitic domains. When all these surface sites are fluorinated, the surface is saturated, what is accounted for by the value of C/F ratio of 3.2 obtained for t > 120 min [99],... 

Fluorination of natural graphite powder (x4 pm) by a gas mixture of F2, HF and IF5 yielded high fluorine content samples, CF0.8, CF0 9 and CF] 0 [34]. The structural parameters obtained by X-ray diffraction were 7C = 0.59 nm and oq = 0.246 nm. XPS data indicated the existence of two Cls peaks at 287.0 eV and 289.4 eV, and one F]S peak at 688.0 eV, which are intermediate values between those for semi-ionic and covalent C—F bonds. Galvanostatic discharge of these CFV samples was done... 

The molecule contains a carbon atom, two chlorine atoms, and two fluorine atoms. There are two covalent C-Cl bonds and two covalent C-F bonds. The Cl and F atoms have three lone pairs each. 

Covalent C—F bonds are also detectable in lamellar n charge-transfer graphite compounds such as CjSbFj C KrFj and halogen fluorides (see 16.4.2.1.1 and reviews ). These mixed covalent-rr charge-transfer compounds arise from internal fluorination by the intercalant. 

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