I have XPS spectra of oxyfluorinated graphene and a reference graphene. The wide scans clearly indicate the presence of fluorine and the narrow scans show clear covalent bonding energy between 687 and 688 eV. The fluorine content of the oxyfluorinated graphene shows a 4at% content. However, the C1 narrow scan appears to be one peak (284.58 eV) with almost no shoulder. The deconvolution indicates peaks at 285.1 eV and 286.48 eV. Could this be CCF and C=O bonds as I'm struggling to clearly identify these peaks from literature? My suspicion is that the 286.48 may be CCF bond which is in that region. This peak is very small in comparison with the other deconvoluted peaks for the C1 scan. Any help would be appreciated.
Hi
Usually, C-F binding energy appears at ~290 eV in C1s spectra. Look at this article (J. Mater. Chem. A, 2014,2, 8782-8789).
As noted, peaks for -CF- and -CF2- appear around 290. Your scan does not go to high enough binding energy to see these species. The peak at 286.4 could be from -C-CF2-. However, you would then expect a peak for the -CF2- as well. Until you find a -CF- or -CF2- peak, you cannot assign a -C-CF2- peak.
I might also caution that your peak fitting (NOT deconvolution -- that is something else entirely) could just as well be done with only two peaks rather than three. The shoulder at higher binding energy could be an artifact that is due to using an incorrect baseline function (use a Shirley or Tougaard not a linear baseline). Or it could be that you are fitting data that are distorted because they were overly smoothed (peak fitting should be done to the raw data, not smoothed data).
In other words ...
Based on the plot you show, the peak at 286.4 is certainly not yet proven to be -C-CF2-, and I do not yet trust the significance of having this peak in any case.
Hi Louis,
I've attached the spectra of the first fully flourinated graphene. The blue trace is total and the red is partial. However, from experience, I can tell you that these peaks don't 'pop out' at you until after 10% fluorination. Yours looks like the peak broadening I saw with our experiments. Unfortunately, all the broadening shows is that there is a change in the carbon's physical state, which could be due to more factors than simple fluorination. Long story short, I'm not sure if XPS is an appropriate tool below 20% C-F concentration.
Dear colleagues,
Thank you for the valuable input and my concern was also that the peaks at 290 didn't appear. It seems that my oxyfluorination concentration is just too low to generate the appropriate peaks. I will try different concentrations and inform you if other peaks appear then. Nonetheless, with the low concentration I did manage to improve certain properties of my composites.
Kind regards and thank you again
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