Hi there,
I'm working on a hydrophobic coating using the sol-gel method and I'm using TEOS (Tetraethoxysilane), FAS (perfluorooctyltrimethoxysilane), and OS (triethoxyoctylsilane) as precursors. In the XPS data, there were peaks at 286 eV and 288 eV in coatings with more FAS contents, which are related to C-O and C=O, respectively.
I think the peak at 286 eV is due to a partially hydrolyzed reaction of TEOS. However, I'm not sure why C=O has been detected. Can anybody help me with this?
Thank you.
C-C bond fixed at 286.5 eV and a small peak due to oxygen contamination. In spectra obtained from films containing fluorine, the contribution of C-O bonds is much smaller than that of C-F bonds. At the spectrum with 2 at.% fluorine, we already noticed the presence of a peak at 288.5 eV due to the C-CF bonds. The C-CF peak that appears in the spectra is due to a distortion in the C-C bond caused by a disturbance that the bonded fluorine
to the first carbon neighbour, which causes the C-C bond. The binding energy of a carbon atom bonded to another carbon atom is usually
observed at an energy of 284.5 eV, however, a fluorine atom in the vicinity of
one of these carbon atoms forming a C-F bond with an energy of 288.8
eV is capable of disturbing the second carbon atom, distorting the bonds
C-C.
Really we need to know what otehr elements are present and ideally see the spectra.
As it stands, I would suspect soem contamination, or more likely if any FAS remains from the synthesis, this could be 'secondary' shift of a carbon due to fluorine.
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