Wide scan spectrum of a fully aromatic polyamide surface shows the presence of 15.7% Oxygen, 9.2% Nitrogen and 75.1 % carbon.
According to my experiment, I expect to have 3 functional groups in my sample.
1. Carboxylic Acid (O=C-OH)
2. Amid (O=C-N)
3. Anhydride (O=C-O-C=O)
I want to determine the availability and percentage of 3 mentioned functional groups by curve fitting of O 1s high resolution XPS spectrum which is attached. It should be noted that in the amide functional group, for each N atom, there is one O atom. So, 58.59% of total recorded Oxygen atoms relate to amide molecules (9.2 0f 15.7 ) and others can relate to acid and anhydride groups.
Would you mind helping me to solve this problem?
Thanks in advanced
Regards
It is always hard to fit O1s spectra - this is because the chemical shifts between the different C-O bonds are extremely small. And, in your specific case, you have contributions from different groups with the same ligands to the oxygen. I would rather try to fit two species to the oxygen, i.e. a single peak for C=O and a second for C-O-C, and a third species for the OH-groups. Check it out and see what happens numerically. It would also be an idea to fit the C1s spectra consistently ... good luck, Dirk
Dear Dirk
I have tried to fit oxygen peak by these three groups, but results didn't confirm the wide-scan results (58.59% of total recorded Oxygen atoms relate to amide group). However, do you know binding energy shift for the three mentioned Oxygen groups? I
Besides, I think the C1s binding energies for amide (O=C-N), acid (O=C-O) and Anhydride (O=C-O-C=O) groups are the same.
Thanks
In fact, your sample represents a difficult situation, the C1s binding energies for amide (O=C-N), acid (O=C-O) and anhydride (O=C-O-C=O) may be almost idential. Do you have any clean references for modelling these orbitals SEPARATELY? Then you may transfer the results to your "mixed" sample ...
Only as a first and rough approximation to the problem, you may fit the O1s peak to two components.
1) The low binding energy component (LBE) attributed to C=O groups
2) The high binding energy component (HBE) to attributed to C-O groups
As commented previously by Prof. Dirk, it would be interesting to fit the C1s peak. As a starting point you may use four components:
1) At 285.0 eV the component attributed to C-C/C-H groups
2) At about 286.0-286.5.eV the component attributed to C-NH/C-O groups
3) At about 288.0 eV, the component attributed to N-C=O groups.
4) At about 289.0eV the component attributed to OH-C=O groups
From the atomic percentages of the elements and the percentages of area of the components you may obtain and compare the atomic percentages of the different chemical species. For example the atomic percentage of N may be related with the percentage of N-C=O or C-NH groups from the fitting of the C1s peak
Dear S. Feliu Jr,
Thank you for your reply.
However, I think 288.0 eV binding energy in addition to O-C=O, is relative to N-C=O. On the other hand, I cant find the concentration of Anhydride group (O=C-O-C=O) in my sample by the mentioned binding energies. My major problem is to find a binding energy for C-O-C species. Does oxygen in C-OH and C-O-C have the same binding energy?!!
Best regard,
Dear Hossein:
Thank you for your answer
The LBE component of the O1s peak may correspond to the carboxylic oxygen (C=O) and the HBE component to singly bonded oxygen (C-OH or C-O-C).
Best regards
Try the NIST data base, or alternatively lasurface.com
Kind regards, Dirk
Hello,
Please check the following link www.xpsfitting.com/search/label/Oxygen. This blog has a pretty good answer to your question.
Take care,
Rafal
Hossein Karimi Deconvolution of a composite peak into its individual peaks plays an important role in the interpretation of many types of graphs including XRD, XPS, FTIR, and PL etc. In this video, I have discussed how to deconvolute simple combined peaks, composite peaks and how to correct missing data in a given peak with the help of deconvolution. In the case you want to further ask about it, please do comment on the specific video, I'll respond to it shortly. I have provided the practice filee (OriginLab) here. Thanks
https://youtu.be/WX_X3XlbKRA
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