Well, 295 eV is very high energy and should correspond to some compound with A LOT of charge transfer.

How about K2CO3, etc...???

Dear Narasimhan, did you carefully checked the calibration of your instument? Can you exclude charging effects of your sample? 295 eV is a really striking large binding energy for C1s level - typically only strongly oxidizing ligands such as fluorine may create such effects. So it could be a shake-up or another type of resonance... But again, the binding energy appears extremely large. Kind regards, Dirk

Dear Burgos, 

I dont think the other compounds may interfere. Because it is just reduced graphene oxide layers. In some papers they have mentioned that it could be CF vibrations. But still unknown.

Well, the 'just reduced' GO has something.

Can you show the spectrum?

Hi.. Please find the attached C 1s spectrum. 

The spectrum looks nice and well aligned to the C-C C1s at 285 eV, so the calibration seems to be o.k. But I think simply assuming graphene oxide is unlikely, compare e.g. to the spectra published under www.graphenea.com or see the nature paper: http://www.nature.com/ncomms/journal/v4/n2/full/ncomms2448.html

In those spectra, no indications for satellites at large binding energies are evident. So what about other elements?

Clearly you don't have graphene oxide. Your sample seem to have a lot of contamination and other elements. Especially those huge peaks at high energies. Compare to the Figure of the paper that Dirk mentioned (I attach).

I feel that Fernando is right with his first assumption of potassium (K) in your sample: The doublett at 293 and 295.5. eV pretty much resembles the K 2p3/2 and 2p1/2 doublett in terms of energy separation and intensities of the two peaks. Although the binding energies are a bit too small ...

by taking a look to the spectrum you shared, I'm afraid your sample contains much much much fluorine. Check these data:

Article Synthesis of a Fluorinated Graphene Oxide-Silica Nanohybrid:...

Thanks Dirk and Burgos. Yes, I agree with the nature paper. So Do you all mean to say that the peak centered at 295eV peak is not from rGO and it could be some high contamination present in the compound. I thiink I should redo the XPS analysis. 

Does the pegylation of these rGO can cause some kind of peak to the spectrum.? 

Check in any case the F1s spectrum at about 697 eV binding energy!

Dear Dirk,

I could not find any peak between 600 eV to 900 eV. Not even a small peak that I could find in the wide spectrum. I could not find any F 1s spectrum. But as you all said there are some K 2p peak in that range. This could be due to contamination.?

Yes, potassium (K) can be a contaminant. I however do not which source can be likely in your case, sorry ...

I agree, potassium is the likely contaminant giving rise to K2p 3/2 at ~293 eV and K2p 1/2 at ~295 eV respectively. Graphene oxide is usually synthesized using potassium permanganate (and also potassium nitrate) so could this be the source of your potassium contamination? 

Thanks Martin, Yes this could also be a reason. But the source i used to produce graphene oxide is from HOPG.

I produced rGO from HOPG. Do you think HOPG will also contain some potassium content between graphene layers.?

Dear Narasimhan, I think it's quite unlikely there would be any intercalated potassium between the HOPG layers. How did you synthesize the graphene oxide? 

Dear Narasimhan, PEGylation could cause the insurgence  of C-C and C-O peaks. The trace you provided, instead, might be either contaminated by fluorine or in its Salt form (potassium Salt of graphene oxide). 1) Wash it with acidic water (just 2-5% HCl) and repeat the analysis; 2) try to perform EDX mapping

Dear Andrea, I think it is likely due to the presence of potassium salt from graphene oxide. Whether the acid water treatment would cause removal of PEG from the Graphene.? Do you think that the peak shift as I showed in the graph could be due to addition of PEG? 

Dear Martin, I synthesize these GO using with nanosecond laser ablation and I think this could produce some multi layered GO which can have some potassium as inter chelating agent in between the layers.