Dear Ashwin,

I agree with the suggestion made by Feliu. You must check the variation of nitrogen content with sputter etching time.

I don't know whether you have deposited this Graphene oxide on any substrate??

Please make more clear.....

Literature says some times the nitrogen in the atmosphere gets adsorb on the GO which may give the Nitrogen peak when the sample tube is not tight properly. But try to analyse the % of N as suggested by the Professor Feliu and Srivastava. If the Atomic % is very less need not to worry. Make sure that no Nitrogen precursors were taken in the synthesis process. For a blank experiment take the XPS of the starting material also for the conformation.

Please specify more details - how thick is your GO film and on what substrate is it supported for XPS?

i also want to know how to perform a XPS analysis of antibody-nanoparticle conjugate. It's difficult to obtain a film or powder shape samples of antibody-nanopartice conjugate. We generally use it in liquite form. i d pleased if u can offer a method.

You might also try angle-resolved XPS to see whether your N1s / C1s ratio indicates a surface film or not.

If the GO is in the form of a film then ARXPS should help determine if surface related as already mentioned. If powder, or 'platelets' then the different scattering angles may cause complications with the ARXPS - but doesn't hurt to try anyway.

I have studied a large number of GO samples and there is often N present, typically as NHx (BE ~399.5-400 eV) and attributed to atmospheric pick up or from ammonium ions in solution - preparation dependent of course. As you are getting a value around 398 eV, this could be perhaps be pyridinic, nitrogen or alkyl nitriles? (See for example R. J. Jansen, H. Bekkum, Carbon, 1995, 33, 1021-1027).

Another thought is depending on the source of carbon for your GO preparation, any Si present (typical contaminant in carbons) could potentially form Si-N bonds so could be an explanation too?

Usually there is not nitrogen on the good quality graphene. If you wan t to identify the graphene by using XPS technique, it is necessary to acquire C KVV Auger peak. It is diamond-like In the case of graphene. You can read about this effect in: S. Kaciulis et al., Surface and Interface Analysis, 2014, published on-line, DOI 10.1002/sia.5382

Well, depending on how thick is your film, you might want to cleave it with a scotch tape before performing XPS. This is what we did and the cleaved samples didn't exhibit any nitrogen spectral feature. Moreover, I think the ability for nitrogen adsorption onto the films depends upon the source material because we did not observed any nitrogen signal when we were testing the influence of sulfur containing moieties on the film growth.

Every reagents in a synthesis process include nitrogen in its chemical composition (Hammers or Brodie methods). Therefore the presence of N in a spectrum could be very natural. The formation of the nitrogen containing groups in GO is very probably.