Hello.
I used Tour method and after adding H2O2, solution turn to yellow from dark brown. From the paper, it showed that oxidation of graphite flakes occur which mean Graphite Oxide form. Washing with 5% HCl and water then dilute with 400mL DI, stir and sonicate. The result characterized using FTIR and no C-OH, C-O-C, C-OH observed. Just one obvious peak (1635cm-1 attributes C=O) (most paper mentioned around 17++) was observed. Why it happened?
you should look at other methods for synthesis GO . in the literature there is an improved method for the preparation of graphene oxide (GO) is described. Currently,
Hummers' method (KMnO4, NaNO3, H2SO4) is the most common method used for
preparing graphene oxide. We have found that excluding the NaNO. This method published by
DC Marcano, DV Kosynkin, JM Berlin, A Sinitskii… - ACS …, 2010 - ACS Publications
If you are only seeing one peak at 1635 cm-1 in FTIR , then most likely your graphite hasn't oxidised. Compare the FTIR of your graphite starting material with the GO obtained. The peak at 1635 cm-1 is most likely due to O-H bending from water as well as some C=C stretching contribution.
Most probably you are doing something wrong during your oxidation steps in the very beginning - the washing step, if done incorrectly, should just leave your samples with a high degree of contaminant residues. The Marcano-Tour method works just fine, and it has even higher yields than the improved Hummers; it has gradually become the preferred standard for GO preparation, and I wouldn't advise you to switch back to the Hummers - just try to perfect your Marcano-Tour.
My guess is that most probably you did not control the temperature properly during the oxidation step: if it raises too much during your exothermal reactions, any produced GO gets reduced back to graphite. This might explain your partial oxidation.
FTIR can only give you part of the answer. I would advise you looking at the Raman spectra as well.
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