I use graphene oxide (GO) in a variety of experiments, first of all I want to functionalize its carboxyl and hydroxyl groups. But, after the use of some base, salts and ion's solutions, I can see a significant lost of water solubility. The situation remains negative after centrifugation and after washing it with double distilled water. Never the less, in these conditions, I'm not able to functionalize the GO. In my opinion GO loses the most of its carboxyl and hydroxyl groups during the experiments, can this explain the lost of solubility and the failure functionalization? Thank you.
GO has a higher water dispensability compared to pristine graphene due to the presence of oxidative functional groups. I don't really understand why your GO is less water soluble. It depends of the oxidative method that you use to synthesize GO, maybe graphene is not completely oxidized? Also, the concentrations of GO dispersions that you are trying to prepare..
Once you start adding base, you are partially reducing the GO. You may notice a color change when adding base. Or, you can dry the material and run TGA to determine if it is partially reduced. rGO (graphene) is much harder to disperse in water, even if you have some functional groups remaining.
I am agree with Claire. adding base to GO can cause partially reduction of it.
Ok! thank you guys. Now, how can i make the situation better? How can i use GO without losing its water solubility?
If adding base & salts is absolute necessary for functionalization.... then try changing solvent or use water/organic solvent mixtures
You should analyse your "graphene oxide" before and after processing by XPS, Auger or other surface sensitive technique to confirm (or not...) your gess.
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