I want to keep my pencil graphite electrodes for a while in the aqueous graphene oxide solution that I have prepared at different concentrations such as 5 mg/mL, 1 mg/mL, 0.5 mg/mL, and then i would like to make graphene oxide adsorbed on the surface of PGEs and then i will reduce the graphene oxide electrochemically. After a while, the solution becomes heterogeneous as it begins to precipitate. Have you ever encountered such a situation before? It sounds good to dissolve it in a phosphate or acetate buffer solutions, in case this may related with pH, has anyone experienced it?
That depends upon how do you prepare graphene oxide. Do you purchase it, or prepared by modified hummer method?
Dear @Khaled Faisal Qasim, i have prepared by modified Hummer's method.
Dear Dr. Zeynep Turk,
A moderate acidic media (pH 3.2: 6) makes relative good suspension for graphene oxide (based on previous experience). You can do that by acidfication of mixture (pH 1), then followed by washing with distilled water. Buffer is also good, but it's preferable to avoid any contaminants from any ions not to affect on your experiment (buffer ions may be adsorbed on surface of graphene oxide)
Regards
Dear Dr. Khaled Faisal Qasim,
I have just dissolved graphene oxide in acidic phosphate buffer with pH 2.0, I think it looks like it will be suspended. I totally agree with you about not using buffer solutions due to the fact that aqueous acidic medium would be better to get rid of ions easily. I'm going to soak (submerged position) it in this solution overnight but let it dry and then wash with distilled water before reducing electrochemically. Do you think that the adsorbed graphene oxide on the PGEs will be dissolved with distilled water? Dear Dr. could you please explain this part? I'm grateful for your kind response.
Yours Sincerely
Dear Dr. Zeynep Turk
Both Graphite, graphene oxide doesn't dissolve in water, may PGE is corrodes in buffer if its quality isn't good. But majorly, graphite has corrosion resistance property against moderately acidic media (especially in buffer media)
Regards
- Add filesZeynep Turk , if your GO dispersion is per se stable and does not precipitate spontaneously, it most likely originates from the hydroxide ions produced on the cathode in electroreduction process. GO nanosheets tend to precipitate upon introduction of hydroxide ions as result of removal of the oxidation debris attached on their basal plane. In fact, during the synthesis procedure some highly oxidized polycyclic aromatic hydrocarbons are formed which attach to the GO and make it highly hydrophilic. However, these species are detached at high pH values and GO nanosheets precipitate immediately. So, if you are confident that your GO is highly hydrophilic and the prepaired dispersion is stable over time, I suggest you use a proper buffer solution with low ionic strength. Note, high ionic strength can precipitate GO as well, so try to use a dilute buffer with nearly acidic pH. Not to mention, if I were you, I would drop cast and dry GO disperion on the surface of the pencil graphite and then heat it for a while in an oven at 80 degrees. Afterward. I would sufficiently reduce the bonded GO using several successive cyclic voltommetry cycles. By the way, if you merely want to deposit rGO on the pencil electrode and the electroreduction does not matter to you, it is more convenient to drop cast GO and then reduce it at high tempratures. Anyway, as I stated above, it is probable the problem arises from your GO itself. So if your dispersion does not look like the attached photo, I suggest you synthesize GO again. I have optimized and reported the GO synthesis conditions by improved hummers method in the following paper. It may help you to get a high quality GO. Please note, the drying conditions reported in the article is a determinant step and should not be ignored.
Article Self-assembled graphene-based microfibers with eclectic opti...
Best,
Dear Dr. @Mahdi Ghamsari ,
I really thank you for your clear explanations, i will assess your suggestions. My solution of GO tends to blackish and results of UV and images of SEM are confirmed with the literature. Do you think black colour is a problem? Maybe as you citated that it would be important to synthesize again for using it freshly. I will read your article that you have shared with us. Due to the fact that i use pencil leads as an electrode, drop casting may be difficult for me, so i tried to dip the leads into the solution overnight. Thanks for your contribution again.
Best regards
Dear Dr. @Khaled Faisal Qasim, thanks for your contributions too. I will take into consideraton your suggestions.
Best Regards
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