I have synthesized GO by following Hummers methods. After completing the synthesis, I washed it with 10 % HCl several times and then started washing with DI water. However, the pH of GO is not increasing that much. It seems that pH is sticks to around 4. what could be the reason behind that? How can I get rid of this problem?
Hello Tanvir, there are several reasons that may contribute to it:
1) there are many oxygen enriched functional groups -OH, -COOH, the pKa may be around 4.
2) the hydroxylation effect among oxides. It is common in metal oxides but not sure if it can work for GO.
3) washing is not enough. Sometimes it takes me 5-8 hours to wash the nanoparticles I synthesize before it can approach neutral.
Possible solution:
You can try to adjust the pH to 7 by NaOH solution with proper concentration. Then wash it with DI, test the pH. Normally this will save time and will work. If not, accept it and may be that's one of the properties of GO as the oxygen enriched groups make the GO like a weak acid. If you want to study the property of GO under pH 7, just use buffer solution to do it. Hope it is helpful.
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