During the synthesis of graphene oxide by modified hummer's method , the solution turns green instead of yellow by the addition of H2O2 inspite of accurate following of the procedure graphene oxide doesnot show the desired color.
Which means you the pre oxidation step wasn't successfully done. In which case you need to prolong each step little longer than usual timings and the addition of h2o2 needs to be continued until you see slight yellowish. Cheers.
From my point of view, you are adding the permanganate too quickly, do it slowlier . Once your solution has on the top of the surface a greenish colour, probably your graphite is fully oxidized, if you want to keep adding it is Ok,, but if you do some EPR measurements, you will find traces of Mn that did not react. Then, is time to let it stirred for some time and then, controlling the temperature under a water bath, adding the water drop by drop and ALWAYS being sure your temperature does not increase drastically, because this reaction is quite exothermic. Good Luck.
Hello Gul,
Do not judge the oxidation state of your GO just by the colour: this might be strongly affected by the used precursors and/or the environment conditions during the synthesis.
You should characterize your GO (and compare it with the precursor graphite) by means of other methods, such as: TGA, Raman, XPS, FTIR, etc. to claim whether the oxidation was successful or not.
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