Hello,
I electrochemically exfoliated graphene from a graphite rod in Sodium Sulfate solution. Which was later collected by vacuum filtration and dispersed in DMF by sonication (Black appearance) . I then took the glass slides and cleaned it with piranha etch. 2-3 drops of DMF dispersed graphene were dropped onto the slides followed by a drop of water. I couldnt see the graphene film form at all. Later when the slide was heated on a hot plate in air, The DMF and water evaporated. There was a small thin see through but fuzzy patch left behind it. I tried to see if it is conductive or not by an ohm meter, and it was not..
I don't know what is wrong? Any guidance?
Also how do we grow film on PET by using dispersed garphene
If it wasn't conductive there can be two problems:
1) The graphene oxide is not reduced well or not reduced at all. In this case you need to heat at higher temperatures around 300C or may be higher but in inert atmosphere. If you can also use some other reduction methods as described in detail in this publication: http://www.sciencedirect.com/science/article/pii/S0008622311008967
2) The other probable problem that I can think of is that the dispersion wasn't uniform and therefore the film is not uniform either. In this case even though the GO might have been reduced but due to non-uniformity of the film reduced graphene oxide is in discrete disconnected patches which would give limited to no conductivity.
On a different note why don't you use hummer's method since the suspension from hummer's method is more uniform and might result in a better film.
I would like keep updated with your progress.
It will be great if I can be of any help.
Thanks & regards,
Yarjan
I read about the technique while searching for the project. I avoided hummer's method since it involved highly corrosive chemicals and took a larger time. I did literature readings on using various electrolytes.
First of all The dispersion was black when concentrated but when dilute, it had a tint of pale brown. I think thats an indication of Oxidation? Right?
I will work on reducing it using any feasible method..
I am obliged for your prompt reply! :)
Regards
Hashim
I don't think your sample is oxidated as you are just exfoliating graphite... Anyway, is you have GO the best way to reduce it is in at hydrazine atmosphere at 60 degrees during a couple of hours, followed my heating at around 200 degrees for 2-3 more hours...
My guess is that maybe to sample is to thin and/or not uniform...
Why do you add the drop of water after dropcasting your samples? To get a uniform film you should try to spin-coat for example...
Best wishes,
Concha
Dear Ms. Concha
The drop of water was added as an anti solvent to reduce the solubility of graphene in DMF. Literature says that, after adding water there should be a self assembled thin film of graphene on the solution air interface but that was not observed in my case.
I tried doing spin coating, but since the suspension was dilute, a flim coudn't form on the clean glass substrate. I can try again with a concentrated solution.
Do you know how to evaporate DMF? Does simply heating the DMF graphene suspension at temperature more than 160 (> BP of DMF) on a hot plate evaporates DMF?
Dear Hashim,
Drop casting should work, so, yes, I would recommend you to use a more concentrated solution. However, to get a good conductivity with an ohm meter, you will need a reasonably thick layer...
If you spin coat you sample, the amount of DMF left after the experiment will be low, so you can try to dry it by heating in a hot plate... A vaccum oven is another possibility.
However, my experience is that graphene is not easily attached to glass slides, so depending for what are you going to use the glass slide-graphene, probably is not the best choice... For example, to perform electrochemical experiments it has not work for me. Besides, depending on your aim, you can also try to pre-treat the glass slide with PEI, as it has been demonstrated that it helps to accommodate graphene of glass slides.
Best wishes,
Concha
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