Dry expandable graphite flakes (3772, Asbury Graphite Mills USA) were first thermally treated (at 1050 °C for 15 s) and then used as precursor for GO synthesis. Briefly, expanded graphite (5 g) and sulfuric acid (0.5 L) were mixed and stirred in a flask. Then, KMnO4 (50 g) was added to the mixture dropwise then mixed for overnight. The mixture was transferred into an ice bath, and Milli-Q (1 L) water then H2O2 (250 mL) were poured slowly into the mixture, realizing a colour change of the suspension to light brown then to yellow. Having stirred for another 30 min, the GO particles were then washed and centrifuged with a HCl solution (9:1 water/HCl by volume), then centrifuged again and washed with Milli-Q water until the pH of the solution became about 4. The resultant large GO sheets were dispersed in deionized water by gentle shaking.

Advanced Functional Materials 23 (43), 5345–5354

Thank you for answering my question

Hummers method is good I prepare and compare different method for graphene or GO

I was synthesised single go and g in larg scale and i can to send to you.

thanks dear masoud zare, but I ma not in Iran

could u tell me , which method u follow?

Synthesis of graphene oxide

Graphene oxide was synthesized from purified natural graphite by a modified Hummers method. 100 g of natural graphite was added into 5L concentrated sulfuric acid that had been cooled below of 5oC in an ice-bath. After 1 hour, 300 g potassium permanganate was slowly stirred into the mixture to prevent its temperature from exceeding 5oC. After 1 hour, the ice-bath was removed and the mixture was brought to 35-40oC, where it was maintained for another 1 hour. 5L of de-ionized water was slowly added into the mixture, the temperature was increased to about 100oC. The diluted mixture was maintained at this temperature for 1 hour. The mixture was diluted with 5L de-ionized water and then 300ml H2O2 was slowly added into the mixture and then treated with hydrochloric acid (10%, 10 L). While the mixture was still warm, it was filtered resulting in a yellow-brown filter cake. The obtained cake was washed with de-ionized water repeatedly until the filtrate became neutral to remove remaining salt impurities. The dry graphene oxide was obtained by drying the finally product at 60oC for 24 h.

Synthesis of reduced graphene oxide (RGO) or grapheme

Chemical reduction of graphene oxide to reduced graphene oxide or graphene was done according to previous reports. In a typical experiment, 5g of graphene oxide was dispersed in 5L of distilled water for 2 h using a mechanical stirring. The pH of the solution was adjusted to 10 by addition of NaOH and 20 ml of hydrazine hydrate was added to the solution and the temperature was raised to 95oC and stirred for 6h. After the reaction was completed, the graphene was collected by filtration as a black powder. The obtained powder was washed with distilled water several times to remove the excess hydrazine and the final product was dried in a vacuum oven at 100oC.

Based on the crytal size of the starting materiel graphite, the extent of oxidation Time varies. If it is in micron size givemore time, if it is nm size give less time. As per my experience give longer time for the oxidation process so that the crystal structure of the Graphite loosens , and hwn it is reduces you can see the formation of Graphene oxide very clearly. I have experienced this.

Dear gouse peera

thanks for your kindly response ....which method you used for synthesize and Base your exprience howlong is the oxcidation process enough ..do u thinck 3 days is ok?

Thank you for your prompt reply and for all your kindly assistance

If u need it in small quantities u can also buy them from suppliers like graphene supermarket. It's about $180 for few grams. But if u need a small amount it's worth doing that rather than spending a days trying to filter-resuspend etc.

Hummer's method is best to prepare the gaphene oxide now i have preppared in this method and easy to prepared in this method.

Dear Masoud Zare

Could you tell me which paper you follow for synthesis GO?

THANKS

I was synthesised single go and g in larg scale by modified Hummer's method.If you need it in larg quantities u can also buy them from suppliers like graphenexpert.com. It's about $ 50 for few grams.

I was synthesised few layer graphene that dispersed in water in larg scale by a new method.

·I am working at nanotechnology center in Research Institute of Petroleum Industry (RIPI).

email adress: [email protected] Tel: 09375069522 and 09128195368

the other adress is graphenexpert.com

I was synthesised single go and g in larg scale by modified Hummer's method in 1-2 days.

In my recent paper titled Temporospatial Control of Graphene Wettability, I have compared Raman spectra of single layer graphene and single layer graphene oxide with different oxygen content. It might help you.

http://onlinelibrary.wiley.com/doi/10.1002/adma.201503444/abstract

How to purify Graphene Oxide if don't have centrifuge?

For easy and effective synthesis of GO, you can explore this link

http://www.instanano.com/nanomaterial-synthesis/carbon-nanomaterial/synthesis-graphene-oxide-hummers-method/

Very easy way for Graphene Oxide synthesis,

http://instanano.com/nanomaterial-synthesis/carbon-nanomaterial/easy-synthesis-of-high-quality-graphene-oxide-new-method/

Hello everyone,

Can you show me how to maintain temperature at 50C or 35C. Because in my case I set up at 50C but it kept increased to 90-100C. I thought that maybe because of the oxidation reaction was continued happen? Please let me know if you know it? Thanks a lot ^^