Use a modified Hummers method ! Our Lab gets 20-100 nm graphene oxide nanoplatelets consistently ! See this publication: Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons -

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0038185

if you are using Hummer's method it depends on the size of starting graphite.. smaller the size of graphite, smaller will be the final graphene sheets

Thanks a lot!

Use bottom-up methods.

The preparation of graphite oxide (GO) was carried out by a modified Hummers method: In detail, a mixture of concentrated H2SO4 and H3PO4 (108:12 mL) was cooled in an ice bath and then 2.5 g of graphite and 2.5 g of NaNO3 were successively dispersed in the mixture by stirring for 10 min. Next, 15 g of KMnO4 were slowly added with continuous vigorous stirring and cooling so that the temperature of the mixture remained below 10 ∘C. The suspension was kept to react for 2 h in the ice bath. The dry ice bath was then substituted by a (35-40 C) preheated water bath and the mixture was stirred for 60 min.

Afterwards, deionized (DI) water was added slowly to reach the volume 400 mL in 60 min. Because the addition of water in concentrated sulfuric acid medium released a large amount of heat, the addition of water was performed in an ice bath to keep the temperature below 98 ◦C.

The suspension was ultrasonicated for 2 h at 30 C. the reaction was terminated by addition of 20 mL H2O2 (30 %) in 5 min. The reaction product was washed with 1L of 5% HCl solution and next with 1L deionized water. Finally, the product was dried at 70∘C for 24 h.

I used this method and got perfect result. I added the ultrsonication to get smaller sheets in area not width so I can get a more functional groups on the edge.

Regards

thank you maher

Actually, the best way to reduce the width is sonicating GO suspension for more than 4 hours. The choice of pristine graphite has a great influence on GO width but you have to take in account that the high viscosity of the slurry (during the Humemrs oxidation) breaks the lamellae into smaller ones under shear stresses, thus you will achieve a lateral size distribution from few nanometers to tens of micron. If you perform ultrasonic tearment followed by centrifugation at low speed and recover the surnatant you will be sure that GO is nanosized.

You can use ultrasonication along with its synthesize in order to reduce the final size of developed graphene oxide. Moreover, by selecting graphite sheets with low dimensions, you can also fulfill this goal.