Hi, you can use this reference, it is about an improved method for graphene oxide preparation using KMnO4 and 9:1 mixture of H2SO4/H3PO4. http://pubs.acs.org/doi/abs/10.1021/nn1006368?journalCode=ancac3
You may use a simple setup to ignite an arc using AC supply around 50V and some 10's of Amperes between graphite rods in deionized water. This method was suggested by Biro et al in 2003(Chem Phys Lett 2003:399–402) and subsequently modified by applying ba magnetic field to increase the quantity and improve the quality of production. This was published by us in 2007 Nano Trends: 2, 48-59.