The principle of liquid-phase exfoliation can also be used to exfoliate graphite oxide. Due to several functional groups like epoxide or hyroxyl, graphene oxide is hydrophilic and
can be solved in water by sonication or stirring.Thereby the layers become negatively charged and thus a recombination is inhibited by the electrical repulsion. After centrifugation the graphene oxide has to be reduced to regular graphene by thermal or chemical methods. It is hardly possible to dispose of all the oxygen. In fact, an atomic C/O ratio of about 10 still remains [6]. The performance of this method is very similar to liquid-phase exfoliation of pristine graphene. Only the complexity is higher,since graphite oxide has to be produced
first, wich requires the use of several chemicals. Also the obtained graphene oxide
has to be reduced afterwards, using thermal treatments or chemicals again [7]. The reduced graphene oxide is of very bad quality compared to pristinegraphene, nevertheless
graphene oxide could be the desired product. Graphene oxide modified with Ca and Mg ions is capable of forming very tensile graphene oxide paper, as the ions are crosslinkers between the functional groups of the graphene flakes [8].