Figure 1 shows the obtained graphite oxide, graphene oxide,
and reduced graphene oxide suspension in water. Graphite
oxide prepared by a modified Hummer’s method creates a
brown aqueous suspensionwhen dispersed inwater as shown
in Figure 1(a). The exfoliation of bulk graphite oxide in an
ultrasonicbathresults inabrowncolor and semitransparency
of graphene oxide (Figure 1(b)). The negative surface charge
of graphene oxide induces electrostatic repulsion among
them and making it strongly hydrophilic [7]. However, when
the graphene oxide was reduced in hot water, black precipitates
are formed (Figure 1(c)). This is a typical hydrophobic
characteristic of RGO or graphene sheets with less polar
functionality on the surface of the sheets, compared to that
of XGO [8].