Fig. 1
1 Oxidation procedures of graphite flakes (GF) by Hummers method, improved Hummers method, and modified Hummers method. The arrow and nearby NOx is gaseous nitric oxide. The right side shows generated graphite oxides as well as unoxidized or under oxidized graphite flakes that still exhibit hydrophobic property. Least amount of hydrophobic in the “improved” bottle indicates its highest oxidation efficiency [24]. 2 Synthesis of single layer graphene oxide (slGO) by K2FeO4. In intercalation oxidation (IO) stage, the in situ formed oxidants (FeO4 2− and atomic oxygen [O]) and O2 intercalate into graphite layers and form intercalated graphite oxide (GIO). Then, it is further oxidized and exfoliated by O2 in oxidation-exfoliation (OE) stage. With recycling of H2SO4 and water washing, slGO is obtained [25]