The morphology of the samples was studied using SEM and TEM.
As shown in Figure 6(a), graphite particles are in the platelet-like crystalline form of carbon.
After acid oxidation and ultrasonication, XGO sheets become smaller and transparent (Figure 6(b)).
The sheet is so thin that electron beam can be passed through sample.
Figures 6(c) and 6(d) show the SEM and TEM images of RGO.
The reduced graphene oxide exhibits typical wrinkled structure that caused sheet folding [19, 20].