  In a deviation from the conventional Hummers method, a spontaneous expansion
approach was introduced with expanded graphite as the precursors. The
intercalating agent (H2SO4) was able to penetrate into the expanded graphite;
this had further expanded the graphite and as a result, a foam-like
intermediate was produced. The foam-like graphite was more easily oxidized in
reaction with the oxidant (KMnO4) to form graphene oxide (GO). Fully exfoliated
GO was obtained with expanded graphite having the median diameter ~ 15 {\mu}m
as the precursors. This procedure was much safer and productive in scalable
applications than the conventional Hummers methods.
