  Graphene flakes were produced by nanosecond plasma discharge at atmospheric
pressure between an electrode and the surface of distilled water, in which were
placed graphite flakes. The discharge ionizes the gas and forms free radicals
on the surface of the water, functionalizing the graphite flakes in solution.
The plasma also gives enough energy to break the Van der Waals bonds between
the graphene layers but not enough to break the covalent C-C bonds within the
layers. Transmission electron microscopy confirmed the hexagonal structure of
graphene sheets, and showed that they were monocrystalline. No contamination
was found in the obtained nanomaterial. An unknown phenomenon has been found in
the activated distilled water, making its electrical conductivity decrease with
an increasing temperature. An acidification of the water is observed. The gas
in which the discharge takes place plays a major role on the process, no
exfoliation is observed if plasmogen argon gas is used.
