Like carbon nanotubes and many other nanomaterials, a key challenge in the synthesis and
processing of bulk-quantity graphene sheets is aggregation. Graphene sheets, which have a
high specific surface area, unless well separated from each other, tend to form irreversible
agglomerates or even restack to form graphite through van der Waals interactions. This
problem has been encountered in all previous efforts aimed at large-scale production of
graphene through chemical conversion or thermal expansion/reduction2–5. The prevention of
aggregation is of particular importance for graphene sheets because most of their unique
properties are only associated with individual sheets. Aggregation can be reduced by the
attachment of other molecules or polymers onto the sheets4–6. However, the presence of
foreign stabilizers is undesirable for most applications. New strategies to produce relatively
clean graphene sheets in bulk quantity while keeping them individually separated are
required.