Abstract
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Research on graphene was originally motivated by its
peculiar electrical transport properties and the promise of
future applications in nanoelectronics.[1,2] Graphene sheets,
owing to their exceptional thermal and mechanical properties
and high electrical conductivity, are also of great interest to
serve as new nanoscale building blocks to create unique
macroscopic materials.[3–5] Recent studies have shown that
graphene sheets can be prepared in large quantity through
chemical conversion from graphite,[6–12] which has facilitated
the fabrication of graphene-based electronic devices[13,14] and
has also made it possible to create new bulk materials
comprising graphene sheets for a broader range of applications.[
3–5,15,16] For example, it has been recently demonstrated
that chemically modified graphene sheets can be dispersed
throughout a polymeric[3] or inorganic matrix[15] to make
electrically conducting composites with a percolation threshold
as low as 0.1 vol %. Thin graphene films have also been used as
potential transparent electrodes for solar cells.[16] More
recently, Ruoff and co-workers have demonstrated that graphene
oxide (GO) sheets dispersed in water can be assembled into
a well-ordered structure under a directional flow, yielding
ultrastrong GO paper.[4] GO paper is superior to many other
paperlike materials in stiffness and strength, however, a lack of
electrical conductivity limits its use. Although GO paper can
be rendered conductive by thermal annealing, the structure
and mechanical properties seriously deteriorate after this
treatment (see below for further discussion).