Annealing a graphene oxide film to produce a free standing high conductive graphene film

A free-standing graphene oxide film (GOF) obtained by self-assembly at a liquid/air interface was annealed in a confined space between two stacked substrates to form a free-standing highly conductive graphene film. Characterization indicates that the oxygen-containing functional groups (e.g. epoxy, carboxyl, and carbonyl) were removed as small molecules (e.g. H ₂O, CO₂, and CO) during the annealing, meanwhile the size of sp² domains in the film was decreased. When annealed between two stacked wafers, random interlayer expansion and fractional movement in the GOF were suppressed by the pressure-induced friction, which helps preserve the morphology of the film. The conjugation in the basal plane of graphene and π-π interactions between well stacked graphene sheets favor the transportation of charge carriers in the film, to produce a good electrical conductivity of the resulting free-standing reduced GOF (increased from 1.26 × 10^-5 to 272.3 S/cm).