Direct chemical conversion of continuous CVD graphene/graphite films to graphene oxide without exfoliation

Graphene oxide (GO) is promising nanomaterial due to its surface versatility by substitution of functional groups and controllable d-spacing. However, most common methods to prepare GO are based on chemical exfoliation by strong oxidation agents forming flake dispersions that are used to form thin films of aggregated flakes. However, because of their discontinuous and amorphous morphology, such GO films have poor thermal, electronic and mechanical properties. Herein, we report a novel and quick method to obtain large and continuous GO multilayers by directly converting a chemical vapor deposited multilayer graphene (CVD-MG) into graphene oxide (CVD-MGO). Our oxidation procedure uses a CVD-MG grown on Nickel (CVD-MG/Ni), combining a gentle acid mixture with the mechanical support of the nickel foil to oxidize the CVD-MG without ripping the basal planes. XPS, EDX, and Raman spectra prove the complete conversion of MG to CVD-MGO. XRD also shows higher crystallinity for CVD-MGO than for Flake-GO film. By reducing the continuous CVD-MGO, we obtain conductive reduced-GO (CVD-rGO), which reaches 80% of the original CVD-MG conductance. Our directly conversion of CVD-MG to CVD-MGO shows great promise for improved transport properties of GO and enhanced performance for filtering and molecule separation.