Reduction of Suspended Graphene Oxide Single Sheet Nanopaper: The Effect of Crumpling

The recent development of aerosol generated crumpled graphene oxide nanopaper provides a test bed for studying the reactivity of physically deformed graphene-based materials. In this work, we measured the thermal reduction of aerosolized single sheet, crumpled graphene oxide (GO) nanopaper. Online aerosol mass analysis was used to monitor the mass evolution of individual crumpled GO nanopaper during reduction. For the first time, the extent of sp(2) bonding within the material was characterized using photoacoustic spectroscopy. The chemical composition of reduced GO nanopaper was evaluated using X-ray photoemission spectroscopy (XPS). Thermal reduction kinetics was determined using both the loss of mass and the change in optical absorption, each measured as a function of temperature. The activation energies were different for the two techniques, suggesting mass loss and light absorption probe different processes of GO reduction. We measured a constant effective density at high reduction temperatures suggesting that portions of reduced GO unzip from the sheet similar to what has been observed in oxidized graphene.