Exfoliation and dispersion of graphene in ethanol-water mixtures

Graphene has attracted much attention as a new nano-carbon for its unique structure and properties. However, production and dispersion of unfunctionalized graphene are still big challenges. Herein, we demonstrate a simple method for preparation and dispersion of such graphene with low cost and non toxicum. This approach is achieved by exfoliating graphite in an ethanol/water mixture and forming stable dispersion of mono- and few-layer graphenes. The ratio of ethanol/water in the mixture is found to be crucial to both the exfoliation and dispersion processes. Exfoliation in pure water or pure ethanol produces no graphene. This method avoids the conventional use of harsh oxidants and surfactants; therefore, the graphitic structure is well maintained without destruction. Benefiting from the use of ethanol and water, it can be easy to prepare transparent and conductive graphene films by vacuum filtering or spray method, and does not need special post-treatment to remove the impurity, which could be beneficial for potential applications in electronic, optic and energy areas.