Dispersion of graphene in aqueous solutions with different types of surfactants and the production of graphene films by spray or drop coating

The performances of different kinds of surfactants for dispersing hydrophobic graphene in aqueous solutions were studied. These surfactants included cationic, non-ionic, anionic, and polymer types. The results of UV-vis analysis and sedimentation test suggested that optimum dispersion was achieved with 200-300 ppm of polyoxyethylene (40) nonylphenylether (Igepal (R) CO890), a non-ionic type surfactant. The aqueous graphene suspensions were used to fabricate graphene films by two economical techniques spray and drop coating. The graphene films have a significantly lower sheet resistance than the films of commercial nanographite conductive colloid. The graphene films dispersed with CO890 showed higher electrical conductivity than those with SDS, in consistence with the analysis of dispersion performance. Our technique for preparing stable and low viscosity aqueous graphene dispersions combined with a spray coating method can produce conductive graphene films with uniform distribution, large area, and controllable thickness at low cost. (C) 2011 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.