Production and stability of mechanochemically exfoliated graphene in water and culture media

The preparation of graphene suspensions in water, without detergents or any other additives is achieved using freeze-dried graphene powders, produced by mechanochemical exfoliation of graphite. These powders of graphene can be safely stored or shipped, and promptly dissolved in aqueous media. The suspensions are relatively stable in terms of time, with a maximum loss of ∼25% of the initial concentration at 2 h. This work provides an easy and general access to aqueous graphene suspensions of chemically nonmodified graphene samples, an otherwise (almost) impossible task to achieve by other means. A detailed study of the stability of the relative dispersions is also reported.