Surfactant-Free Single Layer Graphene in Water

Abstract: Dispersing graphite in water to obtain true (single layer) graphene (SLG) in bulk quantity in a liquid has been an unreachable goal for materials scientists in the last decade. Likewise, a diagnostic tool for identifying solubilized SLG in situ has been long awaited. Homogeneous stable dispersions of SLG in water are obtained by mixing graphenide (negatively charged graphene) solutions in tetrahydrofuran (THF) with degassed water and evaporating the organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics of single layer graphene, including an intense 2D band of Lorentzian shape and linewidth of 28 cm-1. Transmission electron and atomic force microscopies on deposits confirm SLG character. The resulting additive-free stable water dispersions contain 0.16 mg/mL of SLG.