Chemically modified graphene sheets by functionalization of highly exfoliated graphite

Abstract

Highly exfoliated graphite (HEG) containing multi-, bi- and monolayer graphenes has been prepared from an alternative class of precursors – fluorinated graphite intercalation compounds, namely, poly(dicarbon fluoride) intercalation compounds C₂F·xR. Treatment of HEG by mixture of concentrated nitric and sulfuric acids results in chemically modified graphenes (CMG) dispersible in water or alcohol medium without any surfactants or stabilizers. The samples were examined by elemental analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM), IR, Raman and UV-vis spectroscopies. Elemental analysis and IR data indicate that covalent functionalization with oxygen-containing groups, such as carboxyl group, occurs upon acid treatment. AFM images show thin sheets of about 1 nm, confirming the well-dispersed state of the material. Dispersions of CMG sheets from highly exfoliated graphite are very stable colloids (over a year) and can serve for further functionalization.