Novel method for graphene functionalization

In this paper we present a novel method to obtain a stable dispersion of graphene in water using carbon quantum dots as surface active agents. In this way it is possible to achieve graphene concentrations in dispersion up to 2.7 mg ml^-1. Fourier transform infrared spectroscopy and UV-Vis measurements confirmed the presence of oxygen-containing functional groups in the graphene-carbon quantum dot (gCQD) structure, responsible for its good solubility in water. The stability of the gCQD dispersion is due to π-π interactions formed between graphene and graphene-like sites of carbon quantum dots. According to Raman spectroscopy, as well as transmission electron microscopy and atomic force microscopy analysis, graphene sheets consist of several layers.