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We study the mechanism of surface adsorption of organic dyes on graphene, and successive exfoliation in water of these dye-functionalized graphene sheets. A systematic, comparative study is performed on pyrenes functionalized with an increasing number of sulfonic groups. By combining experimental and modeling investigations, we find an unambiguous correlation between the graphene-dye interaction energy, the molecular structure and the amount of graphene flakes solubilized. The results obtained indicate that the molecular dipole is not important per se, but because it facilitates adsorption on graphene by a "sliding" mechanism of the molecule into the solvent layer, facilitating the lateral displacement of the water molecules collocated between the aromatic cores of the dye and graphene. While a large dipole and molecular asymmetry promote the adsorption of the molecule on graphene, the stability and pH response of the suspensions obtained depend on colloidal stabilization, with no significant influence of molecular charging and dipole.

Graphene exhibits exceptional mechanical, optical and electrical properties that are unfortunately accompanied by poor processability and tunability of its properties. The controlled interaction of graphene with tailor-made organic semiconductors (OSs) can offer a solution to solve these two problems simultaneously. The use of wellchosen organic semiconducting molecules interacting with graphene enables optimal control over the molecular self-assembly process forming low-dimensional graphene-organic architectures. Moreover, OSs allow modulation of numerous physical and chemical properties of graphene, including controlled electrical doping, ultimately making it possible to boost the performance of conventional organic electronic devices.Significantly, the interaction of organic molecules with graphene is strong not only at short distances but it is relevant also at longer distances, up to 30 nm. This feature article reviews some of the most enlightening results in the field, giving an overview of the interaction between graphene and organic molecules, starting from the simplest systems at the molecular scale, single molecules on single layer graphene in UHV, up to mesoscopic, more complex systems i.e., thick interpenetrated layers of graphene-organic composites embedded in working electronic or photovoltaic devices.