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