Interaction of Rhodamine 6G molecules with graphene: a combined computational–experimental study

In this work, the adsorption of Rhodamine 6G molecules on some graphene substrates is investigated using density functional theory. Some simple models, such as those of perfect graphene, defective graphene, *O/*OH modified graphene and B/N doping graphene, are constructed as substrates to simulate graphene oxide and B/N doping graphene sheets. It is demonstrated that the interactions of Rhodamine 6G molecules with graphene materials are strong. In particular, the amine group of Rhodamine 6G molecules can favor the formation of a chemical bond with some graphene substrates characterized by under-coordinated atoms. The chemical interactions would lead to significant changes in the electronic structures of graphene substrates, which have the potential to tune the electronic properties of graphene. In addition, our calculations predict that the epoxy/hydroxyl group attached to the surface of graphene could be removed by Rhodamine 6G molecules, which suggests that the reduction reaction may occur in graphene oxide upon Rhodamine 6G doping. The surface plasmon resonance spectra of R6G adsorbed on some graphene substrates are also characterized, which are well in agreement with some computational results. Therefore, combined with experimental observations, our results provide an insight into the interaction of Rhodamine 6G molecules with graphene materials.