On the role of applied potential in adsorption of dibenzyl viologen molecules on HOPG surface

Tuning the charge carier concentration of graphene is one of the key challenges in the field of graphene research. An effective solution for this is to dope graphene by organic molecules that physisorb or self-assemble on the graphene surface. Therefore, a comprehensive understanding of their surface structures at the molecular level is realy nessesary. In this contribution, we report on the role of the applied electrode potential in the adsorption/self-assembly of such n-dope molecule, dibenzyl viologen (DBV), on a highly oriented pyrolytic graphte (HOPG) surface (a multi-layer graphene material) determined by using a combination of cyclic voltametry (CV) and electrochemical scanning tunneling microscopy (ECSTM) methods. The obtained results reveal that dibenzyl viologen molecules can exist at three redox states corresponding to three respective adsorbate phases depending on the applied electrode potential. The DBV2+ molecucles physisorb and form disordered phase, whereas DBV·+ and DBV0 moleucles self-assemble forming dimer and stacking phases, respectively, on HOPG surface.