Spectroscopic study of the interaction between rhodamine B and graphene

Abstract

The interaction between rhodamine B (RhB) and varying concentrations of graphene in aqueous dispersion was studied with spectroscopic techniques. Absorbance measurements indicate the formation of an RhB–graphene complex with an association constant of 21.02 ml/mg. Fluorescence quenching studies reveal that graphene is a good quencher of RhB emission and that the RhB-graphene complex is non-emissive in nature, leading to an apparent quenching efficiency of 94%. However, after correction for inner filter effects and a significant decrease in RhB absorbance due to complex formation, a more realistic quenching efficiency of 49% was obtained. Subsequent Stern–Volmer analysis revealed that the quenching mechanism is likely to be a combination of both static and dynamic quenching. Since the association constant obtained from fluorescence quenching data (22.7 ml/mg) matches well with the value from absorbance data, it is likely that static quenching due to complex formation accounts for most of the observed quenching. The possibility of photoinduced electron transfer (PET) or Förster resonance energy transfer (FRET) is discussed in terms of FRET parameters and thermodynamic consideration. Both the good fluorescence quenching and the favourable driving force for PET suggest that RhB and graphene could be a promising donor–acceptor pair for emerging photovoltaics.