Influence of Graphene Oxide Concentration and Fluorophore Charge on the Formation of Non-Fluorescent GO-Fluorophore Complexes

The Stern-Volmer equation is commonly used to describe the fluorescence quenching process, but its application faces challenges for quenchers with heterogeneous physicochemical characteristics (size and surface composition), such as graphene oxide. This study proposes a mathematical approach to calculate the association constant and the change in the Gibbs free energy in graphene oxide-fluorophore systems, considering the influence of quencher concentration (0.12 to 250 mu g mL-1)-1 ) and the net charge of the fluorophore on the formation of the non-fluorescent complex. It was identified that increasing the concentration of graphene oxide favors the formation of the non-fluorescent complex in the interaction with charged fluorophores, starting from 0.48 mu g mL-1-1 for methylene blue and from 31.25 mu g mL-1-1 for fluorescein sodium, predominantly leading to static fluorescence quenching. The interaction between graphene oxide and naphthalene lead to dynamic fluorescence quenching. This evaluation could be explored, for example, in nanotechnologies for environmental and biomedical applications.