Fluorescence quenching of cationic organic dye by graphene: interaction and its mechanism

Graphene, an extended conjugated system, is an efficient fluorescence quencher for various organic dyes and quantum dots. In this Letter, rhodamine 6G (R6G) was used as a typical representative probe molecule to investigate the interaction between graphene and cationic organic dye. The as-prepared graphene oxide and graphene were characterised by UV-vis spectroscopy, infrared spectroscopy and atomic force microscope, respectively. The interaction between graphene and R6G was studied by various spectroscopic techniques. The results revealed that no ground state complex was formed in the presence of graphene. The observed fluorescence quenching of R6G by graphene went through an electron transfer process. The Stern-Volmer analysis indicated that the strong ability of graphene to quench the intrinsic fluorescence of R6G was based on a dynamic quenching mechanism. The fluorescence decay analysis of R6G in the presence of graphene showed a remarkable decrease in lifetime from 4.42 to 3.94-ns, which further confirmed that photoinduced electron transfer occurred between them, and the quenching of R6G by graphene was dynamic in nature.