Rhodamine 101-graphene oxide composites in aqueous solution: the fluorescence quenching process of rhodamine 101.

The interaction of rhodamine 101 (Rh101) with graphene oxide (GO) in aqueous dispersion was examined using advanced spectroscopic techniques. Rh101-GO composites in water were easily prepared by mixing an aqueous solution of both components since GO sheets interacted with the cationic dyes via π-π and electrostatic cooperative interactions. In the composites, the fluorescence of Rh101, which was a well-known laser dye with a high fluorescence quantum yield, could be efficiently quenched by GO. The quenching mechanism of Rh101 by GO sheets was evaluated by the Stern-Volmer (SV) equation and the time-resolved fluorescence studies. The results revealed that the fluorescence quenching of Rh101 by GO in the aqueous dispersion is due to the static quenching mechanism. The formation of the Rh101-GO composites at various pH values was spectroscopically monitored, and the spectroscopic results revealed that the composites were formed at the pH values studied except in the strong acidic media (pH ≈ 2). The interaction of Rh101 with GO in aqueous solution was spectroscopically followed in the presence of SDS (sodium dodecyl sulphate) at the surfactant concentrations above and below the CMC (critical micelle concentration). The fluorescence studies revealed that the fluorescence of Rh101 in the aqueous solution remarkably increased at the surfactant concentration forming the micelle of SDS.