Enhanced Fluorescence behavior of Safranine-O by complexing with inorganic clay nanosheets

Our laboratory has been studying the strong enhancement in the fluorescence quantum yield and an excited lifetime of the organic dye molecules on the clay nanosheets and refer to as “Surface-Fixation Induced Emission”. In this study, Safranine-O which is a mono-cationic phenazine-based dye molecule, was used as the organic dye. It has fluorescence enhancement properties on the clay surface due to the suppression of the non-radiative deactivation rate constant (k_nr) on the clay nanosheets. While Safranine-O in water in the absence of clay nanosheets exhibited the values as 0.068 and 1.09 × 10⁻⁹ s for ϕ_f and τ, those on the clay surface are 0.121 and 1.96 × 10⁻⁹ s. k_nr values in water and on the clay were calculated to be 8.6 × 10⁸ s ^− 1 and 4.5 × 10⁸ s ^− 1, respectively. These results can be explained well by the structure fixing and structure resembling effect. This study helps to explore the possibility of utilizing mono-cationic dye molecules for the realization of desired photo-functional materials and photochemical reactions.