Hybrid Systems Based on Layered Silicate and Organic Dyes for Cascade Energy Transfer

This work describes the multistep Förster resonance energy transfer (FRET) among laser dyes adsorbed onto the nanoparticles of a layered silicate, saponite (Sap). Six cationic laser dyes with appropriate spectral properties to fit the resonance conditions were selected. Fluorescence spectroscopy proved cascade FRET in the experiments based on hybrid colloidal systems. The emission from preferentially excited energy donor molecules was reduced in favor of the emission from energy acceptors. The colloidal systems were used for the preparation of thin solid films with embedded dye cations. The films were characterized by X-ray diffraction, absorption spectroscopy, and linearly polarized absorption spectroscopy. Results from steady-state fluorescence, fluorescence anisotropy measurements, and time-resolved fluorescence spectroscopy confirmed the occurrence of a cascade FRET in the films. The effect of the concentration of embedded dye molecules on FRET efficiency was proved. The multicomponent films based on Sap and laser dyes are affordable materials useful for the manipulation of light energy at a molecular level, thus mimicking a cascade process occurring in photosynthesis systems in green plants.