Investigation of Quenching Mechanism in Thermoreversible Fluorescent Recording Materials of Fluorescence Using Thermochromic Fluorescence Resonance Energy Transfer

Abstract

We demonstrated reversible thermosensitive recording of a fluorescent image (TRF) using a low-molecular-weight mixture consisting of a fluorescent dye, a fluoran dye, a developer, and a reversible matrix. In this material, reversible thermoresponsive disorder-crystal transition triggers a cyclical colorless-color change of a fluoran dye, which induces on–off switching of fluorescence resonance energy transfer (FRET) from a fluorescent dye to a fluoran dye. On–off switching of fluorescence is induced by heat-promoted off–on switching of FRET. Modulation of fluorescence is held at room temperature by utilizing thermal hysteresis, and nondestructive readout of the fluorescent image is accomplished in the presence of excitation light. Here, we investigate the on–off switching mechanism of fluorescence in this recording material. We analyzed the theoretical factor of emission quenching in the erasing state by comparing the theoretical overlap integral Ω between fluorescent dyes and fluoran dyes on the basis of the FRET theory with experimental emission contrast for various combinations of fluorescent dyes and fluoran dyes. It was proved that fluorescence on–off switching occurs mainly by concentration quenching due to the aggregation of fluorescent dyes and FRET from isolated fluorescent dyes to colored fluoran dyes. The key issue to obtain both high-contrast fluorescence and high fluorescence quantum yield is to control these two factors.