Toward Two-Photon Absorbing Dyes with Unusually Potentiated Nonlinear Fluorescence Response

Abstract

The combination of two two-photon-induced processes in a Förster resonance energy transfer (FRET)-operatedphotochromic fluorene-dithienylethene dyad lays the foundation for the observation of a quartic dependence of the fluorescencesignal on the excitation light intensity. While this photophysical behavior is predicted for a four-photon absorbing dye, the hereinproposed approach opens the way to use two-photon absorbing dyes, reaching the same performance. Hence, the spatial resolutionlimit, being a critical parameter for applications in fluorescence imaging or data storage with common two-photon absorbing dyes, isdramatically improved