Benitez-Martin, CarlosLi, ShimingDominguez-Alfaro, AntonioNajera, FranciscoPérez-Inestrosa, EzequielPischel, UweAndréasson, Joakim2023-02-092023-02-092020-08-21http://hdl.handle.net/10668/16107The combination of two two-photon-induced processes in a Förster resonance energy transfer (FRET)-operated photochromic fluorene-dithienylethene dyad lays the foundation for the observation of a quartic dependence of the fluorescence signal on the excitation light intensity. While this photophysical behavior is predicted for a four-photon absorbing dye, the herein proposed approach opens the way to use two-photon absorbing dyes, reaching the same performance. Hence, the spatial resolution limit, being a critical parameter for applications in fluorescence imaging or data storage with common two-photon absorbing dyes, is dramatically improved.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/research article32799520open access10.1021/jacs.0c073771520-5126PMC7498150https://pubs.acs.org/doi/pdf/10.1021/jacs.0c07377https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498150/pdf