title: Dual fluorescence through Kasha's rule breaking: an unconventional photomechanism for intracellular probe design.
abstract: Dual fluorescence is an anomalous photophysical phenomenon observed in very few chromophores in which a two-color radiative process occurs that involves two distinct excited electronic states. To date its observation was linked either to electronic rearrangement of an excited fluorophore leading to two conformers with distinct emissive properties, or to a photochemical modification leading to different fluorescent species. In both cases, emission originates from the lowest excited state of the resulting molecular configurations, in line with the so-called Kasha's rule. We report here a combined theoretical and spectroscopic study showing, for the first time, an anti-Kasha dual-emission mechanism, in which simultaneous two-color emission takes place from the first and second excited state of a coumarin derivative. We argue that the observed environmental sensitivity of this peculiar optical response makes the present compound ideally suited for biosensing applications in living cells.
authors.affiliation: †Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Brancato
authors.affiliation: ‡Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Signore
authors.affiliation: §Dipartimento di Farmacia e Biotecnologie (FaBit), Università di Bologna, Via San Donato 19/2, 40127 Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Neyroz
authors.affiliation: ∥IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, P. za L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Polli
authors.affiliation: ∥IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, P. za L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: †Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Abbandonato
authors.affiliation: ‡Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Pisa, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Nucara
authors.affiliation: †Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Barone
authors.affiliation: ‡Center for Nanotechnology Innovation @ NEST, Istituto Italiano di Tecnologia, Pisa, Italy.|⊥NEST, Scuola Normale Superiore and NANO-CNR, Pisa, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Beltram
authors.affiliation: ⊥NEST, Scuola Normale Superiore and NANO-CNR, Pisa, Italy.|#Istituto di Biofisica-CNR, via Moruzzi 1, 56124, Pisa, Italy.
authors.forename: Ranieri
authors.initials: R
authors.lastname: Bizzarri
mesh_terms: D015374:Biosensing Techniques; D002460:Cell Line; D003374:Coumarins / Q000032:analysis*; D004583:Electrons; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes / Q000032:analysis*; D006801:Humans; D018613:Microscopy, Confocal; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D003374:Coumarins; D005456:Fluorescent Dyes