title: Unraveling Triplet Excitons Photophysics in Hyper-Cross-Linked Polymeric Nanoparticles: Toward the Next Generation of Solid-State Upconverting Materials.
abstract: The technological application of sensitized upconversion based on triplet-triplet annihilation (TTA) requires the transition from systems operating in liquid solutions to solid-state materials. Here, we demonstrate that the high upconversion efficiency reported in hyper-cross-linked nanoparticles does not originate from residual mobility of the embedded dyes as it happens in soft hosts. The hyper-reticulation from one side blocks the dyes in fixed positions, but on the other one, it suppresses the nonradiative spontaneous decay of the triplet excitons, reducing intramolecular relaxations. TTA is thus enabled by an unprecedented extension of the triplet lifetime, which grants long excitons diffusion lengths by hopping among the dye framework and gives rise to high upconversion yield without any molecular displacement. This finding paves the way for the design of a new class of upconverting materials, which in principle can operate at excitation intensities even lower than those requested in liquid or in rubber hosts.
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Monguzzi
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Mauri
authors.affiliation: Institut Lavoisier UMR-CNRS 8180, Université de Versailles Versailles-Saint Quentin en Yvelines , 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Frigoli
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Pedrini
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Simonutti
authors.affiliation: Institut Lavoisier UMR-CNRS 8180, Université de Versailles Versailles-Saint Quentin en Yvelines , 45 Avenue des Etats-Unis, 78035 Versailles Cedex, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Larpent
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Vaccaro
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Sassi
authors.affiliation: Dipartimento di Scienza dei Materiali, Università Milano Bicocca , via R. Cozzi 53, 20125 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Meinardi