Scientific Results

Photochemical Control of Exciton Superradiance in Light-Harvesting Nanotubes

Year: 2018

Authors: Doria S., Sinclair TS., Klein ND., Bennett DIG., Chuang C., Freyria FS., Steiner CP., Foggi P., Nelson KA., Cao JS., Aspuru-Guzik A., Lloyd S., Caram JR., Bawendi MG.

Autors Affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, United States; European Laboratory for Non Linear Spectroscopy (LENS), Università Degli Studi di Firenze, Via Nello Carrara 1, Sesto Fiorentino, Florence, 50019, Italy; Dipartimento di Chimica Ugo Schiff, Universitàdegli Studi di Firenze, Via della Lastruccia, 3-13, Sesto Fiorentino, Florence, 50019, Italy; Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138, United States; INO-CNR, Istituto Nazionale di Ottica-Consiglio Nazionale Delle Ricerche, Largo Fermi 6, Florence, 50125, Italy; Dipartimento di Chimica, Biologia e Biotecnologie, Università di Perugia, Via Elce di Sotto 8, Perugia, 06123, Italy; Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095, United States

Abstract: Photosynthetic antennae and organic electronic materials use topological, structural, and molecular control of delocalized excitons to enhance and direct energy transfer. Interactions between the transition dipoles of individual chromophore units allow for coherent delocalization across multiple molecular sites. This delocalization, for specific geometries, greatly enhances the transition dipole moment of the lowest energy excitonic state relative to the chromophore and increases its radiative rate, a phenomenon known as superradiance. In this study, we show that ordered, self-assembled light-harvesting nanotubes (LHNs) display excitation-induced photobrightening and photo-darkening. These changes in quantum yield arise due to changes in energetic disorder, which in turn increases/decreases excitonic superradiance. Through a combination of experiment and modeling, we show that intense illumination induces different types of chemical change in LHNs that reproducibly alter absorption and fluorescence properties, indicating control over excitonic delocalization. We also show that changes in spectral width and shift can be sensitive measures of system dimensionality, illustrating the mixed 1-2D nature of LHN excitons. Our results demonstrate a path forward for mastery of energetic disorder in an excitonic antenna, with implications for fundamental studies of coherent energy transport.

Journal/Review: ACS NANO

Volume: 12 (5)      Pages from: 4556  to: 4564

More Information: J.R.C. and T.S. were funded by the Department of Energy (DOE) through the DOE Center for Excitonics (an Energy Frontiers Research Center funded by the U.S. DOE, Office of Science, Office of Basic Energy Sciences, through grant no. DE-527 SC0001088). F.S.F. was supported by Eni SpA under the Eni-MIT Alliance Solar Frontiers Center. N.D.K. was funded by the DOE Office of Science, Basic Energy Sciences through grant no. DE-FG02-07ER46454. S.D., T.S.S., N.D.K., F.S.F, C.P.S., and J.R.C. performed the experiments. T.S.S., D.I.G.B., C.C., performed simulations. All authors contributed to data interpretation and writing the manuscript. We would also like to acknowledge the reviewers for helpful feedback and ideas for additional experiments.
KeyWords: Antennas; Chromophores; Energy transfer; Nanotubes; Radiation; Superradiance; Yarn, Direct energy transfers; Excitonic delocalization; Fluorescence properties; Fundamental studies; Molecular controls; Organic electronic materials; Photochemical control; Transition dipole moments, Excitons
DOI: 10.1021/acsnano.8b00911

Citations: 8
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