1
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Gharbi AM, Biswas DS, Crégut O, Malý P, Didier P, Klymchenko A, Léonard J. Exciton annihilation and diffusion length in disordered multichromophoric nanoparticles. NANOSCALE 2024; 16:11550-11563. [PMID: 38868990 DOI: 10.1039/d4nr00325j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2024]
Abstract
Efficient exciton transport is the essential property of natural and synthetic light-harvesting (LH) devices. Here we investigate exciton transport properties in LH organic polymer nanoparticles (ONPs) of 40 nm diameter. The ONPs are loaded with a rhodamine B dye derivative and bulky counterion, enabling dye loadings as high as 0.3 M, while preserving fluorescence quantum yields larger than 30%. We use time-resolved fluorescence spectroscopy to monitor exciton-exciton annihilation (EEA) kinetics within the ONPs dispersed in water. We demonstrate that unlike the common practice for photoluminescence investigations of EEA, the non-uniform intensity profile of the excitation light pulse must be taken into account to analyse reliably intensity-dependent population dynamics. Alternatively, a simple confocal detection scheme is demonstrated, which enables (i) retrieving the correct value for the bimolecular EEA rate which would otherwise be underestimated by a typical factor of three, and (ii) revealing minor EEA by-products otherwise unnoticed. Considering the ONPs as homogeneous rigid solutions of weakly interacting dyes, we postulate an incoherent exciton hoping mechanism to infer a diffusion constant exceeding 0.003 cm2 s-1 and a diffusion length as large as 70 nm. This work demonstrates the success of the present ONP design strategy at engineering efficient exciton transport in disordered multichromophoric systems.
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Affiliation(s)
| | | | - Olivier Crégut
- IPCMS, Université de Strasbourg - CNRS, Strasbourg, France.
| | - Pavel Malý
- Charles University, Prague, Czech Republic
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2
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Zheng Y, Rojas-Gatjens E, Lee M, Reichmanis E, Silva-Acuña C. Unveiling Multiquantum Excitonic Correlations in Push-Pull Polymer Semiconductors. J Phys Chem Lett 2024; 15:3705-3712. [PMID: 38546242 PMCID: PMC11017317 DOI: 10.1021/acs.jpclett.4c00065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 03/19/2024] [Accepted: 03/21/2024] [Indexed: 04/12/2024]
Abstract
Bound and unbound Frenkel-exciton pairs are essential transient precursors for a variety of photophysical and biochemical processes. In this work, we identify bound and unbound Frenkel-exciton complexes in an electron push-pull polymer semiconductor using coherent two-dimensional spectroscopy. We find that the dominant A0-1 peak of the absorption vibronic progression is accompanied by a subpeak, each dressed by distinct vibrational modes. By considering the Liouville pathways within a two-exciton model, the imbalanced cross-peaks in one-quantum rephasing and nonrephasing spectra can be accounted for by the presence of pure biexcitons. The two-quantum nonrephasing spectra provide direct evidence for unbound exciton pairs and biexcitons with dominantly attractive force. In addition, the spectral features of unbound exciton pairs show mixed absorptive and dispersive character, implying many-body interactions within the correlated Frenkel-exciton pairs. Our work offers novel perspectives on the Frenkel-exciton complexes in semiconductor polymers.
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Affiliation(s)
- Yulong Zheng
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United States
| | - Esteban Rojas-Gatjens
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United States
| | - Myeongyeon Lee
- Department
of Chemical & Biomolecular Engineering, Lehigh University, 124 E. Morton Street, Bethlehem, Pennsylvania 18015, United States
| | - Elsa Reichmanis
- Department
of Chemical & Biomolecular Engineering, Lehigh University, 124 E. Morton Street, Bethlehem, Pennsylvania 18015, United States
| | - Carlos Silva-Acuña
- School
of Chemistry and Biochemistry, Georgia Institute
of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332, United States
- Institut
Courtois & Département de physique, Université de Montréal, 1375 Avenue Thérèse-Lavoie-Roux, Montréal, Québec H2V 0B3, Canada
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3
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Brey D, Burghardt I. Coherent Transient Localization Mechanism of Interchain Exciton Transport in Regioregular P3HT: A Quantum-Dynamical Study. J Phys Chem Lett 2024; 15:1836-1845. [PMID: 38334949 DOI: 10.1021/acs.jpclett.3c03290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Transient localization has been proposed as a transport mechanism in organic materials, for both charge carriers and excitons. Here, we characterize a quantum coherent transient localization mechanism using full quantum simulations of an H-aggregated model system representative of regioregular poly(3-hexylthiophene) (rrP3HT). A Frenkel-Holstein Hamiltonian parametrized from first principles is considered, including local high-frequency modes and anharmonic, site-correlated interchain modes. Quantum-dynamical calculations are carried out using the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method for a 13-site system with 195 vibrational modes, under periodic boundary conditions. It is shown that temporary localization of exciton polarons alternates with resonant transfer driven by interchain modes. While the transport process is mainly determined by exciton-polarons at the low-energy band edge, persistent coupling with the excitonic manifold is observed, giving rise to a nonadiabatic excitonic flux. This elementary transport mechanism remains preserved for limited static disorder and gives way to Anderson localization when the static disorder becomes dominant.
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Affiliation(s)
- Dominik Brey
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
| | - Irene Burghardt
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt, Germany
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4
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Nagahara T, Camargo FVA, Xu F, Ganzer L, Russo M, Zhang P, Perri A, de la Cruz Valbuena G, Heisler IA, D’Andrea C, Polli D, Müllen K, Feng X, Mai Y, Cerullo G. Electronic Structure of Isolated Graphene Nanoribbons in Solution Revealed by Two-Dimensional Electronic Spectroscopy. NANO LETTERS 2024; 24:797-804. [PMID: 38189787 PMCID: PMC10811683 DOI: 10.1021/acs.nanolett.3c02665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 12/22/2023] [Accepted: 12/22/2023] [Indexed: 01/09/2024]
Abstract
Structurally well-defined graphene nanoribbons (GNRs) are nanostructures with unique optoelectronic properties. In the liquid phase, strong aggregation typically hampers the assessment of their intrinsic properties. Recently we reported a novel type of GNRs, decorated with aliphatic side chains, yielding dispersions consisting mostly of isolated GNRs. Here we employ two-dimensional electronic spectroscopy to unravel the optical properties of isolated GNRs and disentangle the transitions underlying their broad and rather featureless absorption band. We observe that vibronic coupling, typically neglected in modeling, plays a dominant role in the optical properties of GNRs. Moreover, a strong environmental effect is revealed by a large inhomogeneous broadening of the electronic transitions. Finally, we also show that the photoexcited bright state decays, on the 150 fs time scale, to a dark state which is in thermal equilibrium with the bright state, that remains responsible for the emission on nanosecond time scales.
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Affiliation(s)
- Tetsuhiko Nagahara
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
- Department
of Chemistry and Materials Technology, Kyoto
Institute of Technology, 606-8585 Kyoto, Japan
| | | | - Fugui Xu
- School
of Chemistry and Chemical Engineering, Frontiers Science Center for
Transformative Molecules, Shanghai Jiao
Tong University, 800 Dongchuan Rd, Shanghai 200240, China
| | - Lucia Ganzer
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Mattia Russo
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Pengfei Zhang
- School
of Chemistry and Chemical Engineering, Frontiers Science Center for
Transformative Molecules, Shanghai Jiao
Tong University, 800 Dongchuan Rd, Shanghai 200240, China
| | - Antonio Perri
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | | | - Ismael A. Heisler
- Departamento
de Física, Universidade Federal do
Paraná, Caixa
Postal 19044, 81531-990 Curitiba, Paraná, Brazil
| | - Cosimo D’Andrea
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Dario Polli
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
| | - Klaus Müllen
- Max Planck
Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Xinliang Feng
- Department
of Chemistry and Food Chemistry, Technische
Universität Dresden, Mommsenstrasse 4, 01062 Dresden, Germany
| | - Yiyong Mai
- School
of Chemistry and Chemical Engineering, Frontiers Science Center for
Transformative Molecules, Shanghai Jiao
Tong University, 800 Dongchuan Rd, Shanghai 200240, China
| | - Giulio Cerullo
- Dipartimento
di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy
- IFN-CNR, Piazza L. da Vinci 32, 20133 Milano, Italy
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5
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Tutunnikov I, Chuang C, Cao J. Coherent Spatial Control of Wave Packet Dynamics on Quantum Lattices. J Phys Chem Lett 2023; 14:11632-11639. [PMID: 38100722 DOI: 10.1021/acs.jpclett.3c03047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Quantum lattices are pivotal in the burgeoning fields of quantum materials and information science. Novel experimental techniques allow the preparation and monitoring of wave packet dynamics on quantum lattices with high spatiotemporal resolution. We present an analytical study of wave packet diffusivity and diffusion length on tight-binding quantum lattices subject to stochastic noise. Our analysis reveals the crucial role of spatial coherence and predicts a set of novel phenomena: (1) noise can enhance the transient diffusivity and diffusion length of spatially extended initial states; (2) standing or traveling initial states, with large momentum, spread faster than a localized initial state and exhibit a noise-induced peak in the transient diffusivity; (3) the differences in the diffusivity or diffusion length of extended and localized initial states have a universal dependence on initial width. These predictions suggest the possibility of controlling the wave packet dynamics by spatial manipulations, which will have implications for materials science and quantum technologies.
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Affiliation(s)
- Ilia Tutunnikov
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Chern Chuang
- Department of Chemistry and Biochemistry, University of Nevada, 4505 S Maryland Pkwy, Las Vegas, Nevada 89154, United States
| | - Jianshu Cao
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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6
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Rose PA, Krich JJ. Interpretations of High-Order Transient Absorption Spectroscopies. J Phys Chem Lett 2023; 14:10849-10855. [PMID: 38032056 DOI: 10.1021/acs.jpclett.3c02491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
Transient absorption (TA) spectroscopy is an invaluable tool for determining the energetics and dynamics of excited states. When pump intensities are sufficiently high, TA spectra include both the generally desired third-order response and responses that are higher in order in the field amplitudes. Recent work demonstrated that pump-intensity-dependent TA measurements allow separating the orders of response, but the information content in those higher orders has not been described. We give a general framework for understanding high-order TA spectra. We extend to higher order the fundamental processes of standard TA: ground-state bleach (GSB), stimulated emission (SE), and excited-state absorption (ESA). Each order introduces two new processes: SE and ESA from previously inaccessible highly excited states and negations of lower-order processes. We show the new spectral and dynamical information at each order and show how the relative signs of the signals in different orders can be used to identify which processes dominate.
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Affiliation(s)
- Peter A Rose
- Department of Physics, University of Ottawa, Ottawa ON K1N 6N5, Canada
| | - Jacob J Krich
- Department of Physics, University of Ottawa, Ottawa ON K1N 6N5, Canada
- Nexus for Quantum Technologies, University of Ottawa, Ottawa ON K1N 6N5, Canada
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7
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Lüttig J, Mueller S, Malý P, Krich JJ, Brixner T. Higher-Order Multidimensional and Pump-Probe Spectroscopies. J Phys Chem Lett 2023; 14:7556-7573. [PMID: 37589504 DOI: 10.1021/acs.jpclett.3c01694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
Transient absorption and coherent two-dimensional spectroscopy are widely established methods for the investigation of ultrafast dynamics in quantum systems. Conventionally, they are interpreted in the framework of perturbation theory at the third order of interaction. Here, we discuss the potential of higher-(than-third-)order pump-probe and multidimensional spectroscopy to provide insight into excited multiparticle states and their dynamics. We focus on recent developments from our group. In particular, we demonstrate how phase cycling can be used in fluorescence-detected two-dimensional spectroscopy to isolate higher-order spectra that provide information about highly excited states such as the correlation of multiexciton states. We discuss coherently detected fifth-order 2D spectroscopy and its power to track exciton diffusion. Finally, we show how to extract higher-order signals even from ordinary pump-probe experiments, providing annihilation-free signals at high excitation densities and insight into multiexciton interactions.
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Affiliation(s)
- Julian Lüttig
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Stefan Mueller
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague, Czech Republic
| | - Jacob J Krich
- Department of Physics, University of Ottawa, Ottawa K1N 6N5, Canada
- School of Electrical Engineering and Computer Science, University of Ottawa, Ottawa K1N 6N5, Canada
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
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8
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Lüttig J, Rose PA, Malý P, Turkin A, Bühler M, Lambert C, Krich JJ, Brixner T. High-order pump-probe and high-order two-dimensional electronic spectroscopy on the example of squaraine oligomers. J Chem Phys 2023; 158:234201. [PMID: 37326161 DOI: 10.1063/5.0139090] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 03/06/2023] [Indexed: 06/17/2023] Open
Abstract
Time-resolved spectroscopy is commonly used to study diverse phenomena in chemistry, biology, and physics. Pump-probe experiments and coherent two-dimensional (2D) spectroscopy have resolved site-to-site energy transfer, visualized electronic couplings, and much more. In both techniques, the lowest-order signal, in a perturbative expansion of the polarization, is of third order in the electric field, which we call a one-quantum (1Q) signal because in 2D spectroscopy it oscillates in the coherence time with the excitation frequency. There is also a two-quantum (2Q) signal that oscillates in the coherence time at twice the fundamental frequency and is fifth order in the electric field. We demonstrate that the appearance of the 2Q signal guarantees that the 1Q signal is contaminated by non-negligible fifth-order interactions. We derive an analytical connection between an nQ signal and (2n + 1)th-order contaminations of an rQ (with r < n) signal by studying Feynman diagrams of all contributions. We demonstrate that by performing partial integrations along the excitation axis in 2D spectra, we can obtain clean rQ signals free of higher-order artifacts. We exemplify the technique using optical 2D spectroscopy on squaraine oligomers, showing clean extraction of the third-order signal. We further demonstrate the analytical connection with higher-order pump-probe spectroscopy and compare both techniques experimentally. Our approach demonstrates the full power of higher-order pump-probe and 2D spectroscopy to investigate multi-particle interactions in coupled systems.
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Affiliation(s)
- Julian Lüttig
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Peter A Rose
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
| | - Arthur Turkin
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Michael Bühler
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
| | - Jacob J Krich
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
- School of Electrical Engineering and Computer Science, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
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9
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Malý P, Lüttig J, Rose PA, Turkin A, Lambert C, Krich JJ, Brixner T. Separating single- from multi-particle dynamics in nonlinear spectroscopy. Nature 2023; 616:280-287. [PMID: 36973449 DOI: 10.1038/s41586-023-05846-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 02/15/2023] [Indexed: 03/29/2023]
Abstract
Quantum states depend on the coordinates of all their constituent particles, with essential multi-particle correlations. Time-resolved laser spectroscopy1 is widely used to probe the energies and dynamics of excited particles and quasiparticles such as electrons and holes2,3, excitons4-6, plasmons7, polaritons8 or phonons9. However, nonlinear signals from single- and multiple-particle excitations are all present simultaneously and cannot be disentangled without a priori knowledge of the system4,10. Here, we show that transient absorption-the most commonly used nonlinear spectroscopy-with N prescribed excitation intensities allows separation of the dynamics into N increasingly nonlinear contributions; in systems well-described by discrete excitations, these N contributions systematically report on zero to N excitations. We obtain clean single-particle dynamics even at high excitation intensities and can systematically increase the number of interacting particles, infer their interaction energies and reconstruct their dynamics, which are not measurable via conventional means. We extract single- and multiple-exciton dynamics in squaraine polymers11,12 and, contrary to common assumption6,13, we find that the excitons, on average, meet several times before annihilating. This surprising ability of excitons to survive encounters is important for efficient organic photovoltaics14,15. As we demonstrate on five diverse systems, our procedure is general, independent of the measured system or type of observed (quasi)particle and straightforward to implement. We envision future applicability in the probing of (quasi)particle interactions in such diverse areas as plasmonics7, Auger recombination2 and exciton correlations in quantum dots5,16,17, singlet fission18, exciton interactions in two-dimensional materials19 and in molecules20,21, carrier multiplication22, multiphonon scattering9 or polariton-polariton interaction8.
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Affiliation(s)
- Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Würzburg, Germany.
- Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
| | - Julian Lüttig
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Würzburg, Germany
| | - Peter A Rose
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada
| | - Arthur Turkin
- Institut für Organische Chemie, Universität Würzburg, Würzburg, Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Universität Würzburg, Würzburg, Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Würzburg, Germany
| | - Jacob J Krich
- Department of Physics, University of Ottawa, Ottawa, Ontario, Canada.
- School of Electrical Engineering and Computer Science, University of Ottawa, Ottawa, Ontario, Canada.
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Würzburg, Germany.
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Würzburg, Germany.
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10
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Kalra A, Benny A, Travis SM, Zizzi EA, Morales-Sanchez A, Oblinsky DG, Craddock TJA, Hameroff SR, MacIver MB, Tuszyński JA, Petry S, Penrose R, Scholes GD. Electronic Energy Migration in Microtubules. ACS CENTRAL SCIENCE 2023; 9:352-361. [PMID: 36968538 PMCID: PMC10037452 DOI: 10.1021/acscentsci.2c01114] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Indexed: 05/29/2023]
Abstract
The repeating arrangement of tubulin dimers confers great mechanical strength to microtubules, which are used as scaffolds for intracellular macromolecular transport in cells and exploited in biohybrid devices. The crystalline order in a microtubule, with lattice constants short enough to allow energy transfer between amino acid chromophores, is similar to synthetic structures designed for light harvesting. After photoexcitation, can these amino acid chromophores transfer excitation energy along the microtubule like a natural or artificial light-harvesting system? Here, we use tryptophan autofluorescence lifetimes to probe energy hopping between aromatic residues in tubulin and microtubules. By studying how the quencher concentration alters tryptophan autofluorescence lifetimes, we demonstrate that electronic energy can diffuse over 6.6 nm in microtubules. We discover that while diffusion lengths are influenced by tubulin polymerization state (free tubulin versus tubulin in the microtubule lattice), they are not significantly altered by the average number of protofilaments (13 versus 14). We also demonstrate that the presence of the anesthetics etomidate and isoflurane reduce exciton diffusion. Energy transport as explained by conventional Förster theory (accommodating for interactions between tryptophan and tyrosine residues) does not sufficiently explain our observations. Our studies indicate that microtubules are, unexpectedly, effective light harvesters.
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Affiliation(s)
- Aarat
P. Kalra
- Department
of Chemistry, New Frick Chemistry Building, Princeton University, Princeton, New Jersey08544, United States
| | - Alfy Benny
- Department
of Chemistry, New Frick Chemistry Building, Princeton University, Princeton, New Jersey08544, United States
| | - Sophie M. Travis
- Department
of Molecular Biology, Schultz Laboratory, Princeton University, Princeton, New Jersey08544, United States
| | - Eric A. Zizzi
- Department
of Mechanical and Aerospace Engineering (DIMEAS), Politecnico di Torino, Torino10129, Italy
| | - Austin Morales-Sanchez
- Department
of Chemistry, New Frick Chemistry Building, Princeton University, Princeton, New Jersey08544, United States
| | - Daniel G. Oblinsky
- Department
of Chemistry, New Frick Chemistry Building, Princeton University, Princeton, New Jersey08544, United States
| | - Travis J. A. Craddock
- Departments
of Psychology & Neuroscience, Computer Science, and Clinical Immunology, Nova Southeastern University, Ft. Lauderdale, Florida33314, United States
| | - Stuart R. Hameroff
- Department
of Anesthesiology, Center for Consciousness Studies, University of Arizona, Tucson, Arizona85721, United States
| | - M. Bruce MacIver
- Department
of Anesthesiology, Stanford University School
of Medicine, Stanford, California94305, United States
| | - Jack A. Tuszyński
- Department
of Mechanical and Aerospace Engineering (DIMEAS), Politecnico di Torino, Torino10129, Italy
- Department
of Physics, University of Alberta, Edmonton, AlbertaT6G 2E1, Canada
- Department
of Oncology, University of Alberta, Edmonton, AlbertaT6G 1Z2, Canada
| | - Sabine Petry
- Department
of Molecular Biology, Schultz Laboratory, Princeton University, Princeton, New Jersey08544, United States
| | - Roger Penrose
- Mathematical
Institute, Andrew Wiles Building, University
of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford, OX2 6GG, United
Kingdom
| | - Gregory D. Scholes
- Department
of Chemistry, New Frick Chemistry Building, Princeton University, Princeton, New Jersey08544, United States
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11
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Wright N, Huff JS, Barclay MS, Wilson CK, Barcenas G, Duncan KM, Ketteridge M, Obukhova OM, Krivoshey AI, Tatarets AL, Terpetschnig EA, Dean JC, Knowlton WB, Yurke B, Li L, Mass OA, Davis PH, Lee J, Turner DB, Pensack RD. Intramolecular Charge Transfer and Ultrafast Nonradiative Decay in DNA-Tethered Asymmetric Nitro- and Dimethylamino-Substituted Squaraines. J Phys Chem A 2023; 127:1141-1157. [PMID: 36705555 PMCID: PMC9923757 DOI: 10.1021/acs.jpca.2c06442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Molecular (dye) aggregates are a materials platform of interest in light harvesting, organic optoelectronics, and nanoscale computing, including quantum information science (QIS). Strong excitonic interactions between dyes are key to their use in QIS; critically, properties of the individual dyes govern the extent of these interactions. In this work, the electronic structure and excited-state dynamics of a series of indolenine-based squaraine dyes incorporating dimethylamino (electron donating) and/or nitro (electron withdrawing) substituents, so-called asymmetric dyes, were characterized. The dyes were covalently tethered to DNA Holliday junctions to suppress aggregation and permit characterization of their monomer photophysics. A combination of density functional theory and steady-state absorption spectroscopy shows that the difference static dipole moment (Δd) successively increases with the addition of these substituents while simultaneously maintaining a large transition dipole moment (μ). Steady-state fluorescence and time-resolved absorption and fluorescence spectroscopies uncover a significant nonradiative decay pathway in the asymmetrically substituted dyes that drastically reduces their excited-state lifetime (τ). This work indicates that Δd can indeed be increased by functionalizing dyes with electron donating and withdrawing substituents and that, in certain classes of dyes such as these asymmetric squaraines, strategies may be needed to ensure long τ, e.g., by rigidifying the π-conjugated network.
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Affiliation(s)
- Nicholas
D. Wright
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Jonathan S. Huff
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Matthew S. Barclay
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Christopher K. Wilson
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - German Barcenas
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Katelyn M. Duncan
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Maia Ketteridge
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Olena M. Obukhova
- SSI
“Institute for Single Crystals” of the National Academy
of Sciences of Ukraine, Kharkiv 61072, Ukraine
| | - Alexander I. Krivoshey
- SSI
“Institute for Single Crystals” of the National Academy
of Sciences of Ukraine, Kharkiv 61072, Ukraine
| | - Anatoliy L. Tatarets
- SSI
“Institute for Single Crystals” of the National Academy
of Sciences of Ukraine, Kharkiv 61072, Ukraine
| | | | - Jacob C. Dean
- Department
of Physical Science, Southern Utah University, Cedar City, Utah 84720, United States
| | - William B. Knowlton
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Bernard Yurke
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Lan Li
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States,Center
for
Advanced Energy Studies, Idaho
Falls, Idaho 83401, United States
| | - Olga A. Mass
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Paul H. Davis
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States,Center
for
Advanced Energy Studies, Idaho
Falls, Idaho 83401, United States
| | - Jeunghoon Lee
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Daniel B. Turner
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States
| | - Ryan D. Pensack
- †Micron
School of Materials Science & Engineering, ⊥Department of Electrical
& Computer Engineering, ○Department of Chemistry & Biochemistry, Boise State University, Boise, Idaho 83725, United States,
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12
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Jayachandran A, Mueller S, Brixner T. Fluorescence-Detected Two-Quantum Photon Echoes via Cogwheel Phase Cycling. J Phys Chem Lett 2022; 13:11710-11719. [PMID: 36512681 DOI: 10.1021/acs.jpclett.2c03372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Two-dimensional (2D) electronic spectroscopy can separate homogeneous and inhomogeneous broadening. While established methods usually probe a photon-echo signal, i.e., a third-order response, to access the homogeneous line width of singly excited states, the homogeneous line width of doubly excited states remained spectroscopically inaccessible. Here we demonstrate the acquisition of two-quantum (2Q) photon echoes using fluorescence-detected 2D spectroscopy. In these eighth-order signals, 2Q coherences are rephased with themselves, leading to line-narrowed 2Q-2Q 2D spectra. By using cogwheel phase cycling, adapted from nuclear magnetic resonance spectroscopy, we isolate the 2Q-2Q 2D spectra of a squaraine dimer and a squaraine polymer and verify the same selectivity of cogwheel phase cycling compared to traditional "nested" phase cycling. The observed difference, between the two systems, in the homogeneous line width of the biexciton can be rationalized as a signature of the interplay of exciton-exciton annihilation, exciton diffusion, and exciton delocalization.
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Affiliation(s)
- Ajay Jayachandran
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Stefan Mueller
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
- Center for Nanosystems Chemistry (CNC), Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany
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13
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Timmer D, Zheng F, Gittinger M, Quenzel T, Lünemann DC, Winte K, Zhang Y, Madjet ME, Zablocki J, Lützen A, Zhong JH, De Sio A, Frauenheim T, Tretiak S, Lienau C. Charge Delocalization and Vibronic Couplings in Quadrupolar Squaraine Dyes. J Am Chem Soc 2022; 144:19150-19162. [PMID: 36206456 DOI: 10.1021/jacs.2c08682] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Squaraines are prototypical quadrupolar charge-transfer chromophores that have recently attracted much attention as building blocks for solution-processed photovoltaics, fluorescent probes with large two-photon absorption cross sections, and aggregates with large circular dichroism. Their optical properties are often rationalized in terms of phenomenological essential state models, considering the coupling of two zwitterionic excited states to a neutral ground state. As a result, optical transitions to the lowest S1 excited state are one-photon allowed, whereas the next higher S2 state can only be accessed by two-photon transitions. A further implication of these models is a substantial reduction of vibronic coupling to the ubiquitous high-frequency vinyl-stretching modes of organic materials. Here, we combine time-resolved vibrational spectroscopy, two-dimensional electronic spectroscopy, and quantum-chemical simulations to test and rationalize these predictions for nonaggregated molecules. We find small Huang-Rhys factors below 0.01 for the high-frequency, 1500 cm-1 modes in particular, as well as a noticeable reduction for those of lower frequency modes in general for the electronic S0 → S1 transition. The two-photon allowed state S2 is well separated energetically from S1 and has weak vibronic signatures as well. Thus, the resulting pronounced concentration of the oscillator strength in a narrow region relevant to the lowest electronic transition makes squaraines and their aggregates exceptionally interesting for strong and ultrastrong coupling of excitons to localized light modes in external resonators with chiral properties that can largely be controlled by the molecular architecture.
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Affiliation(s)
- Daniel Timmer
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Fulu Zheng
- Bremen Center for Computational Materials Science, University of Bremen, Bremen28359, Germany
| | - Moritz Gittinger
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Thomas Quenzel
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Daniel C Lünemann
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Katrin Winte
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Yu Zhang
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico87545, United States
| | - Mohamed E Madjet
- Bremen Center for Computational Materials Science, University of Bremen, Bremen28359, Germany
| | - Jennifer Zablocki
- Kekulé-Institute for Organic Chemistry and Biochemistry, University of Bonn, Bonn53121, Germany
| | - Arne Lützen
- Kekulé-Institute for Organic Chemistry and Biochemistry, University of Bonn, Bonn53121, Germany
| | - Jin-Hui Zhong
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany.,Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong518055, China
| | - Antonietta De Sio
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany.,Center for Nanoscale Dynamics (CeNaD), Carl von Ossietzky Universität, Oldenburg26129, Germany
| | - Thomas Frauenheim
- Bremen Center for Computational Materials Science, University of Bremen, Bremen28359, Germany.,Beijing Computational Science Research Center (CSRC), Beijing100193, China.,Shenzhen Computational Science and Applied Research (CSAR) Institute, Shenzhen518110, China
| | - Sergei Tretiak
- Theoretical Division and Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico87545, United States
| | - Christoph Lienau
- Institut für Physik, Carl von Ossietzky Universität, Oldenburg26129, Germany.,Center for Nanoscale Dynamics (CeNaD), Carl von Ossietzky Universität, Oldenburg26129, Germany.,Forschungszentrum Neurosensorik, Carl von Ossietzky Universität, Oldenburg26129, Germany
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14
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Alban-Chacón FE, Lamilla-Rubio EA, Alvarez-Alvarado MS. A Novel Physical Mechanism to Model Brownian Yet Non-Gaussian Diffusion: Theory and Application. MATERIALS (BASEL, SWITZERLAND) 2022; 15:5808. [PMID: 36079190 PMCID: PMC9457340 DOI: 10.3390/ma15175808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/23/2022] [Accepted: 08/17/2022] [Indexed: 06/15/2023]
Abstract
In the last years, a few experiments in the fields of biological and soft matter physics in colloidal suspensions have reported "normal diffusion" with a Laplacian probability distribution in the particle's displacements (i.e., Brownian yet non-Gaussian diffusion). To model this behavior, different stochastic and microscopic models have been proposed, with the former introducing new random elements that incorporate our lack of information about the media and the latter describing a limited number of interesting physical scenarios. This incentivizes the search of a more thorough understanding of how the media interacts with itself and with the particle being diffused in Brownian yet non-Gaussian diffusion. For this reason, a comprehensive mathematical model to explain Brownian yet non-Gaussian diffusion that includes weak molecular interactions is proposed in this paper. Based on the theory of interfaces by De Gennes and Langevin dynamics, it is shown that long-range interactions in a weakly interacting fluid at shorter time scales leads to a Laplacian probability distribution in the radial particle's displacements. Further, it is shown that a phase separation can explain a high diffusivity and causes this Laplacian distribution to evolve towards a Gaussian via a transition probability in the interval of time as it was observed in experiments. To verify these model predictions, the experimental data of the Brownian motion of colloidal beads on phospholipid bilayer by Wang et al. are used and compared with the results of the theory. This comparison suggests that the proposed model is able to explain qualitatively and quantitatively the Brownian yet non-Gaussian diffusion.
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Affiliation(s)
- Francisco E. Alban-Chacón
- Faculty of Natural Science and Mathematics, Escuela Superior Politécnica del Litoral, Guayaquil 090112, Ecuador
| | - Erick A. Lamilla-Rubio
- Faculty of Natural Science and Mathematics, Escuela Superior Politécnica del Litoral, Guayaquil 090112, Ecuador
- Facultad de Ciencias Matemáticas y Físicas, Universidad de Guayaquil, Guayaquil 090514, Ecuador
| | - Manuel S. Alvarez-Alvarado
- Faculty of Natural Science and Mathematics, Escuela Superior Politécnica del Litoral, Guayaquil 090112, Ecuador
- Faculty of Electrical and Computer Engineering, Escuela Superior Politécnica del Litoral, Guayaquil 090112, Ecuador
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15
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Mondelo-Martell M, Brey D, Burghardt I. Quantum dynamical study of inter-chain exciton transport in a regioregular P3HT model system at finite temperature: HJ vs. H-aggregate models. J Chem Phys 2022; 157:094108. [DOI: 10.1063/5.0104729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report on quantum dynamical simulations of inter-chain exciton transport in a model of regioregular poly(3-hexylthiophene), rr-P3HT, at finite temperature, using the Multi-Layer Multi-Configuration Time-Dependent Hartree (ML-MCTDH) method for a system of up to 63 electronic states and 180 vibrational modes. A Frenkel Hamiltonian of HJ aggregate type is used, along with a reduced H-aggregate representation; electron-phonon coupling includes local high-frequency modes as well as anharmonic intermolecular modes. The latter are operative in mediating inter-chain transport, by a mechanism of transient localization type. Strikingly, this mechanism is found to be of quantum coherent character and involves non-adiabatic effects. Using periodic boundary conditions, a normal diffusion regime is identified from the exciton mean-squared displacement, apart from early-time transients. Diffusion coefficients are found to be of the order of 3 x 10-3 cm2/s, showing a non-monotonous increase with temperature.
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Affiliation(s)
- Manel Mondelo-Martell
- Institut für Physikalische u. Theoretische Chemie, Goethe-Universitat Frankfurt am Main Institut fur Physikalische und Theoretische Chemie, Germany
| | | | - Irene Burghardt
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt, Germany
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16
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Farrell KM, Zanni MT. Phase stable, shot-to-shot measurement of third- and fifth-order two-quantum correlation spectra using a pulse shaper in the pump-probe geometry. J Chem Phys 2022; 157:014203. [PMID: 35803806 PMCID: PMC9262413 DOI: 10.1063/5.0097019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We demonstrate the first phase stable measurement of a third-order 2Q spectrum using a pulse shaper in the pump-probe geometry. This measurement was achieved by permuting the time-ordering of the pump pulses, thus rearranging the signal pathways that are emitted in the probe direction. The third-order 2Q spectrum is self-heterodyned by the probe pulse. Using this method, one can interconvert between a 1Q experiment and a 2Q experiment by simply reprogramming a pulse shaper or delay stage. We also measure a fifth-order absorptive 2Q spectrum in the pump-probe geometry, which contains similar information as a third-order experiment but does not suffer from dispersive line shapes. To do so, we introduce methods to minimize saturation-induced artifacts of the pulse shaper, improving fifth-order signals. These techniques add new capabilities for 2D spectrometers that use pulse shapers in the pump-probe beam geometry.
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Affiliation(s)
- Kieran M Farrell
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Martin T Zanni
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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17
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Heshmatpour C, Hauer J, Šanda F. Correlated spectral fluctuations quantified by line shape analysis of fifth-order two-dimensional electronic spectra. J Chem Phys 2022; 156:084114. [DOI: 10.1063/5.0081053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Correlated spectral fluctuations were suggested to coordinate excitation transport inside natural light harvesting complexes. We demonstrate the capacities of 2D line shapes from fifth-order coherent electronic signals (R5-2D) to report on such fluctuations in molecular aggregates and present a stochastic approach to fluctuations in correlated site and bi-exciton binding energies in the optical dynamics of Frenkel excitons. The model is applied to R5-2D line shapes of a homodimer, and we show that the peak tilt dynamics are a measure for site energy disorder, inter-site correlation, and the strength of bi-exciton binding energy fluctuations.
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Affiliation(s)
- Constantin Heshmatpour
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 121 16, Czech Republic
- Professur für Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstr. 4, D-85748 Garching b. München, Germany
| | - Jürgen Hauer
- Professur für Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstr. 4, D-85748 Garching b. München, Germany
| | - František Šanda
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 121 16, Czech Republic
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18
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Brey D, Binder R, Martinazzo R, Burghardt I. Signatures of coherent vibronic exciton dynamics and conformational control in two-dimensional electronic spectroscopy of conjugated polymers. Faraday Discuss 2022; 237:148-167. [DOI: 10.1039/d2fd00014h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two-dimensional electronic spectroscopy (2DES) signals for homo-oligomer J-aggregates are computed, with a focus on the role of structural change induced by low-frequency torsional modes along with quasi-stationary trapping effects induced...
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19
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Glaab F, Süβ J, Engel V. Third-order pump-probe spectroscopy applied to molecular dimers: characterization of relaxation dynamics and exciton–exciton annihilation. Phys Chem Chem Phys 2022; 24:25316-25326. [DOI: 10.1039/d2cp03435b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Exciton–exciton annihilation in a dimer, described within the basis of localizes monomer states.
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Affiliation(s)
- Fabian Glaab
- Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - Jasmin Süβ
- Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - Volker Engel
- Universität Würzburg, Institut für Physikalische und Theoretische Chemie, Emil-Fischer-Str. 42, 97074 Würzburg, Germany
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20
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Turkin A, Malý P, Lambert C. Fluorescence band exchange narrowing in a series of squaraine oligomers: energetic vs. structural disorder. Phys Chem Chem Phys 2021; 23:18393-18403. [PMID: 34612380 DOI: 10.1039/d1cp02136b] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The influence of oligosquaraine chain length on the energies and shape of absorption and emission bands and the exciton coherence length is studied in CHCl3 where the oligomers adopt a random coil structure. From the observed fluorescence band narrowing an effective coherence length of Ncoh = 2.5 was estimated for the nonamer. Applying a theoretical Frenkel exciton model the absorption and emission spectra were simulated which confirmed the experimental results. From the relative amplitude of the 00 peak to the vibronic shoulder the coherence length was estimated which yields a somewhat higher saturation value of Ncoh≈ 3 for the nonamer, which is in very good agreement with the theoretical amplitude ratio. The coherence length is much smaller than the geometrical length because the electronic delocalisation is reduced by structural disorder. Taking into account the energetic (diagonal) and structural (off-diagonal) disorder we observed a different influence on the absorption and fluorescence spectra. For the emission spectra, exciton delocalisation leads to a narrowing of the band caused by averaging over energetic disorder, but for the absorption band the spectra are broadened by excitonic splitting and structural disorder.
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Affiliation(s)
- Arthur Turkin
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.
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21
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Chuang C, Cao J. Universal Scalings in Two-Dimensional Anisotropic Dipolar Excitonic Systems. PHYSICAL REVIEW LETTERS 2021; 127:047402. [PMID: 34355927 DOI: 10.1103/physrevlett.127.047402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 12/28/2020] [Accepted: 06/23/2021] [Indexed: 06/13/2023]
Abstract
Low-dimensional excitonic materials have inspired much interest owing to their novel physical and technological prospects. In particular, those with strong in-plane anisotropy are among the most intriguing but short of general analyses. We establish the universal functional form of the anisotropic dispersion in the small k limit for 2D dipolar excitonic systems. While the energy is linearly dispersed in the direction parallel to the dipole in plane, the perpendicular direction is dispersionless up to linear order, which can be explained by the quantum interference effect of the interaction among the constituents of 1D subsystems. The anisotropic dispersion results in a E^{∼0.5} scaling of the system density of states and predicts unique spectroscopic signatures including: (1) disorder-induced absorption linewidth, W(σ)∼σ^{2.8}, with σ the disorder strength, (2) temperature dependent absorption linewidth, W(T)∼T^{s+1.5}, with s the exponent of the environment spectral density, and (3) the out-of-plane angular θ dependence of the peak splittings in absorption spectra, ΔE(θ)∝sin^{2}θ. These predictions are confirmed quantitatively with numerical simulations of molecular thin films and tubules.
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Affiliation(s)
- Chern Chuang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jianshu Cao
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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22
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Lüttig J, Brixner T, Malý P. Anisotropy in fifth-order exciton-exciton-interaction two-dimensional spectroscopy. J Chem Phys 2021; 154:154202. [PMID: 33887932 DOI: 10.1063/5.0046894] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Exciton-exciton-interaction two-dimensional (EEI2D) spectroscopy is a fifth-order variant of 2D electronic spectroscopy. It can be used to probe biexciton dynamics in molecular systems and to observe exciton diffusion in extended systems such as polymers or light-harvesting complexes. The exciton transport strongly depends on the geometrical and energetic landscape and its perturbations. These can be of both local character, such as molecular orientation and energetic disorder, and long-range character, such as polymer kinks and structural domains. In the present theoretical work, we investigate the anisotropy in EEI2D spectroscopy. We introduce a general approach for how to calculate the anisotropy by using the response-function formalism in an efficient way. In numerical simulations, using a Frenkel exciton model with Redfield-theory dynamics, we demonstrate how the measurement of anisotropy in EEI2D spectroscopy can be used to identify various geometrical effects on exciton transport in dimers and polymers. Investigating a molecular heterodimer as an example, we demonstrate the utility of anisotropy in EEI2D spectroscopy for disentangling dynamic localization and annihilation. We further calculate the annihilation in extended systems such as conjugated polymers. In a polymer, a change in the anisotropy provides a unique signature for exciton transport between differently oriented sections. We analyze three types of geometry variations in polymers: a kink, varying geometric and energetic disorder, and different geometric domains. Our findings underline that employing anisotropy in EEI2D spectroscopy provides a way to distinguish between different geometries and can be used to obtain a better understanding of long-range exciton transport.
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Affiliation(s)
- Julian Lüttig
- Institut für Physikalische und Theoretische Chemie, Am Hubland, 97074 Würzburg, Germany
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Am Hubland, 97074 Würzburg, Germany
| | - Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Am Hubland, 97074 Würzburg, Germany
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23
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Lambert C, Hoche J, Schreck MH, Holzapfel M, Schmiedel A, Selby J, Turkin A, Mitric R. Ultrafast Energy Transfer Dynamics in a Squaraine Heterotriad. J Phys Chem A 2021; 125:2504-2511. [PMID: 33739846 DOI: 10.1021/acs.jpca.1c00349] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A squaraine heterotriad consisting of three different covalently linked squaraine chromophores was synthesized, and its absorption spectra were interpreted in terms of Kasha's exciton coupling theory. Using the exciton couplings derived from model dyads (ca. 700 cm-1) as the input, we were able to predict the exciton state energies of the heterotriad. Transient absorption spectroscopy with femtosecond time resolution showed that excitation of the highest exciton state populates a state mainly localized at one terminal squaraine chromophore, and energy transfer to the lowest exciton state localized at the other terminal squaraine occurs within 30 fs. Field-induced surface hopping dynamics simulations support the assumption of ultrafast energy transfer. Moreover, they show the close relationship between internal conversion and energy transfer in the intermediate to weak coupling regime. The latter is a consequence of excitation localization caused by molecular vibrations.
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Affiliation(s)
- Christoph Lambert
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.,Center for Nanosystems Chemistry, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Joscha Hoche
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Maximilian H Schreck
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Marco Holzapfel
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Alexander Schmiedel
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Joshua Selby
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Arthur Turkin
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Roland Mitric
- Center for Nanosystems Chemistry, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany.,Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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24
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Brosseau P, Palato S, Seiler H, Baker H, Kambhampati P. Fifth-order two-quantum absorptive two-dimensional electronic spectroscopy of CdSe quantum dots. J Chem Phys 2020; 153:234703. [PMID: 33353320 DOI: 10.1063/5.0021381] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Two-quantum variants of two-dimensional electronic spectroscopy (2DES) have previously been used to characterize multi-exciton interactions in molecules and semiconductor nanostructures though many implementations are limited by phasing procedures or non-resonant signals. We implement 2DES using phase-cycling to simultaneously measure one-quantum and two-quantum spectra in colloidal CdSe quantum dots. In the pump-probe geometry, fully absorptive spectra are automatically acquired by measuring the sum of the rephasing and nonrephasing signals. Fifth-order two-quantum spectroscopy allows for direct access to multi-exciton states that may be obscured in excited state absorption signals due to population relaxation or third-order two-quantum spectra due to the non-resonant response.
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Affiliation(s)
- Patrick Brosseau
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Samuel Palato
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Hélène Seiler
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
| | - Harry Baker
- Department of Chemistry, McGill University, Montreal, Quebec H3A 0B8, Canada
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25
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Süß J, Engel V. Exciton-exciton annihilation in a molecular trimer: Wave packet dynamics and 2D spectroscopy. J Chem Phys 2020; 153:164310. [PMID: 33138437 DOI: 10.1063/5.0027837] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We theoretically study the exciton-exciton annihilation (EEA) in a molecular trimer MMM. The system is treated within a model of electronic states, and the coupling to a bath is incorporated using the quantum jump method. Two situations of initial excitation are compared. In the first one, a two-photon process populates configurations M*M*M and MM*M* so that two excitons reside on neighboring monomers M. Then, EEA can immediately proceed. In contrast, if the trimer initially is in the local configuration M*MM*, exciton diffusion must occur before the annihilation process can take place. For the trimer, this excitonic motion takes place on a very short time scale. In both cases, wave packets are prepared which show a different quantum dynamics where the latter depends on the couplings and decay rates. It is documented how fifth-order coherent two-dimensional spectroscopy can be used to directly map the EEA as a function of time.
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Affiliation(s)
- J Süß
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany
| | - V Engel
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Emil-Fischer-Str. 42, 97074 Würzburg, Germany
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Malý P, Mueller S, Lüttig J, Lambert C, Brixner T. Signatures of exciton dynamics and interaction in coherently and fluorescence-detected four- and six-wave-mixing two-dimensional electronic spectroscopy. J Chem Phys 2020; 153:144204. [PMID: 33086839 DOI: 10.1063/5.0022743] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Two-dimensional electronic spectroscopy (2DES) can be realized in increasing nonlinear orders of interaction with the electric field, bringing new information about single- and multi-particle properties and dynamics. Furthermore, signals can be detected both coherently (C-2DES) and by fluorescence (F-2DES), with fundamental and practical differences. We directly compare the simultaneous measurements of four- and six-wave mixing C-2DES and F-2DES on an excitonic heterodimer of squaraine molecules. Spectral features are described in increasing orders of nonlinearity by an explicit excitonic model. We demonstrate that the four-wave-mixing spectra are sensitive to one-exciton energies, their delocalization and dynamics, while the six-wave-mixing spectra include information on bi-exciton and higher excited states including the state energies, electronic coupling, and exciton-exciton annihilation. We focus on the possibility to extract the dynamics arising from exciton-exciton interaction directly from the six-wave-mixing spectra. To this end, in analogy to previously demonstrated fifth-order coherently detected exciton-exciton-interaction 2DES (EEI2D spectroscopy), we introduce a sixth-order fluorescence-detected EEI2D spectroscopy variant.
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Affiliation(s)
- Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Stefan Mueller
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Julian Lüttig
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Christoph Lambert
- Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Tobias Brixner
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
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Heshmatpour C, Malevich P, Plasser F, Menger M, Lambert C, Šanda F, Hauer J. Annihilation Dynamics of Molecular Excitons Measured at a Single Perturbative Excitation Energy. J Phys Chem Lett 2020; 11:7776-7781. [PMID: 32842744 DOI: 10.1021/acs.jpclett.0c02141] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Exciton-exciton annihilation (EEA) is a ubiquitous phenomenon, which may limit the efficiency of photovoltaic devices. Conventional methods of determining EEA time scales rely on measuring the intensity dependence of third-order signals. In this work, we directly extract the annihilation rate of molecular excitons in a covalently joined molecular trimer without the need to perform and analyze intensity dependent data by employing fifth-order coherent optical spectroscopy signals emitted into ±2k⃗1 ∓ 2k⃗2 + k⃗3 phase matching directions. Measured two-dimensional line shapes and their time traces are analyzed in the framework of the many-body version of the Frenkel exciton model, extended to incorporate annihilation dynamics. Combining double-sided Feynman diagrams with explicit simulations of the fifth-order response, we identify a single peak as a direct reporter of EEA. We retrieve an annihilation time of 30 fs for the investigated squaraine trimer.
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Affiliation(s)
- C Heshmatpour
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 121 16, Czech Republic
- Professur für Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85748, Garching b. München, Germany
| | - P Malevich
- Professur für Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85748, Garching b. München, Germany
| | - F Plasser
- Department of Chemistry, Loughborough University, Loughborough LE11 3TU, United Kingdom
| | - M Menger
- Faculty of Science and Engineering, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - C Lambert
- Institut für Organische Chemie, Center for Nanosystems Chemistry, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - F Šanda
- Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 121 16, Czech Republic
| | - J Hauer
- Professur für Dynamische Spektroskopien, Fakultät für Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85748, Garching b. München, Germany
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Hegger R, Binder R, Burghardt I. First-Principles Quantum and Quantum-Classical Simulations of Exciton Diffusion in Semiconducting Polymer Chains at Finite Temperature. J Chem Theory Comput 2020; 16:5441-5455. [PMID: 32786907 DOI: 10.1021/acs.jctc.0c00351] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
We report on first-principles quantum-dynamical and quantum-classical simulations of photoinduced exciton dynamics in oligothiophene chain segments, representative of intrachain exciton migration in the poly(3-hexylthiophene) (P3HT) polymer. Following up on our recent study (Binder R.; Burghardt, I. Faraday Discuss. 2020, 221, 406), multilayer multiconfiguration time-dependent Hartree calculations for a short oligothiophene segment comprising 20 monomer units (OT-20) are carried out to obtain full quantum-dynamical simulations at finite temperature. These are employed to benchmark mean-field Ehrenfest calculations, which are shown to give qualitatively correct results for the present system. Periodic boundary conditions turn out to significantly improve earlier estimates of diffusion coefficients. Using the Ehrenfest approach, a series of calculations are subsequently carried out for larger lattices (OT-40 to OT-80), leading to estimates for temperature-dependent mean-squared displacements, which are found to exhibit a near-linear dependence as a function of time. The resulting diffusion coefficient estimates are an increasing function of temperature, whose detailed functional form depends on the degree of static disorder. With a realistic static disorder parameter (σs ≃ 0.06 eV), the diffusion coefficients decrease from D ∼ 1 × 10-2 cm2 s-1 to D ∼ 1 × 10-3 cm2 s-1, in qualitative agreement with experimental data for P3HT. The dynamical scenario obtained from our simulations shows that exciton migration in P3HT-type chains is a largely adiabatic process throughout the temperature regime we investigated (i.e., T = 50-300 K). The resulting picture of exciton migration is a coherent, but not bandlike, motion of an exciton-polaron driven by fluctuations induced by low-frequency modes. This process acquires partial hopping character if static disorder becomes prominent and Anderson localization sets in.
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Affiliation(s)
- Rainer Hegger
- Institute for Physical and Theoretical Chemistry, Goethe University, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
| | - Robert Binder
- Institute for Physical and Theoretical Chemistry, Goethe University, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
| | - Irene Burghardt
- Institute for Physical and Theoretical Chemistry, Goethe University, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
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Dostál J, Alster J. Interplay between coherence-time undersampling and scattered light in two-dimensional electronic spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:093103. [PMID: 33003825 DOI: 10.1063/5.0009513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 08/12/2020] [Indexed: 06/11/2023]
Abstract
Scanning pulse delays in multi-pulse non-linear optical spectroscopy experiments is a major contributor to lengthy data acquisition. Using large steps for the scan can significantly speed up the experiment. However, an improper choice of step length can cause distortions to the resulting spectra, especially if the light scattered on the sample is mixed into the signal. In this work, we identify potential sources of such distortions and suggest appropriate countermeasures to avoid them while maintaining a faster data collection.
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Affiliation(s)
- Jakub Dostál
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, 121 16 Prague, Czech Republic
| | - Jan Alster
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, 121 16 Prague, Czech Republic
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30
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Pandya R, Chen RYS, Gu Q, Gorman J, Auras F, Sung J, Friend R, Kukura P, Schnedermann C, Rao A. Femtosecond Transient Absorption Microscopy of Singlet Exciton Motion in Side-Chain Engineered Perylene-Diimide Thin Films. J Phys Chem A 2020; 124:2721-2730. [PMID: 32130861 PMCID: PMC7132576 DOI: 10.1021/acs.jpca.0c00346] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/04/2020] [Indexed: 12/21/2022]
Abstract
We present a statistical analysis of femtosecond transient absorption microscopy applied to four different organic semiconductor thin films based on perylene-diimide (PDI). By achieving a temporal resolution of 12 fs with simultaneous sub-10 nm spatial precision, we directly probe the underlying exciton transport characteristics within 3 ps after photoexcitation free of model assumptions. Our study reveals sub-picosecond coherent exciton transport (12-45 cm2 s-1) followed by a diffusive phase of exciton transport (3-17 cm2 s-1). A comparison between the different films suggests that the exciton transport in the studied materials is intricately linked to their nanoscale morphology, with PDI films that form large crystalline domains exhibiting the largest diffusion coefficients and transport lengths. Our study demonstrates the advantages of directly studying ultrafast transport properties at the nanometer length scale and highlights the need to examine nanoscale morphology when investigating exciton transport in organic as well as inorganic semiconductors.
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Affiliation(s)
- Raj Pandya
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Richard Y. S. Chen
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Qifei Gu
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Jeffrey Gorman
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Florian Auras
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Jooyoung Sung
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Richard Friend
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Philipp Kukura
- Physical
and Theoretical Chemistry Laboratory, Oxford
University, South Parks Road, Oxford OX1 3QZ, U.K.
| | - Christoph Schnedermann
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
| | - Akshay Rao
- Department
of Physics, Cavendish Laboratory, University
of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
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31
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Malý P, Lüttig J, Mueller S, Schreck MH, Lambert C, Brixner T. Coherently and fluorescence-detected two-dimensional electronic spectroscopy: direct comparison on squaraine dimers. Phys Chem Chem Phys 2020; 22:21222-21237. [PMID: 32930273 DOI: 10.1039/d0cp03218b] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Optical two-dimensional electronic spectroscopy (2DES) is now widely utilized to study excitonic structure and dynamics of a broad range of systems, from molecules to solid state. Besides the traditional experimental implementation using phase matching and coherent signal field detection, action-based approaches that detect incoherent signals such as fluorescence have been gaining popularity in recent years. While incoherent detection extends the range of applicability of 2DES, the observed spectra are not equivalent to the coherently detected ones. This raises questions about their interpretation and the sensitivity of the technique. Here we directly compare, both experimentally and theoretically, four-wave mixing coherently and fluorescence-detected 2DES of a series of squaraine dimers of increasing electronic coupling. All experiments are qualitatively well reproduced by a Frenkel exciton model with secular Redfield theory description of excitation dynamics. We contrast the spectral features and the sensitivities of both techniques with respect to exciton energies, delocalization, coherent and dissipative dynamics, and exciton-exciton annihilation. Discussing the fundamental and practical differences, we demonstrate the degree of complementarity of the techniques.
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Affiliation(s)
- Pavel Malý
- Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany.
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