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Ghosh P, Alvertis AM, Chowdhury R, Murto P, Gillett AJ, Dong S, Sneyd AJ, Cho HH, Evans EW, Monserrat B, Li F, Schnedermann C, Bronstein H, Friend RH, Rao A. Decoupling excitons from high-frequency vibrations in organic molecules. Nature 2024; 629:355-362. [PMID: 38720042 PMCID: PMC11078737 DOI: 10.1038/s41586-024-07246-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 02/27/2024] [Indexed: 05/12/2024]
Abstract
The coupling of excitons in π-conjugated molecules to high-frequency vibrational modes, particularly carbon-carbon stretch modes (1,000-1,600 cm-1) has been thought to be unavoidable1,2. These high-frequency modes accelerate non-radiative losses and limit the performance of light-emitting diodes, fluorescent biomarkers and photovoltaic devices. Here, by combining broadband impulsive vibrational spectroscopy, first-principles modelling and synthetic chemistry, we explore exciton-vibration coupling in a range of π-conjugated molecules. We uncover two design rules that decouple excitons from high-frequency vibrations. First, when the exciton wavefunction has a substantial charge-transfer character with spatially disjoint electron and hole densities, we find that high-frequency modes can be localized to either the donor or acceptor moiety, so that they do not significantly perturb the exciton energy or its spatial distribution. Second, it is possible to select materials such that the participating molecular orbitals have a symmetry-imposed non-bonding character and are, thus, decoupled from the high-frequency vibrational modes that modulate the π-bond order. We exemplify both these design rules by creating a series of spin radical systems that have very efficient near-infrared emission (680-800 nm) from charge-transfer excitons. We show that these systems have substantial coupling to vibrational modes only below 250 cm-1, frequencies that are too low to allow fast non-radiative decay. This enables non-radiative decay rates to be suppressed by nearly two orders of magnitude in comparison to π-conjugated molecules with similar bandgaps. Our results show that losses due to coupling to high-frequency modes need not be a fundamental property of these systems.
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Affiliation(s)
- Pratyush Ghosh
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Antonios M Alvertis
- KBR, Inc., NASA Ames Research Center, Moffett Field, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | | | - Petri Murto
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | - Shengzhi Dong
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | | | - Hwan-Hee Cho
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Department of Chemistry, Swansea University, Swansea, UK
| | - Bartomeu Monserrat
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | | | - Hugo Bronstein
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
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2
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Hudson JM, Evans EW. Radical Spin Polarization and Magnetosensitivity from Reversible Energy Transfer. J Phys Chem Lett 2024; 15:4130-4135. [PMID: 38593182 PMCID: PMC11033935 DOI: 10.1021/acs.jpclett.4c00656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 03/27/2024] [Accepted: 03/29/2024] [Indexed: 04/11/2024]
Abstract
Molecular spins provide potential building units for future quantum information science and spintronic technologies. In particular, doublet (S = 1/2) and triplet (S = 1) molecular spin states have the potential for excellent optical and spin properties for these applications if useful photon-spin mechanisms at room temperature can be devised. Here we explore the potential of exploiting reversible energy transfer between triplet and doublet states to establish magnetosensitive luminescence and spin polarization. We investigate the dependence of the photon-spin mechanism on the magnitude and sign of the exchange interaction between the doublet and triplet spin components in amorphous and crystalline model systems. The design of a magnetic field inclination sensor is proposed from understanding the required "structure" (spin interactions) to "function" (magnetosensitivity).
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Affiliation(s)
- John M. Hudson
- Department
of Chemistry, Swansea University, Swansea SA2 8PP, United Kingdom
- Centre
for Integrative Semiconductor Materials, Swansea SA1 8EN, United Kingdom
| | - Emrys W. Evans
- Department
of Chemistry, Swansea University, Swansea SA2 8PP, United Kingdom
- Centre
for Integrative Semiconductor Materials, Swansea SA1 8EN, United Kingdom
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3
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Cho HH, Gorgon S, Hung HC, Huang JY, Wu YR, Li F, Greenham NC, Evans EW, Friend RH. Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off. Adv Mater 2023; 35:e2303666. [PMID: 37684741 DOI: 10.1002/adma.202303666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 08/08/2023] [Indexed: 09/10/2023]
Abstract
Organic radicals have been of interest due to their potential to replace nonradical-based organic emitters, especially for deep-red/near-infrared (NIR) electroluminescence (EL), based on the spin-allowed doublet fluorescence. However, the performance of the radical-based EL devices is limited by low carrier mobility which causes a large efficiency roll-off at high current densities. Here, highly efficient and bright doublet EL devices are reported by combining a thermally activated delayed fluorescence (TADF) host that supports both electron and hole transport and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. Steady-state and transient photophysical studies reveal the optical signatures of doublet luminescence mechanisms arising from both host and guest photoexcitation. The host system presented here allows balanced hole and electron currents, and a high maximum external quantum efficiency (EQE) of 17.4% at 707 nm peak emission with substantially improved efficiency roll-off is reported: over 70% of the maximum EQE (12.2%) is recorded at 10 mA cm-2 , and even at 100 mA cm-2 , nearly 50% of the maximum EQE (8.4%) is maintained. This is an important step in the practical application of organic radicals to NIR light-emitting devices.
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Affiliation(s)
- Hwan-Hee Cho
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Sebastian Gorgon
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Hsiao-Chun Hung
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Jun-Yu Huang
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Yuh-Renn Wu
- Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, 10617, Taipei, Taiwan
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Qianjin Avenue 2699, Changchun, 130012, P. R. China
| | - Neil C Greenham
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Emrys W Evans
- Department of Chemistry, Swansea University, Singleton Park, Swansea, SA2 8PP, UK
| | - Richard H Friend
- Cavendish Laboratory, Department of Physics, University of Cambridge, J J Thomson Avenue, Cambridge, CB3 0HE, UK
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4
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Gorgon S, Lv K, Grüne J, Drummond BH, Myers WK, Londi G, Ricci G, Valverde D, Tonnelé C, Murto P, Romanov AS, Casanova D, Dyakonov V, Sperlich A, Beljonne D, Olivier Y, Li F, Friend RH, Evans EW. Reversible spin-optical interface in luminescent organic radicals. Nature 2023; 620:538-544. [PMID: 37587296 PMCID: PMC10432275 DOI: 10.1038/s41586-023-06222-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 05/16/2023] [Indexed: 08/18/2023]
Abstract
Molecules present a versatile platform for quantum information science1,2 and are candidates for sensing and computation applications3,4. Robust spin-optical interfaces are key to harnessing the quantum resources of materials5. To date, carbon-based candidates have been non-luminescent6,7, which prevents optical readout via emission. Here we report organic molecules showing both efficient luminescence and near-unity generation yield of excited states with spin multiplicity S > 1. This was achieved by designing an energy resonance between emissive doublet and triplet levels, here on covalently coupled tris(2,4,6-trichlorophenyl) methyl-carbazole radicals and anthracene. We observed that the doublet photoexcitation delocalized onto the linked acene within a few picoseconds and subsequently evolved to a pure high-spin state (quartet for monoradical, quintet for biradical) of mixed radical-triplet character near 1.8 eV. These high-spin states are coherently addressable with microwaves even at 295 K, with optical readout enabled by reverse intersystem crossing to emissive states. Furthermore, for the biradical, on return to the ground state the previously uncorrelated radical spins either side of the anthracene shows strong spin correlation. Our approach simultaneously supports a high efficiency of initialization, spin manipulations and light-based readout at room temperature. The integration of luminescence and high-spin states creates an organic materials platform for emerging quantum technologies.
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Affiliation(s)
- Sebastian Gorgon
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK.
| | - Kuo Lv
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | - Jeannine Grüne
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - William K Myers
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Giacomo Londi
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Gaetano Ricci
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Danillo Valverde
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | | | - Petri Murto
- Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | | | - Vladimir Dyakonov
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
| | - Andreas Sperlich
- Experimental Physics VI, Faculty of Physics and Astronomy, University of Würzburg, Würzburg, Germany
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, University of Mons, Mons, Belgium
| | - Yoann Olivier
- Laboratory for Computational Modelling of Functional Materials, Namur Institute of Structured Matter, University of Namur, Namur, Belgium
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | | | - Emrys W Evans
- Department of Chemistry, Swansea University, Swansea, UK.
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5
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Gillett AJ, Pershin A, Pandya R, Feldmann S, Sneyd AJ, Alvertis AM, Evans EW, Thomas TH, Cui LS, Drummond BH, Scholes GD, Olivier Y, Rao A, Friend RH, Beljonne D. Dielectric control of reverse intersystem crossing in thermally activated delayed fluorescence emitters. Nat Mater 2022; 21:1150-1157. [PMID: 35927434 PMCID: PMC7613666 DOI: 10.1038/s41563-022-01321-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 06/13/2022] [Indexed: 05/22/2023]
Abstract
Thermally activated delayed fluorescence enables organic semiconductors with charge transfer-type excitons to convert dark triplet states into bright singlets via reverse intersystem crossing. However, thus far, the contribution from the dielectric environment has received insufficient attention. Here we study the role of the dielectric environment in a range of thermally activated delayed fluorescence materials with varying changes in dipole moment upon optical excitation. In dipolar emitters, we observe how environmental reorganization after excitation triggers the full charge transfer exciton formation, minimizing the singlet-triplet energy gap, with the emergence of two (reactant-inactive) modes acting as a vibrational fingerprint of the charge transfer product. In contrast, the dielectric environment plays a smaller role in less dipolar materials. The analysis of energy-time trajectories and their free-energy functions reveals that the dielectric environment substantially reduces the activation energy for reverse intersystem crossing in dipolar thermally activated delayed fluorescence emitters, increasing the reverse intersystem crossing rate by three orders of magnitude versus the isolated molecule.
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Affiliation(s)
| | - Anton Pershin
- Laboratory for Chemistry of Novel Materials, Université de Mons, Mons, Belgium
- Wigner Research Centre for Physics, Budapest, Hungary
| | - Raj Pandya
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Sascha Feldmann
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | | | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
- Department of Chemistry, Swansea University, Swansea, UK
| | - Tudor H Thomas
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Lin-Song Cui
- CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, China
| | | | | | - Yoann Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, Namur, Belgium
| | - Akshay Rao
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - David Beljonne
- Laboratory for Chemistry of Novel Materials, Université de Mons, Mons, Belgium.
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6
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Gillett AJ, Tonnelé C, Londi G, Ricci G, Catherin M, Unson DML, Casanova D, Castet F, Olivier Y, Chen WM, Zaborova E, Evans EW, Drummond BH, Conaghan PJ, Cui LS, Greenham NC, Puttisong Y, Fages F, Beljonne D, Friend RH. Spontaneous exciton dissociation enables spin state interconversion in delayed fluorescence organic semiconductors. Nat Commun 2021; 12:6640. [PMID: 34789719 PMCID: PMC8599618 DOI: 10.1038/s41467-021-26689-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 10/14/2021] [Indexed: 11/09/2022] Open
Abstract
Engineering a low singlet-triplet energy gap (ΔEST) is necessary for efficient reverse intersystem crossing (rISC) in delayed fluorescence (DF) organic semiconductors but results in a small radiative rate that limits performance in LEDs. Here, we study a model DF material, BF2, that exhibits a strong optical absorption (absorption coefficient = 3.8 × 105 cm-1) and a relatively large ΔEST of 0.2 eV. In isolated BF2 molecules, intramolecular rISC is slow (delayed lifetime = 260 μs), but in aggregated films, BF2 generates intermolecular charge transfer (inter-CT) states on picosecond timescales. In contrast to the microsecond intramolecular rISC that is promoted by spin-orbit interactions in most isolated DF molecules, photoluminescence-detected magnetic resonance shows that these inter-CT states undergo rISC mediated by hyperfine interactions on a ~24 ns timescale and have an average electron-hole separation of ≥1.5 nm. Transfer back to the emissive singlet exciton then enables efficient DF and LED operation. Thus, access to these inter-CT states, which is possible even at low BF2 doping concentrations of 4 wt%, resolves the conflicting requirements of fast radiative emission and low ΔEST in organic DF emitters.
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Affiliation(s)
- Alexander J Gillett
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK.
| | - Claire Tonnelé
- Donostia International Physics Centre (DIPC), Donostia, Euskadi, Spain
| | - Giacomo Londi
- Laboratory for Chemistry of Novel Materials, Université de Mons, Place du Parc 20, 7000, Mons, Belgium
| | - Gaetano Ricci
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, B-5000, Namur, Belgium
| | - Manon Catherin
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France
| | - Darcy M L Unson
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - David Casanova
- Donostia International Physics Centre (DIPC), Donostia, Euskadi, Spain
| | - Frédéric Castet
- Institut des Sciences Moléculaires, Université de Bordeaux, 33405, Talence, France
| | - Yoann Olivier
- Unité de Chimie Physique Théorique et Structurale & Laboratoire de Physique du Solide, Namur Institute of Structured Matter, Université de Namur, B-5000, Namur, Belgium
| | - Weimin M Chen
- Department of Physics, Chemistry and Biology (IFM) Linköping University, Linköping, Sweden
| | - Elena Zaborova
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- Department of Chemistry, Swansea University, Singleton Park, Swansea, UK
| | - Bluebell H Drummond
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - Patrick J Conaghan
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- ARC Centre of Excellence in Exciton Science, School of Chemistry, University of Sydney, Sydney, NSW, 2006, Australia
| | - Lin-Song Cui
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
- Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK
| | - Yuttapoom Puttisong
- Department of Physics, Chemistry and Biology (IFM) Linköping University, Linköping, Sweden.
| | - Frédéric Fages
- Aix Marseille Univ, CNRS, CINaM UMR 7325, AMUtech, Campus de Luminy, 13288, Marseille, France.
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials, Université de Mons, Place du Parc 20, 7000, Mons, Belgium.
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, UK.
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7
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Drummond BH, Aizawa N, Zhang Y, Myers WK, Xiong Y, Cooper MW, Barlow S, Gu Q, Weiss LR, Gillett AJ, Credgington D, Pu YJ, Marder SR, Evans EW. Electron spin resonance resolves intermediate triplet states in delayed fluorescence. Nat Commun 2021; 12:4532. [PMID: 34312394 PMCID: PMC8313702 DOI: 10.1038/s41467-021-24612-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 06/22/2021] [Indexed: 11/09/2022] Open
Abstract
Molecular organic fluorophores are currently used in organic light-emitting diodes, though non-emissive triplet excitons generated in devices incorporating conventional fluorophores limit the efficiency. This limit can be overcome in materials that have intramolecular charge-transfer excitonic states and associated small singlet-triplet energy separations; triplets can then be converted to emissive singlet excitons resulting in efficient delayed fluorescence. However, the mechanistic details of the spin interconversion have not yet been fully resolved. We report transient electron spin resonance studies that allow direct probing of the spin conversion in a series of delayed fluorescence fluorophores with varying energy gaps between local excitation and charge-transfer triplet states. The observation of distinct triplet signals, unusual in transient electron spin resonance, suggests that multiple triplet states mediate the photophysics for efficient light emission in delayed fluorescence emitters. We reveal that as the energy separation between local excitation and charge-transfer triplet states decreases, spin interconversion changes from a direct, singlet-triplet mechanism to an indirect mechanism involving intermediate states.
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Affiliation(s)
- Bluebell H Drummond
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
- Centre for Advanced Electron Spin Resonance (CAESR), Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Naoya Aizawa
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, Japan
| | - Yadong Zhang
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - William K Myers
- Centre for Advanced Electron Spin Resonance (CAESR), Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford, UK
| | - Yao Xiong
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Matthew W Cooper
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Stephen Barlow
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Qinying Gu
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Leah R Weiss
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA
| | - Alexander J Gillett
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Dan Credgington
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK
| | - Yong-Jin Pu
- RIKEN Center for Emergent Matter Science (CEMS), Saitama, Japan
| | - Seth R Marder
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Emrys W Evans
- Department of Physics, Cavendish Laboratory, J J Thomson Avenue, University of Cambridge, Cambridge, UK.
- Department of Chemistry, Swansea University, Swansea, UK.
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8
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Greenfield JL, Di Nuzzo D, Evans EW, Senanayak SP, Schott S, Deacon JT, Peugeot A, Myers WK, Sirringhaus H, Friend RH, Nitschke JR. Electrically Induced Mixed Valence Increases the Conductivity of Copper Helical Metallopolymers. Adv Mater 2021; 33:e2100403. [PMID: 33955595 DOI: 10.1002/adma.202100403] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 03/11/2021] [Indexed: 06/12/2023]
Abstract
Controlling the flow of electrical current at the nanoscale typically requires complex top-down approaches. Here, a bottom-up approach is employed to demonstrate resistive switching within molecular wires that consist of double-helical metallopolymers and are constructed by self-assembly. When the material is exposed to an electric field, it is determined that ≈25% of the copper atoms oxidize from CuI to CuII , without rupture of the polymer chain. The ability to sustain such a high level of oxidation is unprecedented in a copper-based molecule: it is made possible here by the double helix compressing in order to satisfy the new coordination geometry required by CuII . This mixed-valence structure exhibits a 104 -fold increase in conductivity, which is projected to last on the order of years. The increase in conductivity is explained as being promoted by the creation, upon oxidation, of partly filled d z 2 orbitals aligned along the mixed-valence copper array; the long-lasting nature of the change in conductivity is due to the structural rearrangement of the double-helix, which poses an energetic barrier to re-reduction. This work establishes helical metallopolymers as a new platform for controlling currents at the nanoscale.
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Affiliation(s)
- Jake L Greenfield
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Daniele Di Nuzzo
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | | | - Sam Schott
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Jason T Deacon
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Adele Peugeot
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - William K Myers
- Centre for Advanced ESR, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, UK
| | - Henning Sirringhaus
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
| | - Jonathan R Nitschke
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
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9
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Abdurahman A, Hele TJH, Gu Q, Zhang J, Peng Q, Zhang M, Friend RH, Li F, Evans EW. Understanding the luminescent nature of organic radicals for efficient doublet emitters and pure-red light-emitting diodes. Nat Mater 2020; 19:1224-1229. [PMID: 32541936 DOI: 10.1038/s41563-020-0705-9] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 05/11/2020] [Indexed: 06/11/2023]
Abstract
The doublet-spin nature of radical emitters is advantageous for applications in organic light-emitting diodes, as it avoids the formation of triplet excitons that limit the electroluminescence efficiency of non-radical emitters. However, radicals generally show low optical absorption and photoluminescence yields. Here we explain the poor optical properties of radicals based on alternant hydrocarbons, and establish design rules to increase the absorption and luminescence yields for donor-acceptor-type radicals. We show that non-alternant systems are necessary to lift the degeneracy of the lowest energy orbital excitations; moreover, intensity borrowing from an intense high-lying transition by the low-energy charge-transfer excitation enhances the oscillator strength of the emitter. We apply these rules to design tris(2,4,6-trichlorophenyl)methyl-pyridoindolyl derivatives with a high photoluminescence quantum yield (>90%). Organic light-emitting diodes based on these molecules showed a pure-red emission with an over 12% external quantum efficiency. These insights may be beneficial for the rational design and discovery of highly luminescent doublet emitters.
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Affiliation(s)
- Alim Abdurahman
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | | | - Qinying Gu
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Jiangbin Zhang
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Qiming Peng
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
- Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, P. R. China
| | - Ming Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China
| | | | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, P. R. China.
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
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10
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Ascherl L, Evans EW, Gorman J, Orsborne S, Bessinger D, Bein T, Friend RH, Auras F. Perylene-Based Covalent Organic Frameworks for Acid Vapor Sensing. J Am Chem Soc 2019; 141:15693-15699. [DOI: 10.1021/jacs.9b08079] [Citation(s) in RCA: 132] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Laura Ascherl
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Emrys W. Evans
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Jeffrey Gorman
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Sarah Orsborne
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Derya Bessinger
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Thomas Bein
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377 Munich, Germany
| | - Richard H. Friend
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Florian Auras
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
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11
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Guo H, Peng Q, Chen XK, Gu Q, Dong S, Evans EW, Gillett AJ, Ai X, Zhang M, Credgington D, Coropceanu V, Friend RH, Brédas JL, Li F. High stability and luminescence efficiency in donor-acceptor neutral radicals not following the Aufbau principle. Nat Mater 2019; 18:977-984. [PMID: 31332338 DOI: 10.1038/s41563-019-0433-1] [Citation(s) in RCA: 107] [Impact Index Per Article: 21.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 06/13/2019] [Indexed: 06/10/2023]
Abstract
With their unusual electronic structures, organic radical molecules display luminescence properties potentially relevant to lighting applications; yet, their luminescence quantum yield and stability lag behind those of other organic emitters. Here, we designed donor-acceptor neutral radicals based on an electron-poor perchlorotriphenylmethyl or tris(2,4,6-trichlorophenyl)methyl radical moiety combined with different electron-rich groups. Experimental and quantum-chemical studies demonstrate that the molecules do not follow the Aufbau principle: the singly occupied molecular orbital is found to lie below the highest (doubly) occupied molecular orbital. These donor-acceptor radicals have a strong emission yield (up to 54%) and high photostability, with estimated half-lives reaching up to several months under pulsed ultraviolet laser irradiation. Organic light-emitting diodes based on such a radical emitter show deep-red/near-infrared emission with a maximal external quantum efficiency of 5.3%. Our results provide a simple molecular-design strategy for stable, highly luminescent radicals with non-Aufbau electronic structures.
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Affiliation(s)
- Haoqing Guo
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Qiming Peng
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
- Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing, China
| | - Xian-Kai Chen
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | - Qinying Gu
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Shengzhi Dong
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | | | - Xin Ai
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Ming Zhang
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China
| | - Dan Credgington
- Cavendish Laboratory, University of Cambridge, Cambridge, UK
| | - Veaceslav Coropceanu
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA
| | | | - Jean-Luc Brédas
- School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Feng Li
- State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, China.
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
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12
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Montanaro S, Gillett AJ, Feldmann S, Evans EW, Plasser F, Friend RH, Wright IA. Red-shifted delayed fluorescence at the expense of photoluminescence quantum efficiency - an intramolecular charge-transfer molecule based on a benzodithiophene-4,8-dione acceptor. Phys Chem Chem Phys 2019; 21:10580-10586. [PMID: 31074469 DOI: 10.1039/c9cp02186h] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Employing the thiophene based quinone, benzo[1,2-b:4,5-b']dithiophene-4,8-dione, as the electron-accepting moiety alongside N-phenylcarbazole donors to produce a donor-π-acceptor-π-donor (D-π-A-π-D) molecule has yielded a new red emitter displaying delayed fluorescence. This new molecule shows strongly (over 100 nm) red-shifted emission when compared to an anthraquinone based analogue. Cyclic voltammetry complemented by computational insights prove that this red-shift is due to the significantly stronger electron-accepting ability of the thiophene quinone compared to anthraquinone. Photophysical and computational studies of this molecule have revealed that while the presence of the thiophene containing acceptor facilitates rapid intersystem crossing which is comparable to anthraquinone analogues, the reverse intersystem crossing rate is slow and non-radiative decay is rapid which we can attribute to low-lying locally excited states. This limits the total photoluminescence quantum efficiency to less than 10% in both solution and the solid state. These results provide a useful example of how very minor structural variations can have a defining impact on the photophysical properties of new molecular materials.
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Affiliation(s)
- Stephanie Montanaro
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
| | - Alexander J Gillett
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Sascha Feldmann
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Emrys W Evans
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Felix Plasser
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
| | - Richard H Friend
- Optoelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Iain A Wright
- Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
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13
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Ascherl L, Evans EW, Hennemann M, Di Nuzzo D, Hufnagel AG, Beetz M, Friend RH, Clark T, Bein T, Auras F. Solvatochromic covalent organic frameworks. Nat Commun 2018; 9:3802. [PMID: 30228278 PMCID: PMC6143592 DOI: 10.1038/s41467-018-06161-w] [Citation(s) in RCA: 114] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 08/16/2018] [Indexed: 11/09/2022] Open
Abstract
Covalent organic frameworks (COFs) are an emerging class of highly tuneable crystalline, porous materials. Here we report the first COFs that change their electronic structure reversibly depending on the surrounding atmosphere. These COFs can act as solid-state supramolecular solvatochromic sensors that show a strong colour change when exposed to humidity or solvent vapours, dependent on vapour concentration and solvent polarity. The excellent accessibility of the pores in vertically oriented films results in ultrafast response times below 200 ms, outperforming commercially available humidity sensors by more than an order of magnitude. Employing a solvatochromic COF film as a vapour-sensitive light filter, we demonstrate a fast humidity sensor with full reversibility and stability over at least 4000 cycles. Considering their immense chemical diversity and modular design, COFs with fine-tuned solvatochromic properties could broaden the range of possible applications for these materials in sensing and optoelectronics.
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Affiliation(s)
- Laura Ascherl
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377, Munich, Germany
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Matthias Hennemann
- Computer-Chemie-Centrum, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Nägelsbachstraße 25, 91052, Erlangen, Germany
| | - Daniele Di Nuzzo
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Alexander G Hufnagel
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377, Munich, Germany
| | - Michael Beetz
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377, Munich, Germany
| | - Richard H Friend
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Timothy Clark
- Computer-Chemie-Centrum, Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Nägelsbachstraße 25, 91052, Erlangen, Germany
| | - Thomas Bein
- Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstraße 5-13, 81377, Munich, Germany.
| | - Florian Auras
- Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
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14
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Greenfield JL, Evans EW, Di Nuzzo D, Di Antonio M, Friend RH, Nitschke JR. Unraveling Mechanisms of Chiral Induction in Double-Helical Metallopolymers. J Am Chem Soc 2018; 140:10344-10353. [PMID: 30024156 PMCID: PMC6114842 DOI: 10.1021/jacs.8b06195] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Indexed: 12/18/2022]
Abstract
Self-assembled helical polymers hold great promise as new functional materials, where helical handedness controls useful properties such as circularly polarized light emission or electron spin. The technique of subcomponent self-assembly can generate helical polymers from readily prepared monomers. Here we present three distinct strategies for chiral induction in double-helical metallopolymers prepared via subcomponent self-assembly: (1) employing an enantiopure monomer, (2) polymerization in a chiral solvent, (3) using an enantiopure initiating group. Kinetic and thermodynamic models were developed to describe the polymer growth mechanisms and quantify the strength of chiral induction, respectively. We found the degree of chiral induction to vary as a function of polymer length. Ordered, rod-like aggregates more than 70 nm long were also observed in the solid state. Our findings provide a basis to choose the most suitable method of chiral induction based on length, regiochemical, and stereochemical requirements, allowing stereochemical control to be established in easily accessible ways.
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Affiliation(s)
- Jake L. Greenfield
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United
Kingdom
| | - Emrys W. Evans
- Cavendish
Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Daniele Di Nuzzo
- Cavendish
Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Marco Di Antonio
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United
Kingdom
| | - Richard H. Friend
- Cavendish
Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Jonathan R. Nitschke
- Department
of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United
Kingdom
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15
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Conaghan PJ, Menke SM, Romanov AS, Jones STE, Pearson AJ, Evans EW, Bochmann M, Greenham NC, Credgington D. Efficient Vacuum-Processed Light-Emitting Diodes Based on Carbene-Metal-Amides. Adv Mater 2018; 30:e1802285. [PMID: 29984854 DOI: 10.1002/adma.201802285] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/26/2018] [Indexed: 06/08/2023]
Abstract
Efficient vacuum-processed organic light-emitting diodes are fabricated using a carbene-metal-amide material, CMA1. An electroluminescence (EL) external quantum efficiency of 23% is achieved in a host-free emissive layer comprising pure CMA1. Furthermore external quantum efficiencies of up to 26.9% are achieved in host-guest emissive layers. EL spectra are found to depend on both the emissive-layer doping concentration and the choice of host material, enabling tuning of emission color from mid-green (Commission Internationale de l'Éclairage co-ordinates [0.24, 0.46]) to sky blue ([0.22 0.35]) without changing dopant. This tuning is achieved without compromising luminescence efficiency (>80%) while maintaining a short radiative lifetime of triplets (<1 μs).
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Affiliation(s)
- Patrick J Conaghan
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - S Matthew Menke
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Alexander S Romanov
- School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK
| | - Saul T E Jones
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Andrew J Pearson
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Emrys W Evans
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Manfred Bochmann
- School of Chemistry, University of East Anglia, Earlham Road, Norwich, NR4 7TJ, UK
| | - Neil C Greenham
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
| | - Dan Credgington
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK
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16
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Evans EW, Olivier Y, Puttisong Y, Myers WK, Hele TJH, Menke SM, Thomas TH, Credgington D, Beljonne D, Friend RH, Greenham NC. Vibrationally Assisted Intersystem Crossing in Benchmark Thermally Activated Delayed Fluorescence Molecules. J Phys Chem Lett 2018; 9:4053-4058. [PMID: 29957961 DOI: 10.1021/acs.jpclett.8b01556] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Electrically injected charge carriers in organic light-emitting devices (OLEDs) undergo recombination events to form singlet and triplet states in a 1:3 ratio, representing a fundamental hurdle for achieving high quantum efficiency. Dopants based on thermally activated delayed fluorescence (TADF) have emerged as promising candidates for addressing the spin statistics issue in OLEDs. In these materials, reverse singlet-triplet intersystem crossing (rISC) becomes efficient, thereby activating luminescence pathways for weakly emissive triplet states. However, despite a growing consensus that torsional vibrations facilitate spin-orbit-coupling- (SOC-) driven ISC in these molecules, there is a shortage of experimental evidence. We use transient electron spin resonance and theory to show unambiguously that SOC interactions drive spin conversion and that ISC is a dynamic process gated by conformational fluctuations for benchmark carbazolyl-dicyanobenzene TADF emitters.
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Affiliation(s)
- Emrys W Evans
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - Yoann Olivier
- Laboratory for Chemistry of Novel Materials , University of Mons , Place du Parc 20 , B-7000 Mons , Belgium
| | - Yuttapoom Puttisong
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - William K Myers
- Centre for Advanced Electron Spin Resonance (CAESR) , University of Oxford , South Parks Road , Oxford OX1 3QR , United Kingdom
| | - Timothy J H Hele
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - S Matthew Menke
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - Tudor H Thomas
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - Dan Credgington
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - David Beljonne
- Laboratory for Chemistry of Novel Materials , University of Mons , Place du Parc 20 , B-7000 Mons , Belgium
| | - Richard H Friend
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
| | - Neil C Greenham
- Cavendish Laboratory , University of Cambridge , J. J. Thomson Avenue , Cambridge CB3 0HE , United Kingdom
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17
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Evans EW, Redmond EC. An assessment of food safety information provision for UK chemotherapy patients to reduce the risk of foodborne infection. Public Health 2017; 153:25-35. [PMID: 28822850 DOI: 10.1016/j.puhe.2017.06.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 06/12/2017] [Accepted: 06/19/2017] [Indexed: 11/17/2022]
Abstract
OBJECTIVES Given the increased risk of foodborne infection to cancer patients receiving chemotherapy treatment, and the risk of listeriosis reportedly five-times greater to this immunocompromised patient group, there is a need to ensure the implementation of domestic food safety practices among chemotherapy patients and their family caregivers. However, information regarding the adequacy of resources to inform and enable patients to implement domestic food safety practices to reduce the risk of foodborne infection is limited. Consequently, this study aimed to evaluate the provision of food safety information available to UK chemotherapy patients. STUDY DESIGN In-depth semi-structured interviews and content analysis of online patient information resources. METHODS Interviews with patients and family caregivers (n = 15) were conducted to explore food-related experiences during chemotherapy treatment. Online food-related information resources for chemotherapy patients (n = 45) were obtained from 35 of 154 National Health Service chemotherapy providers in England, Scotland, and Wales, the Department of Health (DoH) and three of 184 identified UK cancer charities. Identified food-related information resources were reviewed using a content-analysis approach to assess the inclusion of food safety information for chemotherapy patients. RESULTS In-depth interviews established that many patients indicated awareness of immunosuppression during treatment. Although patients reported practicing caution to reduce the risk of communicable diseases by avoiding crowded spaces/public transport, food safety was reported to be of minimal concern during treatment and the risk of foodborne infection was often underestimated. The review of online food-related patient information resources established that many resources failed to highlight the increased risk of foodborne infection and emphasize the importance of food safety for patients during chemotherapy treatment. Considerable information gaps exist, particularly in relation to listeriosis prevention practices. Cumulatively, information was inconsistent, insufficient, and varied between resources. CONCLUSION The study has identified the need for an effective, standardized food safety resource specifically targeting chemotherapy patients and family caregivers. Such intervention is essential to assist efforts in reducing the risks associated with foodborne infection among chemotherapy patients.
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Affiliation(s)
- E W Evans
- ZERO2FIVE Food Industry Centre, Cardiff Metropolitan University, United Kingdom.
| | - E C Redmond
- ZERO2FIVE Food Industry Centre, Cardiff Metropolitan University, United Kingdom
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18
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Evans EW, Kattnig DR, Henbest KB, Hore PJ, Mackenzie SR, Timmel CR. Sub-millitesla magnetic field effects on the recombination reaction of flavin and ascorbic acid radicals. J Chem Phys 2016; 145:085101. [DOI: 10.1063/1.4961266] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Emrys W. Evans
- Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford, United Kingdom
| | - Daniel R. Kattnig
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Kevin B. Henbest
- Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford, United Kingdom
| | - P. J. Hore
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Stuart R. Mackenzie
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Christiane R. Timmel
- Department of Chemistry, Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford, United Kingdom
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19
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Evans EW, Li J, Storey JG, Maeda K, Henbest KB, Dodson CA, Hore PJ, Mackenzie SR, Timmel CR. Sensitive fluorescence-based detection of magnetic field effects in photoreactions of flavins. Phys Chem Chem Phys 2016; 17:18456-63. [PMID: 26108474 DOI: 10.1039/c5cp00723b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic field effect studies have been conducted on a variety of flavin-based radical pair systems chosen to model the magnetosensitivity of the photoinduced radical pairs found in cryptochrome flavoproteins. Cryptochromes are blue-light photoreceptor proteins which are thought to mediate avian magnetoreception, an hypothesis supported by recent in vitro observations of magnetic field-dependent reaction kinetics for a light-induced radical pair in a cryptochrome from the plant Arabidopsis thaliana. Many cryptochromes are difficult to express in large quantities or high concentrations and are easily photodegraded. Magnetic field effects are typically measured by spectroscopic detection of the transient radical (pair) concentrations. Due to its low sensitivity, single-pass transient absorption spectroscopy can be of limited use in such experiments and much recent work has involved development of other methodologies offering improved sensitivity. Here we explore the use of flavin fluorescence as the magnetosensitive probe and demonstrate the exceptional sensitivity of this technique which allows the detection of magnetic field effects in flavin samples at sub-nanomolar concentrations and in cryptochromes.
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Affiliation(s)
- Emrys W Evans
- Department of Chemistry, University of Oxford, Centre for Advanced Electron Spin Resonance, Oxford, OX1 3QR, UK.
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20
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Kattnig DR, Evans EW, Déjean V, Dodson CA, Wallace MI, Mackenzie SR, Timmel CR, Hore PJ. Chemical amplification of magnetic field effects relevant to avian magnetoreception. Nat Chem 2016; 8:384-91. [PMID: 27001735 DOI: 10.1038/nchem.2447] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 12/18/2015] [Indexed: 12/15/2022]
Abstract
Magnetic fields as weak as the Earth's can change the yields of radical pair reactions even though the energies involved are orders of magnitude smaller than the thermal energy, kBT, at room temperature. Proposed as the source of the light-dependent magnetic compass in migratory birds, the radical pair mechanism is thought to operate in cryptochrome flavoproteins in the retina. Here we demonstrate that the primary magnetic field effect on flavin photoreactions can be amplified chemically by slow radical termination reactions under conditions of continuous photoexcitation. The nature and origin of the amplification are revealed by studies of the intermolecular flavin-tryptophan and flavin-ascorbic acid photocycles and the closely related intramolecular flavin-tryptophan radical pair in cryptochrome. Amplification factors of up to 5.6 were observed for magnetic fields weaker than 1 mT. Substantial chemical amplification could have a significant impact on the viability of a cryptochrome-based magnetic compass sensor.
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Affiliation(s)
- Daniel R Kattnig
- Department of Chemistry, University of Oxford, Physical &Theoretical Chemistry Laboratory, Oxford OX1 3QZ, UK
| | - Emrys W Evans
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, UK
| | - Victoire Déjean
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, UK
| | - Charlotte A Dodson
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Oxford OX1 3TA, UK
| | - Mark I Wallace
- Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Oxford OX1 3TA, UK
| | - Stuart R Mackenzie
- Department of Chemistry, University of Oxford, Physical &Theoretical Chemistry Laboratory, Oxford OX1 3QZ, UK
| | - Christiane R Timmel
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, UK
| | - P J Hore
- Department of Chemistry, University of Oxford, Physical &Theoretical Chemistry Laboratory, Oxford OX1 3QZ, UK
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21
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Abstract
Within the framework of the radical pair mechanism, magnetic fields may alter the rate and yields of chemical reactions involving spin-correlated radical pairs as intermediates. Such effects have been studied in detail in a variety of chemical systems both experimentally and theoretically. In recent years, there has been growing interest in whether such magnetic field effects (MFEs) also occur in biological systems, a question driven most notably by the increasing body of evidence for the involvement of such effects in the magnetic compass sense of animals. The blue-light photoreceptor cryptochrome is placed at the centre of this debate and photoexcitation of its bound flavin cofactor has indeed been shown to result in the formation of radical pairs. Here, we review studies of MFEs on free flavins in model systems as well as in blue-light photoreceptor proteins and discuss the properties that are crucial in determining the magnetosensitivity of these systems.
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Affiliation(s)
- Emrys W. Evans
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Charlotte A. Dodson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK
| | - Kiminori Maeda
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Till Biskup
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, 79104 Freiburg, Germany
| | - C. J. Wedge
- Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Christiane R. Timmel
- Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
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22
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Kajita Y, Evans EW, Yasuda H. Reproductive responses of invasive and native predatory lady beetles (Coleoptera: Coccinellidae) to varying prey availability. Environ Entomol 2009; 38:1283-1292. [PMID: 19689911 DOI: 10.1603/022.038.0440] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
As adults, many predatory insects must adjust to a constantly changing prey environment while balancing between survival and reproduction. Two laboratory experiments were conducted to compare reproductive responses of females of two species of lady beetles, invasive Coccinella septempunctata L. and native C. transversoguttata richardsoni (Brown), in Utah alfalfa fields to varying availability of prey. When both lady beetles were placed immediately on experimental diets after being collected from the field (first experiment) and when they were provided excess prey for 14 d before being placed on experimental diets (second experiment), C. septempunctata produced more but individually smaller eggs than C. transversoguttata. Overall, however, in both experiments, C. septempunctata and C. transversoguttata responded similarly when they consumed pea aphids in varying amounts, by laying fewer and less viable eggs when fewer prey were consumed. In particular, the experiments provided no evidence that C. septempunctata converts pea aphids into eggs at a relatively higher rate than C. transversoguttata under limited prey availability. However, C. septempunctata had greater ability than C. transversoguttata to maintain body weight, even as they were producing eggs at low rates. This suggests that low aphid availability is less stressful for C. septempunctata, perhaps because it has more physiological ability than C. transversoguttata to assimilate pea aphid nutrients at low aphid availability. Such ability might contribute to the numerical dominance of the introduced C. septempunctata in alfalfa fields, which have supported low numbers of aphids in recent years.
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Affiliation(s)
- Y Kajita
- Department of Biology, Utah State University, Logan, UT 84322-5305, USA.
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Paisán-Ruíz C, Evans EW, Jain S, Xiromerisiou G, Gibbs JR, Eerola J, Gourbali V, Hellström O, Duckworth J, Papadimitriou A, Tienari PJ, Hadjigeorgiou GM, Singleton AB. Testing association between LRRK2 and Parkinson's disease and investigating linkage disequilibrium. J Med Genet 2006; 43:e9. [PMID: 16467219 PMCID: PMC2564648 DOI: 10.1136/jmg.2005.036889] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 07/27/2005] [Accepted: 07/28/2005] [Indexed: 11/03/2022]
Abstract
BACKGROUND We and others recently identified the gene underlying PARK8 linked Parkinson's disease (PD). This gene, LRRK2, contains mutations that cause an autosomal dominant PD, including a mutation, G2019S, which is the most common PD causing mutation identified to date. Common genetic variability in genes that contain PD causing mutations has previously been implicated as a risk factor for typical sporadic disease. METHODS We undertook a case-control association analysis of LRRK2 in two independent European PD cohorts using 31 tagging single nucleotide polymorphisms (tSNPs) and five potentially functional SNPs. To assess the structure of this locus in different populations, we have performed linkage disequilibrium (LD) analysis using these variants in a human diversity panel. RESULTS We show that common genetic variability in LRRK2 is not associated with risk for PD in the European populations studied here. We also show inter-population variability in the strength of LD across this locus. CONCLUSIONS To our knowledge this is the first comprehensive analysis of common variability within LRRK2 as a risk factor for PD.
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Johnson J, Hague SM, Hanson M, Gibson A, Wilson KE, Evans EW, Singleton AA, McInerney-Leo A, Nussbaum RL, Hernandez DG, Gallardo M, McKeith IG, Burn DJ, Ryu M, Hellstrom O, Ravina B, Eerola J, Perry RH, Jaros E, Tienari P, Weiser R, Gwinn-Hardy K, Morris CM, Hardy J, Singleton AB. SNCA multiplication is not a common cause of Parkinson disease or dementia with Lewy bodies. Neurology 2005; 63:554-6. [PMID: 15304594 DOI: 10.1212/01.wnl.0000133401.09043.44] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The authors recently have shown that triplication of the alpha-synuclein gene (SNCA) can cause Parkinson disease (PD) and diffuse Lewy body disease within the same kindred. The authors assessed 101 familial PD probands, 325 sporadic PD cases, 65 patients with dementia with Lewy bodies, and 366 neurologically normal control subjects for SNCA multiplication. The authors did not identify any subjects with multiplication of SNCA and conclude this mutation is a rare cause of disease.
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Affiliation(s)
- J Johnson
- Laboratory of Neurogenetics, National Institute on Aging, NIH, Bethesda, MD 20892, USA
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Owen EA, Evans EW. The effect of the occlusion of hydrogen on the characteristic temperature of palladium and the vibration amplitudes of its atoms. ACTA ACUST UNITED AC 2002. [DOI: 10.1088/0508-3443/18/5/308] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Wiekowski MT, Leach MW, Evans EW, Sullivan L, Chen SC, Vassileva G, Bazan JF, Gorman DM, Kastelein RA, Narula S, Lira SA. Ubiquitous transgenic expression of the IL-23 subunit p19 induces multiorgan inflammation, runting, infertility, and premature death. J Immunol 2001; 166:7563-70. [PMID: 11390512 DOI: 10.4049/jimmunol.166.12.7563] [Citation(s) in RCA: 226] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
p19, a molecule structurally related to IL-6, G-CSF, and the p35 subunit of IL-12, is a subunit of the recently discovered cytokine IL-23. Here we show that expression of p19 in multiple tissues of transgenic mice induced a striking phenotype characterized by runting, systemic inflammation, infertility, and death before 3 mo of age. Founder animals had infiltrates of lymphocytes and macrophages in skin, lung, liver, pancreas, and the digestive tract and were anemic. The serum concentrations of the proinflammatory cytokines TNF-alpha and IL-1 were elevated, and the number of circulating neutrophils was increased. In addition, ubiquitous expression of p19 resulted in constitutive expression of acute phase proteins in the liver. Surprisingly, liver-specific expression of p19 failed to reproduce any of these abnormalities, suggesting specific requirements for production of biologically active p19. Bone marrow transfer experiments showed that expression of p19 by hemopoietic cells alone recapitulated the phenotype induced by its widespread expression, pointing to hemopoietic cells as the source of biologically active p19. These findings indicate that p19 shares biological properties with IL-6, IL-12, and G-CSF and that cell-specific expression is required for its biological activity.
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Affiliation(s)
- M T Wiekowski
- Department of Immunology, Schering-Plough Research Institute, Kenilworth, NJ 07033, USA
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Freeman KP, Evans EW, Lester S. Quality control for in-hospital veterinary laboratory testing. J Am Vet Med Assoc 1999; 215:928-9. [PMID: 10511853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Affiliation(s)
- K P Freeman
- Animal Health Trust, Diagnostic Laboratory Services, Newmarket, Suffolk, England
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Leach MW, Frank DW, Berardi MR, Evans EW, Johnson RC, Schuessler DG, Radwanski E, Cartwright ME. Renal changes associated with naproxen sodium administration in cynomolgus monkeys. Toxicol Pathol 1999; 27:295-306. [PMID: 10356706 DOI: 10.1177/019262339902700305] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Naproxen sodium was administered to cynomolgus monkeys (Macaca fascicularis) by oral gavage at daily doses of 44, 88, or 176 mg/kg for 2 wk (2 monkeys/gender) or of 44 mg/kg for 13 wk (4 monkeys/gender). Body weight loss occurred in at least one monkey in all naproxen sodium-dosed groups in the 2-wk (up to 16% loss) and 13-wk (up to 22% loss) studies. Increases in plasma naproxen concentrations were dose proportional between 44 and 88 mg/kg but were less than dose proportional between 88 and 176 mg/kg. Up to 2-fold increases in creatinine and/or serum urea nitrogen values as well as higher renal weights occurred in monkeys receiving 176 mg/kg for 2 wk or 44 mg/kg for 13 wk. Microscopically, renal changes were observed in all naproxen sodium-dosed groups. Renal findings after 2 wk of exposure included increased interstitial ground substance, tubular dilatation, and tubulointerstitial nephritis; in the 13-wk study, cortical tubular atrophy and interstitial fibrosis were also observed. These studies identify the kidney as the target organ of naproxen sodium in cynomolgus monkeys.
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Affiliation(s)
- M W Leach
- Schering-Plough Research Institute, Lafayette, New Jersey 07848, USA.
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Abstract
Four avian heterophil antimicrobial cationic peptides (Chicken Heterophil Peptides 1 and 2, and Turkey Heterophil Peptides 1 and 3) were evaluated for in vitro microbicidal activity against selected avian pathogens and human pathogens which are harbored by birds. At concentrations of 16-2 micrograms/ml, all four avian peptides effected a greater than 90% reduction in the survival of Candida albicans, Salmonella enteriditis, and Campylobacter jejuni. None of the peptides, including the known antimicrobial peptide protamine (used as a positive control), were able to reduce the survival of Pasteurella multocida by 90% at the maximum peptide concentration (16 micrograms/ml) tested. At 16 micrograms/ml, the turkey peptide THP3 did not effect a 90% reduction in survival of Bordetella avium, Escherichia coli, or Salmonella typhimurium, while all of the other peptides tested were effective at this concentration or less. This peptide, THP3, does not share the same homologous amino acid sequence shared by the other three peptides. Under our experimental conditions, none of the peptides neutralized Infectious Bronchitis Virus, an enveloped coronavirus of chickens.
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Affiliation(s)
- E W Evans
- Department of Veterinary Pathology, University of Georgia, Athens, USA.
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Abstract
Five bactericidal peptides (chicken heterophil peptides CHP1 and CHP2; turkey heterophil peptides THP1, THP2, and THP3) were purified from avian heterophil granules. All peptides were cationic and rich in cysteine, arginine, and lysine. The complete amino acid sequence, consisting of 39 amino acids, was determined for CHP1. This peptide had a molecular weight of 4481 as determined by mass spectrometry. Partial NH2-terminal amino acid sequences were obtained for the remaining peptides. Both chicken peptides and THP1 shared sequence homology at 22 residues and a cysteine motif which was similar to that of bovine beta-defensins. THP2 and THP3 were homologous to each other but were not homologous to the other three and had a unique cysteine motif. Peptides CHP1, CHP2, and THP1 killed Staphylococcus aureus and Escherichia coli in vitro, whereas THP2 and THP3 killed only S. aureus in vitro.
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Affiliation(s)
- E W Evans
- Department of Veterinary Pathology, University of Georgia, Athens
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Evans EW, Burnett J, Bines JA. A study of the effect of exposure in the reticulo-rumen of the cow on the strength of cotton, grass, hay and straw. Br J Nutr 1974; 31:273-84. [PMID: 4835783 DOI: 10.1079/bjn19740036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
1. Changes in strength of cotton, Italian ryegrass leaf, hay stem and barley-straw stem on immersion in the contents of the reticulo-rumen, at two sites in the rumen and at one site in the reticulum, for periods of up to 56 h were measured using a cow on a hay diet. Specimens of the fibrous materials were immersed in the rumen digesta in such a way that they were not damaged by agitation or by rumination.2. Load-to-fracture and elongation were measured on a machine using a constant-speed cross-head at a strain of about 10−3/s. The ratio strength:density (breaking load/mass per unit length) was determined.3. Leaf of Italian ryegrass and stem of hay and of barley straw had strengths of about 37, 150 and 210 MN/m2. They lost strength at different rates when immersed in the rumen digesta, the times to half strength being in the ratio grass: hay: straw = 1:1.9:3.8. The similarity of this ratio to that for total time for eating and ruminating as given by Balch (1969), namely 1:2.0:3.5, for similar materials was noted.
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Evans EW, Pearce GR, Burnett J, Pillinger SL. Changes in some physical characteristics of the digesta in the reticulo-rumen of cows fed once daily. Br J Nutr 1973; 29:357-76. [PMID: 4715148 DOI: 10.1079/bjn19730114] [Citation(s) in RCA: 91] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
1. Three cows were given 3, 5 or 7 kg hay once daily in a Latin-square design, and samples of digesta from four sites in the rumen and one site in the reticulum were taken at six times within the 24 h period after the feed. Dry-matter content and distribution of particle size and of particle density were measured for each sample. The changes in these measurements with time were studied. The incidence of rumination was also recorded.2. Dry-matter contents of samples ranged from 15 to 3%. Values for samples from the dorsal sacs of the rumen were considerably higher than those for samples from the ventral sites; they also changed more with time after feeding and with level of feeding.3. Particles were fractionated by sieving into six size groups with mean dimensions (mm) of 9·3 × 0·8, 4·4 × 0·6, 2·6 × 0·3, 1·6 × 0·25, 0·5 × 0·1 and smaller than 0·5 × 0·1. Coarse particles occurred at highest concentrations in the dorsal sacs of the rumen and responded to effects of time and level of feeding; smaller particles showed less response.4. Particle densities ranged from 800 g/l to 1500 g/l. The proportions of low-density particles were higher in samples from the dorsal sacs of the rumen than in samples from ventral sites; the latter samples had higher proportions of high-density particles than of low-density particles. The changes which occurred are discussed.5. The density of coarse particles tended to be low and that of fine particles tended to be high.6. Rumination started at the time of maximum concentration of particles of low density and minimum concentration of particles of high density. Conversely, rumination ended when the concentration of the low-density particles was a minimum and that of the dense particles a maximum.7. The results are discussed in relation to the possible movement of particles within the reticulo-rumen and the kinetics of particle breakdown.
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Abstract
The results of surgery for carcinoma of the bronchus among an elderly population are reviewed in relation to the total number of cases seen. Although there is a 20% operative hospital mortality, nevertheless a survival rate of 39% for four years makes surgery in the elderly worthwhile. The span of life in untreated cases is even less than in the younger age groups.
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