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Noboru Mataga - One of the best experts on this subject based on the ideXlab platform.
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photoinduced electron transfer in wild type and mutated flavodoxin from desulfovibrio vulgaris strain miyazaki f Energy Gap law
Journal of Photochemistry and Photobiology A-chemistry, 2011Co-Authors: Kiattisak Lugsanangarm, Somsak Pianwanit, Sirirat Kokpol, Fumio Tanaka, Haik Chosrowjan, Seiji Taniguchi, Noboru MatagaAbstract:Abstract Time–dependent changes in the geometrical factors near the isoalloxazine (Iso) residue of FMN in three mutant isoforms [Y97F, W59F and W59F–Y97F (DM, double mutation)] of the flavodoxin (FD) from Desulfovibrio vulgaris , strain Miyazaki F., were obtained by molecular dynamic (MD) simulation. The center to center distances from Iso to Trp59 in Y97F and to Tyr97 in W59F were 0.78 nm and 0.55 nm, respectively. The remarkable fluorescence quenching in these proteins has been explained in terms of photoinduced electron transfer (ET) from the Trp59 and/or Tyr97 residues to the excited isoalloxazine (Iso*). The ultrafast fluorescence dynamics of the wild type (WT) and the Y97F, W59F and DM variant FDs reported by Mataga et al. (J. Phys. Chem. B 106 (2002) 8917–8920), were simultaneously analyzed by the electron transfer theory of Kakitani and Mataga (KM theory) and the atomic coordinates determined by MD, according to a non-linear least squares method. Agreements between the observed and calculated decays were all very good. The obtained physical constants contained in the KM theory were, for Trp and Tyr, respectively, a frequency factor ( ν 0 ) of 3.09 × 10 3 ps −1 and 2.46 × 10 3 ps −1 , an ET process coefficient ( β ) of 55.6 nm −1 and 9.64 nm −1 , a critical transfer distance ( R 0 ) of 0.772 nm and 0.676 nm, plus a free Energy related to the electron affinity of Iso* ( G Iso 0 ) of 7.67 eV. These constants were common to all three mutant FD systems. In contrast, the static dielectric constant depended on the FD systems, being 4.78, 4.04 and 2.28 in the Y97F, W59F and DM variant FDs, respectively. The mean ET rate to Iso* was fastest from Trp59 in Y97F among the three systems. The total free Energy Gap in the FD systems was obtained as a sum of the net electrostatic ( ES ) Energy between ion pairs and the standard free Energy Gap. A plot of ln k ET / λ S vs. − Δ G T 0 / λ S in all ET donors, where k ET is ET rate, λ S is the reorganization Energy and Δ G T 0 is the total free Energy Gap, revealed that ln k ET / λ S can be expressed by a parabolic function of − Δ G T 0 / λ S and the ET process in FD took place mostly in the normal region.
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examination of the viability of the collins kimball model and numerical calculation of the time dependent Energy Gap law of photoinduced charge separation in polar solution
Principles and Practice of Constraint Programming, 1995Co-Authors: N Matsuda, Toshiaki Kakitani, T Denda, Noboru MatagaAbstract:Abstract Viability of the analysis using the Collins-Kimball model for the rate constant of photoinduced charge separation reactions in polar solutions is investigated. In the Collins-Kimball model, it is assumed that the reaction occurs only at a specified distance in the encounter between donor and acceptor molecules under mutual diffusional motion while in real systems the reaction can occur over a range of distances. By comparing the fluorescence decay curve obtained by the Collins-Kimball model with the decay curve calculated numerically using the model incorporating a suitable distance dependence of the reaction rate, we found that the Collins-Kimball model is viable with some reservation. Using the numerically calculated distance distribution function of donor and acceptor molecules, we calculated time-dependent Energy Gap laws of photoinduced charge separation reactions. The calculated Energy Gap law for t = 0 fits well the experimental data obtained by a transient effect analysis of the fluorescence decay curve (S. Nishikawa, T. Asahi, T. Okada, N. Mataga and T. Kakitani, Chem. Phys. Letters 185 (1991) 237). The calculated Energy Gap law for t → ∞ fits very well the experimental data obtained by the stationary state fluorescence quenching measurements (D. Rehm and A. Weller, Israel J. Chem. 8 (1970) 259).
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effects of the donor acceptor distance distribution on the Energy Gap laws of charge separation and charge recombination reactions in polar solutions
The Journal of Physical Chemistry, 1992Co-Authors: Toshiaki Kakitani, Akira Yoshimori, Noboru MatagaAbstract:The Energy Gap laws of charge separation (CS) and charge recombination (CR) are analyzed in terms of donor-acceptor distance distribution in this paper. The Energy Gap dependence of the CS reaction rate constant, which has a large and flat shape, is explained. Close contact of the donor-acceptor (D-A ms) molecules cause the sharp increase in the normal region. The large mutual distances of the donor-acceptor molecules cause the flat shapes of the top and inverted regions. The bell-shaped CR Energy Gap law is due to the narrow distance distribution of the germinate radical ion pair produced by the photoinduced CS reaction. 35 refs., 6 figs., 1 tab.
Tracey M Clarke - One of the best experts on this subject based on the ideXlab platform.
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synthesis and exciton dynamics of donor orthogonal acceptor conjugated polymers reducing the singlet triplet Energy Gap
Journal of the American Chemical Society, 2017Co-Authors: David M E Freeman, Andrew J Musser, Jarvist M Frost, Hannah L Stern, Alexander K Forster, Kealan J Fallon, Alexandros G Rapidis, Franco Cacialli, Iain Mcculloch, Tracey M ClarkeAbstract:The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the Energy Gap between triplets and “bright” singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this Gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet–triplet Energy Gap in fully conjugated polymers, using a donor–orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange Energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-stat...
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synthesis and exciton dynamics of donor orthogonal acceptor conjugated polymers reducing the singlet triplet Energy Gap
Journal of the American Chemical Society, 2017Co-Authors: David M E Freeman, Andrew J Musser, Jarvist M Frost, Hannah L Stern, Alexander K Forster, Kealan J Fallon, Alexandros G Rapidis, Franco Cacialli, Iain Mcculloch, Tracey M ClarkeAbstract:The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the Energy Gap between triplets and “bright” singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this Gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet–triplet Energy Gap in fully conjugated polymers, using a donor–orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange Energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-stat...
David M E Freeman - One of the best experts on this subject based on the ideXlab platform.
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synthesis and exciton dynamics of donor orthogonal acceptor conjugated polymers reducing the singlet triplet Energy Gap
Journal of the American Chemical Society, 2017Co-Authors: David M E Freeman, Andrew J Musser, Jarvist M Frost, Hannah L Stern, Alexander K Forster, Kealan J Fallon, Alexandros G Rapidis, Franco Cacialli, Iain Mcculloch, Tracey M ClarkeAbstract:The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the Energy Gap between triplets and “bright” singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this Gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet–triplet Energy Gap in fully conjugated polymers, using a donor–orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange Energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-stat...
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synthesis and exciton dynamics of donor orthogonal acceptor conjugated polymers reducing the singlet triplet Energy Gap
Journal of the American Chemical Society, 2017Co-Authors: David M E Freeman, Andrew J Musser, Jarvist M Frost, Hannah L Stern, Alexander K Forster, Kealan J Fallon, Alexandros G Rapidis, Franco Cacialli, Iain Mcculloch, Tracey M ClarkeAbstract:The presence of energetically low-lying triplet states is a hallmark of organic semiconductors. Even though they present a wealth of interesting photophysical properties, these optically dark states significantly limit optoelectronic device performance. Recent advances in emissive charge-transfer molecules have pioneered routes to reduce the Energy Gap between triplets and “bright” singlets, allowing thermal population exchange between them and eliminating a significant loss channel in devices. In conjugated polymers, this Gap has proved resistant to modification. Here, we introduce a general approach to reduce the singlet–triplet Energy Gap in fully conjugated polymers, using a donor–orthogonal acceptor motif to spatially separate electron and hole wave functions. This new generation of conjugated polymers allows for a greatly reduced exchange Energy, enhancing triplet formation and enabling thermally activated delayed fluorescence. We find that the mechanisms of both processes are driven by excited-stat...
Anthony Krier - One of the best experts on this subject based on the ideXlab platform.
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Photoreflectance study of N- and Sb-related modifications of the Energy Gap and spin-orbit splitting in InNAsSb alloys
Applied Physics Letters, 2011Co-Authors: Robert Kudrawiec, Jan Misiewicz, Qiandong Zhuang, A. M. R. Godenir, M. Latkowska, Anthony KrierAbstract:Photoreflectance spectroscopy has been used to study the Energy Gap and spin-orbit splitting in InNAsSb alloys containing different amounts of nitrogen and antimony. It has been observed that nitrogen mainly affects the conduction band, without having any influence on the spin-orbit splitting, whereas antimony significantly modifies the spin-orbit splitting. The N- and Sb-related modifications to the band structure lead to alloys which have a spin orbit splitting larger than the Energy Gap. Consequently, InNAsSb alloys are very promising for use in optoelectronic devices since they offer a route towards the reduction of non-radiative Auger recombination.
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Photoreflectance study of the Energy Gap and spin-orbit splitting in InNAs alloys
Applied Physics Letters, 2009Co-Authors: Robert Kudrawiec, Jan Misiewicz, Qiandong Zhuang, A. M. R. Godenir, Anthony KrierAbstract:Photoreflectance spectroscopy has been applied to study the Energy Gap and the spin-orbit splitting in InNAs alloys with the nitrogen concentration changing from 0% to 0.88%. It has been observed that the Energy Gap of InNAs decreases with the increase in nitrogen concentration (about 60 meV per 1% of nitrogen) but the spin-orbit splitting almost does not change. It shows that nitrogen atoms in InNAs alloys influence mainly the conduction band, i.e., shift this band toward the valence band. The bowing parameter for the Energy Gap and spin-orbit splitting has been determined to be 7.3 +/- 0.6 and -0.7 +/- 0.4 eV, respectively.©2009 American Institute of Physics
E Bauer - One of the best experts on this subject based on the ideXlab platform.
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evidence for line nodes in the superconducting Energy Gap of noncentrosymmetric cept3si from magnetic penetration depth measurements
Physical Review Letters, 2005Co-Authors: I Bonalde, Werner Bramerescamilla, E BauerAbstract:We report measurements of the magnetic penetration depth lambda(T) in high-quality CePt3Si samples down to 0.049 K. We observe a linear temperature dependence below T approximately equal to 0.16Tc, which is interpreted as evidence for line nodes in the Energy Gap of the low-temperature phase of this material. A kink in lambda(T) at about 0.53 K may be associated with the second superconducting transition recently reported. The results are discussed in terms of the symmetry of the superconducting order parameter.
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evidence for line nodes in the superconducting Energy Gap of noncentrosymmetric cept3si from magnetic penetration depth measurements
Physical Review Letters, 2005Co-Authors: I Bonalde, Werner Bramerescamilla, E BauerAbstract:We report measurements of the magnetic penetration depth $\ensuremath{\lambda}(T)$ in high-quality ${\mathrm{CePt}}_{3}\mathrm{Si}$ samples down to 0.049 K. We observe a linear temperature dependence below $T\ensuremath{\simeq}0.16{T}_{c}$, which is interpreted as evidence for line nodes in the Energy Gap of the low-temperature phase of this material. A kink in $\ensuremath{\lambda}(T)$ at about 0.53 K may be associated with the second superconducting transition recently reported. The results are discussed in terms of the symmetry of the superconducting order parameter.
