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University of Pennsylvania, “Spectroscopic and Dynamical Studies of Excitations on Polysilane Chains”. I I . Monolayers. Chairman, D. Whitten, University of Rochester, D. Mobius, Max-Planck-Institute for Biophysical Chemistry, Gottingen, “Formation of Charge Transfer Complexes and Photoinduced Electron Transfer in Monolayers”; C. Chidsey, AT&T Bell Laboratories, “Long-Distance Electron Transfer at the Metal-Electrolyte Interface Probed in Electroactive, SelfAssembled Monolayers”; M. Fujihira, Tokyo Institute of Technology, “Photoinduced Electron Transfer in Langmuir-Blodgett Films”; H. Abruna, Cornell University, “Solvent Effects on the Electron Transfer and Formal Potential of a Redox Active Self-Assembling Monolayer”; T. L. Penner, Eastman Kodak Co., “Medium Effects on Photoinduced Electron Transfer in Langmuir-Blodgett Films”. Discussion lead by Dietmar Mobius. III. Novel Confined Systems. Chairman, A. Marchetti, Eastman Kodak Co. S. Mukamel, University of Rochester, “Optical Nonlinearities in Molecular Aggregates: Cooperativity and Coherence Size”; D. Beratan, California Institute of Technology, “Protein Electron Transfer; hot Spots, cold Spots, and Secondary Structure Dependence Predictions from Tunneling Pathway Calculations”; T. Mallouk, The University of Texas at Austin, “Light-Induced Electron Transfer Reactions in Zeolites”; A. Kuki, Cornell University, “Electronic Interactions Between Custom Aromatic Amino Acids Embedded Within Peptides of de nouo Design”; R. J. D. Miller, University of Rochester, “Ultrafast Surface Reaction Dynamics: Mapping the Electron Trajectory”. Discussion lead by John Tully. IV Conjugated Polyenes. Chairman, K. Yoshihara, Institute for Molecular Science; N. Mataga, Osaka University, “Dynamics and Mechanisms of Photoinduced Charge Separation in Donor Acceptor Systems Combined by Spacers and Confined in Polymer Systems”; B. Kohler, University of California, Riverside, ”Electronic Structure of Donor or Acceptor Substituted Linear Polyenes”; H. Mizes, Xerox Webster Research Center, “Transport in Ladder Polymers”; W.-P. Su,University of Houston, “Nonlinear
Optical Susceptibilities of Excitons in Conjugated Polymers”; S. E. Etemad, Bell Communications, “Nonlinear Optical Spectroscopy of Conjugated Polymers”. Discussion lead by Bryan Kohler. V. Semiconductor Microcrystallites. Chairman, E. Conwell, Xerox Webster Research Center. M. A. Fox, University of Texas at Austin, “Photocatalysis on Semiconductor Clusters Inside Inert Supports”; T. Itoh, Tohoku University, ”Linear and Nonlinear Optical Properties of Excitons in CuCl Microcrystals”; T. Kobayashi, University of Tokyo, “Temperature Dependence of the Superradiative Lifetime of CdS Microcrystallites”; L. B m , AT&T Bell Labs., “Electron-hole Dynamics in Quantum Semiconductor Crystallites”; C. Flytzanis, Laboratoire d’Optique Quantique du C.N.R.S., France, “Impact of Quantum Confinement on Optical Nonlinearities”. Discussion lead by Marye Anne Fox. VI. Quantum Wells. Chairman, A. Muenter, Eastman Kodak Co. D. S. Chemla, Lawrence Berkeley Lab, “Exciton-exciton Interaction in Quasi-2 Dimensional Structures” and “Nonlinear Optical Response of Magnetically Confined Excitons”; S. R. Forrest, University of Southern California, “The Optical Properties of Crystalline Organic Multiple Quantum Well Structures”; A. J. Nozik, Solar Energy Research Institute, “Electron Transfer vs Relaxation in Photoexcited Quantum Wells”; G. L. McLendon, University of Rochester, “Electron-Hole Trapping and Recombination in Silver Bromide “Quantum Dots”. Discussion lead by Daniel S. Chemla. The generous support of The National Science Foundation, The Office of Naval Research, The University of Rochester, Eastman Kodak Co., and Xerox Corp. is greatly appreciated. I would like to extend special thanks to Peter Schmidt, Peter Reynolds, and Michael Shlesinger of the ONR for their efforts which made the participation of many graduate students and young scientists possible. The enthusiasm and efforts of Mostafa El Sayed and Welford Castleman, Jr., who arranged for this special issue and its timely publication, are most appreciated.
Picosecond Kinetics of Light-Induced Electron Transfer from J-Aggregated Cyanine Dyes to AgBr Microcrystals: Effect of Aggregate Size Tadaaki Tani,*,+Takeshi Suzumoto,t Klaus Kemnitz,f and Keitaro Yoshiharaf Ashigara Research Laboratories, Fuji Photo Film Company, Ltd., Mimami- Ashigara, Kanagawa 250-01, Japan, and Institute for Molecular Science, Myodaiji, Okazaki 444, Japan (Received: September 23, 1991, In Final Form: December 16, 1991)
The light-induced electron transfer from 5,5’-dichloro-9-ethylthiacarbocyanine(dye 1) and related dyes to octahedral silver bromide microcrystals was studied in a photographic emulsion (Le., a suspension of the microcrystals in an aqueous gelatin matrix). The energy gap dependence of the quantum yield of electron transfer [4r= k , / ( k , + kL),where k, and kL are the rate constants of the electron transfer and competing deactivation channels, respectively] obeyed the Marcus theory with a very small total rearrangement energy of 0.05 eV. The aggregate size of dye 1 on the microcrystalswas increased by increasing the agitation temperature of the emulsion. The effect of the aggregate size on the kinetics of electron transfer was studied by means of a time-correlated single-photon-counting system. The film samples were scanned at several centimeters per second to avoid photoinduced damage. For a J-aggregate consisting of -6 molecules, &, k,, and kL were 0.44, 1.69 X loLo s-l, and 2.17 X loios-I, respectively, and for a larger J-aggregate of 14 molecules, we obtained 0.20, 1.03 X loLos-l, and 4.23 X loios-l, respectively. It is thought that the proportionality of the radiative rate constant of the J-aggregate to its size, as given by exciton theory, made a substantial contribution to the increase in kL and to the decrease in & with aggregate size. The decrease in k, with aggregate size is consistent with the mechanism of exciton-trapping supersensitization.
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I. Introduction Silver halide microcrystals, which are used as photosensitive elements in photographic materials, are intrinsically sensitive only to blue light in the visible region, Spectral sensitization is a Ashigara Research Laboratories. of Molecular Science.
t Institute
0022-365419212096-2778$03.00/0
technology that makes photographic materials sensitive to green and red light by Putting sensitizing dyes on the surface of the microcrystals. Spectral sensitization is Used, therefore, in almost all Photographic materials and is one of the most important technologies that determine photographic sensitivity. Based on accumulated knowledge of the correlation between photographic activities and electronic energy levels of the frontier 0 1992 American Chemical Society
The Journal of Physical Chemistry, Vol. 96, No. 7, 1992 2779
Electron Transfer from Cyanine Dyes to AgBr TABLE I: Dyes Studied in This Paper w 4 m f & C H
-Z-CH
N
w3
I "X
I
R
dye 1 2 3 4 5 6 7 8 9 10
R CiH,SO,Ei Et C3H6SOC C4 H 8 S03Et Et Et Et CIH6SOc Et "
