Faculty Profiles - AKIYAMA Tsuyoshi

Papers - AKIYAMA Tsuyoshi

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Structural characterization and photoelectrochemical properties of the self-assembled monolayers of tris(2,2′-bipyridine)ruthenium(II)-viologen linked compounds formed on the gold surface Reviewed

Terasaki N., Akiyama T., Yamada S.

Langmuir 18 ( 22 ) 8666 - 8671 2002.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

Steady-state spectroscopic studies of tris(2,2′-bipyridine)ruthenium(II)-viologen (Ru -V ) linked thiol derivatives with different spacer-chain lengths (denoted as RuC VC S, where (n, m) = (11, 2), (7, 6), (7, 2), and (3, 6)) and different number ratios of Ru :V = 1:2, Ru(C VC S), have been carried out, together with the corresponding reference compounds without Ru or V . Absorption and cyclic voltammetric (CV) measurements indicated no appreciable electronic interactions between the two chromophores (Ru and V ) in the ground state. While luminescence spectral measurements revealed the occurrence of efficient photoinduced electron transfer from the photoexcited Ru (*Ru ) to V . The electron transfer efficiency was also better for the 1:2 complex as compared with the corresponding 1:1 complex. Self-assembled monolayers (SAMs) of these compounds were fabricated on a gold electrode. XPS and CV measurements revealed immobilization of the compounds on the gold surface via gold-sulfur bonding. In the presence of triethanolamine, all modified electrodes with the Ru -V linked compounds showed clear anodic photocurrents. The presence of the V moiety was crucial for obtaining larger photocurrents A shorter spacer-chain length between the V moiety and the terminal thiol group (m = 2) afforded a larger photocurrent, while a moderate spacer-chain length between the Ru and the V moieties was also a key for obtaining a larger photocurrent. A possible mechanism for photocurrent generation is discussed. 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ n m 7 6

DOI： 10.1021/la025936v

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Novel photoelectrochemical cell using a self-assembled monolayer of a ruthenium (II) tris(2,2′-bipyridine) thiol derivative Reviewed

Akiyama T., Inoue M., Kuwahara Y., Yamada S.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 41 ( 7 A ) 4737 - 4738 2002.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

A novel thin-layer two-electrode photoelectrochemical cell consisting of a self-assembled monolayer of a ruthenium (II) tris(2,2′-bipyridine) thiol derivative on a transparent indium tin oxide (ITO) electrode and a bare ITO electrode was fabricated, and exhibited satisfactory performance as a photocell. A ruthenium (II) tris(2,2′-bipyridine)-viologen (electron donor-acceptor) pair yielded a higher performance of the photocell than the ruthenium complex (donor) moiety alone. Photoinduced electron transfer from the photoexcited ruthenium complex moiety to the viologen moiety was quite effective for generating larger photocurrents.

DOI： 10.1143/jjap.41.4737

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Facile fabrication of photoelectrochemical assemblies consisting of gold nanoparticles and a tris(2,2′-bipyridine)ruthenium(II)-viologen linked thiol Reviewed

Kuwahara Y., Akiyama T., Yamada S.

Langmuir 17 ( 19 ) 5714 - 5716 2001.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

Facile fabrication of a modified electrode with gold nanoparticles and a tris(2,2′-bipyridine)ruthenium(II)-viologen linked thiol (RuVS) is described. First, the gold nanoparticles (14 ± 1 nm) were precipitated onto the gold electrode in an aqueous solution. Then, this electrode was immersed into a acetonitrile solution containing RuVS, to immobilize it via Au-S bonding. Scanning electron micrographs show agglomeration and island formation of the gold particles on the electrode and 1-3 μm thickness of the deposition. In cyclic voltammetry, a redox couple due to one-electron reduction of the viologen moiety was clearly observed and its intensity increased with increasing the extent of deposition. The anodic photocurrent from the modified electrode ascribed to ruthenium-complex-sensitized redox cycles was clearly observed and was more than 15-fold larger as compared with that of the flat electrode (without gold particles).

DOI： 10.1021/la010566g

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Construction of gold nanoparticle-ruthenium (II) tris(2,2′-bipyridine) self-assembled multistructures and their photocurrent responses Reviewed

Kuwahara Y., Akiyama T., Yamada S.

Thin Solid Films 393 ( 1-2 ) 273 - 277 2001.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Thin Solid Films

Three-dimensional multistructure assemblies consisting of gold nanoparticles and a sulfur-containing ruthenium (II) tris(2,2-bipyridine) derivative were fabricated on an ITO electrode by their alternate self-assembling. Absorption spectra of the assemblies showed immobilization of the gold surface and the ruthenium complex. Broadening and red shift of the plasmon band were observed by increasing the number of assembled layers, which revealed the presence of interparticle plasmon coupling. In the presence of triethanolamine as a sacrificial reducing agent, photocurrent responses from the multistructure assemblies were clearly observed in the anodic direction. The photocurrent increased with increasing the number of assembled layers. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0040-6090(01)01085-9

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Fabrication of porphyrin-titanium oxide-fullerene assemblies on an ITO electrode and their photocurrent responses Reviewed

Akiyama T., Miyazaki A., Sutoh M., Ichinose I., Kunitake T., Yamada S.

Colloids and Surfaces A: Physicochemical and Engineering Aspects 169 ( 1-3 ) 137 - 141 2000.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Colloids and Surfaces A: Physicochemical and Engineering Aspects

A porphyrin-fullerene assembly via titanium oxide coordinative bonding was constructed on an ITO electrode, by using the techniques of self-assembly and the surface sol-gel process. In the presence of triethanolamine, clear photocurrent responses from the modified electrode were observed in the anodic direction, and they were much larger than the electrodes modified with the porphyrin or the fullerene alone. It is suggested that the photocurrent is ascribed to photoinduced charge separation between the porphyrin and the fullerene moieties. (C) 2000 Elsevier Science B.V.

DOI： 10.1016/S0927-7757(00)00426-X

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Facile construction of an ultra-thin [60]fullerene layer from [60]fullerene-homooxacalix[3]arene complexes on a gold surface Reviewed

Hatano T., Ikeda A., Akiyama T., Yamada S., Sano M., Kanekiyo Y., Shinkai S.

Journal of the Chemical Society. Perkin Transactions 2 ( 5 ) 909 - 912 2000.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of the Chemical Society. Perkin Transactions 2

A hexacationic homooxacalix[3]arene-[60]fullerene 2:1 complex can be deposited on an anion-coated gold surface as a monolayer (or at least as a monolayer-like ultra-thin film); as expected, this membrane efficiently shows a redox response in cyclic voltammetry and a photoelectrochemical response under visible light irradiation.

DOI： 10.1039/b000022l

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Preparation and photoelectrochemical properties of a self-assembled monolayer of a ruthenium tris(2,2′'-bipyridine)-viologen 1:2 linked compound Reviewed

Terasaki N., Akiyama T., Yamada S.

Chemistry Letters ( 6 ) 668 - 669 2000.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters

A ruthenium tris(2,2′-bipyridine)-viologen 1:2 linked disulfide was prepared. A gold electrode modified with this compound showed a higher efficiency of photocurrent as compared with a corresponding 1:1 linked compound.

DOI： 10.1246/cl.2000.668

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Effects of spacer-chain length on the photoelectrochemical responses of monolayer assemblies with ruthenium tris(2,2′-bipyridine) - viologen linked disulfides Reviewed

Koide Y., Terasaki N., Akiyama T., Yamada S.

Thin Solid Films 350 ( 1 ) 223 - 227 1999.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Thin Solid Films

Photochemical and photoelectrochemical properties of ruthenium tris(2,2′-bipyridine) (Ru )-viologen (V ) linked disulfides [RuCnVC S] (n (number of methylene groups) = 3, 7) with different spacer-chain lengths and Ru disulfides [RuC S] (m = 13, 17) were compared. The luminescence intensity in CH CN was in the order of [RuC S] ≈[RuC S] >[RuC VC S] ≫[RuC VC S] , implying efficient photoinduced electron-transfer between Ru and V moieties in the linked compounds. The monolayer assembly of the compound was fabricated on a gold surface. In the presence of triethanolamine, the anodic photocurrent was clearly observed from the RuC VC S/Au (n = 3, 7) electrode (gold electrode modified with [RuCnVC S] ), and its intensity was substantially larger for n = 7 than for n = 3. Photocurrent action spectra for the RuC VC S/Au (n = 3, 7) electrodes were well correlated with the corresponding electronic absorption spectra in solution. The photocurrent from the RuC VC S/Au electrode was reduced more effectively by the coexistence of a water-soluble viologen as compared with the RuC VC S/Au electrode. The photocurrent from the RuC S/Au (m = 13, 17) electrode was very small. The results suggest that the spacer-chain length between the Ru and the V moieties profoundly affects the Ru -sensitized photocurrent. 2+ 2+ 2+ 2+ 2+ 2+ 2+ 2+ 6 2 m 2 3 13 2 17 2 7 6 2 3 6 2 n 6 6 2 n 6 7 6 3 6 m

DOI： 10.1016/S0040-6090(99)00228-X

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Organic photoelectrochemical cell mimicking photoinduced multistep electron transfer in photosynthesis: Interfacial structure and photoelectrochemical properties of self-assembled monolayers of porphyrin- linked fullerenes on gold electrodes Reviewed

Imahori H., Ozawa S., Ushida K., Takahashi M., Azuma T., Ajavakom A., Akiyama T., Hasegawa M., Taniguchi S., Okada T., Sakata Y.

Bulletin of the Chemical Society of Japan 72 ( 3 ) 485 - 502 1999.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Bulletin of the Chemical Society of Japan

Self-assembled monolayers (SAMs) technique has been applied to porphyrin-linked fullerene systems to mimic supramolecular photoinduced charge-separation (CS) events in photosynthesis. Porphyrin-linked C molecules with a sulfide group were designed to self-assemble on a gold surface using S-Au interaction. The structure of the SAMs formed on gold electrodes was investigated by spectroscopic methods including X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)-visible spectroscopic ellipsometry, UV-visible absorption spectroscopy, and Fourier transform infrared (FTIR) spectroscopy as well as electrochemical studies. These results indicate that the SAMs have loosely packed structure; the porphyrin- C molecules are tilted and nearly parallel onto the gold surface. Short- circuit photocurrent with a level of sub-μA cm was observed for the photoelectrochemical cell in the presence of methylviologen (MV) under illumination with ca. 4 mW cm . The maximum intensity of the photocurrent in free-base porphyrin-C system is five times larger than that in the corresponding free-base porphyrin system, indicating that C is an effective mediator in multistep electron transfer (ET) processes. A possible mechanism for the photocurrent generation is discussed in terms of the photodynamics of porphyrin-linked fullerenes in solution. 60 60 60 60 -2 -2

DOI： 10.1246/bcsj.72.485

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Structure and photoelectrochemical properties of porphyrin-linked fullerenes on gold surface using self-assembled monolayer technique Reviewed

Imahori H., Azuma T., Ushida K., Takahashi M., Akiyama T., Hasegawa M., Okada T., Sakata Y.

Proceedings of SPIE - The International Society for Optical Engineering 3142 104 - 111 1997.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Proceedings of SPIE - The International Society for Optical Engineering

Self-assembled monolayers (SAMs) have recently attracted much attention as a new methodology among a variety of thin film preparation. There have been several reports of fullerene SAM. These fullerene thin films seem to be the most promising candidates for realizing photovoltaic and optoelectronic devices at the nano-scale level. We have applied this technique to donor-linked fullerene systems and have developed supramolecular porphyrin-C molecules that are designed to be self-assembled on gold surface. Such systems are expected to mimic supramolecular photoinduced charge-separation events in photosynthesis. Porphyrin-linked C bearing a methylthio group was prepared by 1,3-dipolar cycloaddition of the azomethine ylide porphyrin with C . SAM was formed by soaking Au electrode into a CH Cl solution of the porphyrin-C dyad. Structure of the SAM was investigated by spectroscopic methods including X-ray photoelectron spectroscopy (XPS) and ellipsometry and electrochemical studies. The large photocurrent with a level of sub-μA/cm was observed for the photochemical cell in the presence of methyl viologen under illumination with ∼10 mW/cm . Possible mechanism for the photocurrent generation is discussed in terms of the photodynamics of porphyrin-linked fullerenes. 60 60 60 2 2 60 2 2

DOI： 10.1117/12.279246

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MOLECULAR ASSEMBLIES OF PORPHYRINS ON GOLD SURFACE AND THEIR PHOTOPHYSICAL PROPERTIES

Tsuyoshi AKIYAMA

1997.3

Control of electron transfer and its utilization Reviewed

Sakata Y., Imahori H., Tsue H., Higashida S., Akiyama T., Yoshizawa E., Aoki M., Yamada K., Hagiwara K., Taniguchi S., Okada T.

Pure and Applied Chemistry 69 ( 9 ) 1951 - 1956 1997.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Pure and Applied Chemistry

In order to get information on the controlling factors of photosynthetic electron transfer and to apply the principle for the construction of artificial photosynthesis and molecular electronics, we have so far prepared various model compounds from which particular factors can be extracted. Among them our recent results on 1) mutual orientation effect, 2) effect of the nature of intervening bonds, 3) effect of inserted π-system, 4) effect of coordination bond between a redox pair, 5) size and shape effect of an acceptor, are described. In order to utilize charge separated state, C60-linked porphyrin with SMe group at the terminal position was synthesized and fixed it on gold surface using S-Au bond as self-assembled monolayer. When the sample was irradiated, photocurrent was observed.

DOI： 10.1351/pac199769091951

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The small reorganization energy of C<inf>60</inf> in electron transfer Reviewed

Imahori H., Hagiwara K., Akiyama T., Aoki M., Taniguchi S., Okada T., Shirakawa M., Sakata Y.

Chemical Physics Letters 263 ( 3-4 ) 545 - 550 1996.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Physics Letters

Porphyrin-linked fullerene 1 and porphyrin-linked quinone 2 have been designed and synthesized to evaluate the size and shape effect of fullerene in electron transfer. For evaluation of such an effect C and benzoquinone with comparable reduction potentials have been chosen and linked with a porphyrin, where a relatively rigid spacer ensures similar separation distance and nature of the intervening bonds between the redox pair. Accelerated charge separation and decelerated charge recombination were observed in 1 compared with 2 by picosecond fluorescence lifetime measurements and time-resolved transient absorption spectroscopy. They may be explained by the smaller reorganization energy in C compared with those in small acceptors. 60 60

DOI： 10.1016/s0009-2614(96)01244-4

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Linkage and solvent dependence of photoinduced electron transfer in zincporphyrin-C<inf>60</inf> dyads Reviewed

Imahori H., Hagiwara K., Aoki M., Akiyama T., Taniguchi S., Okada T., Shirakawa M., Sakata Y.

Journal of the American Chemical Society 118 ( 47 ) 11771 - 11782 1996.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of the American Chemical Society

Four different kinds of C -linked zincporphyrins have been prepared by changing systematically the linking position at meso-phenyl ring from ortho to para and their photophysical properties have been investigated. Regardless of the linkage between the two chromophores, photoinduced charge separation (CS) and subsequent charge recombination (CR) were observed in a series of zincporphyrin-C dyads by picosecond fluorescence lifetime measurements and time-resolved transient absorption spectroscopy. In THF the CS occurs from both the excited singlet state of the porphyrin and the C moieties, implying that the increase of the absorption cross section by both the chromophores results in the efficient formation of the ion pair (IP) state. On the other hand, in benzene the IP state generated by the photoinduced CS from the excited singlet state of the porphyrin to the C produces or energetically equilibrates with the locally excited singlet state of the C . Both the CS and CR rates for the metaisomer are much slower than those for the other porphyrin-linked C . Linkage dependence of the electron transfer (ET) rates can be explained by superexchange mechanism via spacer. These results demonstrate that C is a new promising building block as an acceptor in artificial photosynthetic models. 60 60 60 60 60 60 60

DOI： 10.1021/ja9628415

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Synthesis and self-assembly of porphyrin-linked fullerene on gold surface using S-Au linkage Reviewed

Akiyama T., Imahori H., Ajawakom A., Sakata Y.

Chemistry Letters ( 10 ) 907 - 908 1996.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters

Porphyrin-linked fullerene bearing methylthio group was prepared by 1,3-dipolar cycloadditon of the azomethine ylide, generated in situ using N-methylglycine and a formylporphyrin, with C . Self-assembled monolayer was formed by soaking Au electrode into a solution of the porphyrin-C dyad. The photocurrent was observed for the photochemical cell in the presence of electron carrier under illumination. 60 60

DOI： 10.1246/cl.1996.907

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Papers - AKIYAMA Tsuyoshi