Hisaaki Tanaka

Publications (24)130.79 Total impact

• Source

  Available from: Maria Laura Mercuri

  Article: New BDH-TTP/[M(III)(C(5)O(5))(3)](3-) (M = Fe, Ga) Isostructural Molecular Metals.

  Luca Pilia, Elisa Sessini, Flavia Artizzu, Masahiro Yamashita, Angela Serpe, Kazuya Kubo, Hiroshi Ito, Hisaaki Tanaka, Shin-Ichi Kuroda, Jun-Ichi Yamada, Paola Deplano, Carlos J Gómez-García, Maria Laura Mercuri
  [show abstract] [hide abstract]
  ABSTRACT: Two new isostructural molecular metals-(BDH-TTP)(6)[M(III)(C(5)O(5))(3)]·CH(2)Cl(2) (BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, where M = Fe (1) and Ga (2))-have been prepared and fully characterized. Compound 1 is a molecular conductor showing paramagnetic behavior, which is due to the presence of isolated [Fe(C(5)O(5))(3)](3-) complexes with high-spin S = (5)/(2) Fe(III) metal ions. The conductivity originates from the BDH-TTP organic donors arranged in a κ-type molecular packing. At 4 kbar, compound 1 behaves as a metal down to ∼100 K, showing high conductivity (∼10 S cm(-1)) at room temperature. When applying a pressure higher than 7 kbar, the metal-insulator (M-I) transition is suppressed and the compound retains the metallic state down to low temperatures (2 K). For 1, ESR signals have been interpreted as being caused by the fine structure splitting of the high-spin (S = (5)/(2)) state of Fe(III) in the distorted octahedral crystal field from the ligands. At 4 kbar, the isostructural compound 2 behaves as a metal down to ∼100 K, although it is noteworthy that the M-I transition is not suppressed, even at pressures of 15 kbar. For 2, only the signal assigned to delocalized π-electrons has been observed in the ESR measurements.
  Inorganic Chemistry 12/2012; · 4.60 Impact Factor
• Article: Microscopic mechanisms behind the high mobility in rubrene single-crystal transistors as revealed by field-induced electron spin resonance

  Kazuhiro Marumoto, Norimichi Arai, Hiromasa Goto, Masashi Kijima, Kouichi Murakami, Yukihiro Tominari, Jun Takeya, Yukihiro Shimoi, Hisaaki Tanaka, Shin-ichi Kuroda, Toshihiko Kaji, Takao Nishikawa, Taishi Takenobu, Yoshihiro Iwasa
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  ABSTRACT: The microscopic mechanisms behind the very high mobility in rubrene single-crystal transistors achieved by interface treatments with self-assembled monolayers (SAMs) have been clarified by using field-induced electron spin resonance (FI-ESR). Clearly observed FI-ESR signals exhibit extremely narrow linewidths owing to the very high carrier mobility. The precise angular dependence of FI-ESR g values shows that crystallinity in the semiconductor channel is unchanged by the SAM treatments. The trapping time of charge carriers at the interface directly evaluated from the ESR linewidth greatly decreases from ∼700 to ∼60 ps concomitant with the remarkable improvement in mobility because of the SAM treatments.
  Phys. Rev. B. 02/2011; 83(7).
• Source

  Available from: 144.206.159.178

  Article: Electron spin resonance observation of field-induced charge carriers in ultrathin-film transistors of regioregular poly(3-hexylthiophene) with controlled in-plane chain orientation

  Shun-ichiro Watanabe, Hisaaki Tanaka, Shin-ichi Kuroda, Akio Toda, Shusaku Nagano, Takahiro Seki, Atsushi Kimoto, Jiro Abe
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  ABSTRACT: Ultrathin-film polymeric transistors with controlled in-plane chain orientation have been fabricated based on Langmuir–Blodgett technique by cospreading liquid crystal molecule with regioregular poly(3-hexylthiophene). The mobilities parallel to the chain direction reached 0.001–0.01 cm2/V s for 1 to 5 monolayer thick transistors. Mobility ratio was about 2 for the parallel and perpendicular directions. Electron spin resonance (ESR) signals of the field-induced polarons exhibited clear in-plane anisotropies due to unpaired π-electrons. The anisotropic ESR spectra together with the optical dichroism determine the detailed molecular orientations in the channel of such ultrathin transistors.
  Applied Physics Letters 04/2010; 96(17):173302-173302-3. · 3.84 Impact Factor
• Article: Water-vapor-induced reversible switching of electronic states in an MMX-type chain complex with retention of single crystallinity.

  Hiroaki Iguchi, Shinya Takaishi, Hitoshi Miyasaka, Masahiro Yamashita, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Shin-Ichi Kuroda
  Angewandte Chemie International Edition 12/2009; 49(3):552-5. · 13.45 Impact Factor
• Article: Effect of an in-plane ligand on the electronic structures of bromo-bridged nano-wire Ni-Pd mixed-metal complexes, [Ni(1-x)Pd(x)(bn)2Br]Br2 (bn = 2S,3S-diaminobutane).

  Mari Sasaki, Hashen Wu, Daisuke Kawakami, Shinya Takaishi, Takashi Kajiwara, Hitoshi Miyasaka, Brian K Breedlove, Masahiro Yamashita, Hideo Kishida, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Shinichi Kuroda
  [show abstract] [hide abstract]
  ABSTRACT: Single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal complexes with 2S,3S-diaminobutane (bn) as an in-plane ligand, [Ni(1-x)Pd(x)(bn)(2)Br]Br(2), were obtained by using an electrochemical oxidation method involving mixed methanol/2-propanol (1:1) solutions containing different ratios of [Ni(II)(bn)(2)]Br(2) and [Pd(II)(bn)(2)]Br(2). To investigate the competition between the electron-correlation of the Ni(III) states, or Mott-Hubbard states (MH), and the electron-phonon interaction of the Pd(II)-Pd(IV) mixed valence states, or charge-density-wave states (CDW), in the Ni-Pd mixed-metal compounds, X-ray structure analyses, X-ray oscillation photograph, and Raman, IR, ESR, and single-crystal reflectance spectra were analyzed. In addition, the local electronic structures of Ni-Pd mixed-metal single crystals were directly investigated by using scanning tunneling microscopy (STM) at room temperature and ambient pressure. The oxidation states of [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) changed from a M(II)-M(IV) mixed valence state to a M(III) MH state at a critical mixing ratio (x(c)) of approximately 0.8, which is lower than that of [Ni(1-x)Pd(x)(chxn)(2)Br]Br(2) (chxn = 1R,2R-diaminocyclohexane) (x(c) approximately 0.9) reported previously. The lower value of x(c) for [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) can be explained by the difference in their CDW dimensionalities because the three-dimensional CDW ordering in [Pd(bn)(2)Br]Br(2) observed by using X-ray diffuse scattering stabilizes the Pd(II)-Pd(IV) mixed valence state more than two-dimensional CDW ordering in [Pd(chxn)(2)Br]Br(2) does, which has been reported previously.
  Inorganic Chemistry 08/2009; 48(15):7446-51. · 4.60 Impact Factor
• Article: Direct observation of the charge carrier concentration in organic field-effect transistors by electron spin resonance

  Hisaaki Tanaka, Shun-ichiro Watanabe, Hiroshi Ito, Kazuhiro Marumoto, Shin-ichi Kuroda
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  ABSTRACT: Charge carrier concentration in operating field-effect transistor (FET) of regioregular poly(3-hexylthiophene) has been directly determined by electron spin resonance (ESR). ESR signals of field-induced polarons are observed around g=2.003 under the application of negative gate-source voltage (V_gs) . Upon applying drain-source voltage (V_ds) , ESR intensity decreases linearly in the low V_ds region, reaching to about 50% of the initial intensity at the pinch-off point (V_ds≅V_gs) . For larger absolute values of V_ds , it becomes nearly V_ds independent. These behaviors are well explained by the change in the carrier concentration obtained by the FET theory using gradual channel approximation.
  Applied Physics Letters 04/2009; · 3.84 Impact Factor
• Article: Uniaxial compression on the superconductivity of β-BDA-TTP salts

  Hiroshi Ito, Tetsuo Ishihara, Hisaaki Tanaka, Shin-ichi Kuroda, Jun-ichi Yamada
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  ABSTRACT: The β-type BDA-TTP superconductors attract attention due to the high transition temperature Tc at ambient pressure for organic superconductors. In order to get insight into the superconductivity in terms of the dimerized anisotropic triangular lattice model, Tc of β-(BDA-TTP)2X [X = SbF6, X = AsF6] is studied under uniaxial compression by resistivity measurements. Under compression parallel to the donor stack, Tc increases gradually up to 3 (X = SbF6), 5 (X = AsF6) kbar, and decreases under further piston pressure. Under compression perpendicular to the donor stack, Tc decreases gradually up to 2.5 (X = SbF6), 4 (X = AsF6) kbar and then decreases rapidly under further pressure. Only for X = AsF6, a Tc minimum at 3 kbar is found for both direction. These trends in Tc are understood as an interplay between the enhancement of antiferromagnetic spin fluctuation and frustration on the triangular lattice. By the interplane compression, Tc increased by 0.5 K up to 2 kbar for both salts, demonstrating the importance of the interlayer interaction.
  Journal of Physics Conference Series 10/2008; 132(1):012012.
• Article: Charge-density-wave to Mott-Hubbard phase transition in quasi-one-dimensional bromo-bridged Pd compounds.

  Shinya Takaishi, Mitsuhito Takamura, Takashi Kajiwara, Hitoshi Miyasaka, Masahiro Yamashita, Muneaki Iwata, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Shin-ichi Kuroda, Hiroyuki Nishikawa, Hiroki Oshio, Kenichi Kato, Masaki Takata
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  ABSTRACT: A -Pd(III)-Br-Pd(III)-Mott-Hubbard state was observed in a quasi-one-dimensional bromo-bridged Pd compound [Pd(en)2Br](C5-Y)2 x H2O (en = ethylenediamine, C5-Y = dipentylsulfosuccinate) for the first time. The phase transition between Mott-Hubbard and charge-density-wave states occurred at 206 +/- 2 K and was confirmed by using X-ray, ESR, Raman and electronic spectroscopies, electrical resistivity, and heat capacity. From X-ray powder diffraction patterns and Raman spectra of a series of Pd-Br compounds, [Pd(en)2Br](C(n)-Y)2 x H2O (n = 4, 5, 6, 7, 8, 9, and 12), chemical pressure from the alkyl chains of the counterions caused the phase transition.
  Journal of the American Chemical Society 10/2008; 130(36):12080-4. · 9.91 Impact Factor
• Article: ESR observation of optically generated solitons in the quasi-one-dimensional iodo-bridged diplatinum complex Pt_ {2}(n-pentylCS_ {2}) _ {4} I

  Hisaaki Tanaka, Hideshi Nishiyama, Shin-ichi Kuroda, Takami Yamashita, Minoru Mitsumi, Koshiro Toriumi
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  ABSTRACT: Light-induced electron spin resonance (LESR) measurements have been performed on a quasi-one-dimensional (Q1D) iodo-bridged diplatinum complex Pt2(n-pentylCS2)4I, where the thermal activation of solitons has been reported in the doubly-degenerate alternate-charge-polarization (ACP) [Pt2+-Pt3+-I−-Pt3+-Pt2+] state formed below 210 K. An enhancement of ESR signal has been detected due to the photogeneration of Pt3+ spins below about 30 K, as confirmed through the observed g values of g∥=1.980 and g⊥=2.215 with the external field parallel and perpendicular to the chain axis, respectively. The LESR linewidth is clearly smaller than that of the ESR signal of Curie spins observed under the dark condition, whereas it exhibits uniaxial anisotropy similar to that of the dark ESR due to the anisotropic hyperfine interaction of Pt and iodine nuclear spins. The small LESR linewidth compares well with the motionally-narrowed ESR linewidth of thermally activated solitons at elevated temperatures, indicating that the photogenerated spins are mobile. Furthermore, bimolecular recombination of photogenerated spins has been demonstrated from the excitation power dependence and decay curves of LESR intensity. These LESR features strongly suggest that the mobile spins are photogenerated solitons, which agrees with theoretical predictions.
  Phys. Rev. B. 07/2008; 78(3).
• Article: Electronic structure of Co(III) doped bromo-bridged Ni complexes, [Ni1-xCox(chxn)2Br]Br2.

  Jimin Xie, Hashen Wu, Daisuke Kawakami, Hiroaki Iguchi, Shinya Takaishi, Masahiro Yamashita, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Shin-ichi Kuroda
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  ABSTRACT: This article describes the electronic structure of the Co(III) doped Br bridged Ni(III) complexes, [Ni(1-x)Cox(chxn)2Br]Br2 (x = 0.01, 0.02, 0.05, and 0.11) by using a optical spectroscopy, scanning tunneling microscopy (STM), and electron spin resonance spectroscopy. In the optical reflectivity spectrum, the new band was formed at about 0.5 eV, which is reasonably recognized as the d(z2) band of doped Co(III) ions. In the STM images of [Ni(1-x)Cox(chxn)2Br]Br2, the bright spots attributable to the tunnel current from the Fermi level of the STM tip to the conduction band of the sample were observed. In addition, some brighter spots were also observed. Because the number of the brighter spots is in good agreement with that of doped Co species, the brighter spots can be assigned to doped Co(III) sites. These are reasonably explained by the tunnel current from the Fermi level of the tip to the d(z2) band of Co(III). The Curie spin concentration was gradually increased with increasing Co(III) ions, which is explained by the scissions of the S = 1/2 1D antiferromagnetic chains.
  Inorganic Chemistry 04/2008; 47(6):1949-52. · 4.60 Impact Factor
• Article: One-dimensional bromo-bridged Ni III complexes [Ni(S,S-bn)2Br]Br2 (S,S-bn=2S,3S-diaminobutane): synthesis, physical properties, and electrostatic carrier doping.

  Shinya Takaishi, Masahiro Yamashita, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Shin-ichi Kuroda, Atsushi Goto, Tadashi Shimizu, Taishi Takenobu, Yoshihiro Iwasa
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  ABSTRACT: A new bromo-bridged Ni III compound has been synthesized. This compound displayed a strong antiferromagnetic interaction between spins located on Ni III species (J=(2350+/-500) K) that result from the strong covalency of the Ni--Br bond and the spin-Peierls transition below 150 K. This was shown by the results of magnetic susceptibility and 81Br nuclear quadrupole resonance spectroscopy analysis. We succeeded in the electrostatic carrier doping of a single crystalline sample by using a field-effect transistor device. This compound also showed n-type semiconductor behavior, which can be reasonably rationalized by the existence of a small amount of Ni II impurities.
  Chemistry 02/2008; 14(2):472-7. · 5.93 Impact Factor
• Article: Lineage-specific dependency of lung adenocarcinomas on the lung development regulator TTF-1.

  Hisaaki Tanaka, Kiyoshi Yanagisawa, Keiko Shinjo, Ayumu Taguchi, Ken Maeno, Shuta Tomida, Yukako Shimada, Hirotaka Osada, Takayuki Kosaka, Hideo Matsubara, Tetsuya Mitsudomi, Yoshitaka Sekido, Mitsune Tanimoto, Yasushi Yatabe, Takashi Takahashi
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  ABSTRACT: Emerging evidence, although currently very sparse, suggests the presence of "lineage-specific dependency" in the survival mechanisms of certain cancers. TTF-1 has a decisive role as a master regulatory transcription factor in lung development and in the maintenance of the functions of terminal respiratory unit (TRU) cells. We show that a subset of lung adenocarcinoma cell lines expressing TTF-1, which presumably represent those derived from the TRU lineage, exhibit marked dependence on the persistent expression of TTF-1. The inhibition of TTF-1 by RNA interference (RNAi) significantly and specifically induced growth inhibition and apoptosis in these adenocarcinoma cell lines. Furthermore, a fraction of TTF-1-expressing tumors and cell lines displayed an increase in the gene dosage of TTF-1 in the analysis of 214 patients with non-small-cell lung cancer, including 174 adenocarcinomas, showing a tendency of higher frequency of increased gene copies at metastatic sites than at primary sites (P=0.07, by two-sided Fisher's exact test). These findings strongly suggest that in addition to the development and maintenance of TRU lineages in normal lung, sustained TTF-1 expression may be crucial for the survival of a subset of adenocarcinomas that express TTF-1, providing credence for the lineage-specific dependency model.
  Cancer Research 08/2007; 67(13):6007-11. · 7.86 Impact Factor
• Article: Metal-insulator transition of charge-transfer salts based on unsymmetrical donor DMET and metal halide anions (DMET)4(MCl4)(TCE)2 (M = Mn, Co, Cu, Zn; TCE = 1,1,2-trichloroethane).

  Hiroshi Ito, Daichi Suzuki, Harutaka Watanabe, Hisaaki Tanaka, Shin-ichi Kuroda, Masamichi Umemiya, Norihito Kobayashi, Makoto Goto, Ken-ichi Sugiura, Hitoshi Miyasaka, Shinya Takaishi, Takashi Kajiwara, Masahiro Yamashita, Eiji Ohmichi, Toshihito Osada
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  ABSTRACT: New charge-transfer salts based on an unsymmetrical donor DMET [dimethyl(ethylenedithio)diselenadithiafulvalene] and metal halide anions (DMET)4MIICl4(TCE)2 (M = Mn, Co, Cu, Zn; TCE = 1,1,2-trichloroethane) have been synthesized and characterized by transport and magnetic measurements. The crystal structures of the DMET salts are isostructural, consisting of a quasi-one-dimensional stack of DMET and insulating layers containing metal halide anions and TCE. Semimetallic band structures are calculated by the tight-binding approximation. Metal-insulator transitions are observed at TMI = 25, 15, 5-20, and 13 K for M = Mn, Co, Cu, and Zn, respectively. The M = Cu salt exhibits anisotropic conduction at ambient pressure, being semiconducting in the intralayer current direction but metallic for the interplane current direction, down to T(MI). The metal-insulator transitions are suppressed under pressure. In the M = Co and Zn salts, large magnetoresistances with hysteresis are observed at low temperatures, on which Shubnikov-de Haas oscillations are superposed above 30 T. In the M = Cu salt, no hysteresis is observed but clear Shubnikov-de Haas oscillations are observed. The magnetoresistance is small and monotonic in the M = Mn salt. Paramagnetic susceptibilities of the spins of the magnetic ions are observed for the M = Mn, Co, and Cu salts with small negative Weiss temperatures of approximately 1 K. In the nonmagnetic M = Zn salt, Pauli-like pi-electron susceptibility that vanishes at TMI is observed. The ground state of the pi-electron system is understood as being a spin density wave state caused by imperfect nesting of the Fermi surfaces. In this pi-electron system, the magnetic ions of the M = Mn, Co, and Cu salts interact differently, exhibiting a variety of transport behaviors.
  Journal of the American Chemical Society 08/2007; 129(27):8510-8. · 9.91 Impact Factor
• Article: Dynamical valence fluctuation at the charge-density-wave phase boundary in iodide-bridged Pt compound [Pt(chxn)2I]I2.

  Shinya Takaishi, Daisuke Kawakami, Masahiro Yamashita, Mari Sasaki, Takashi Kajiwara, Hitoshi Miyasaka, Ken-Ichi Sugiura, Yusuke Wakabayashi, Hiroshi Sawa, Hiroyuki Matsuzaki, Hideo Kishida, Hiroshi Okamoto, Harutaka Watanabe, Hisaaki Tanaka, Kazuhiro Marumoto, Hiroshi Ito, Shin-Ichi Kuroda
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  ABSTRACT: We synthesized a novel iodo-bridged linear chain platinum compound, having the quasi-two-dimensional charge-density-wave (CDW) ground state and the smallest band gap. In this compound, we discovered an anomalous valence state in the boundary region at which the CDW phase alternates in the crystal by means of ESR, X-ray diffuse scattering, STM, and electrical resistivity. This anomalous state can be explained by the fast fluctuation between Pt(IV)-I...Pt(II) and Pt(II)...I-Pt(IV) in the double well potential. This is the first observation of the dynamical fluctuation of the CDW phase among the quasi one-dimensional halogen-bridged complexes.
  Journal of the American Chemical Society 06/2006; 128(19):6420-5. · 9.91 Impact Factor
• Article: A neutral mixed-valent conducting polymer formed by electron transfer between metal d and ligand pi orbitals.

  Minoru Mitsumi, Hidekazu Goto, Shunsuke Umebayashi, Yoshiki Ozawa, Mototada Kobayashi, Toshihiko Yokoyama, Hisaaki Tanaka, Shin-ichi Kuroda, Koshiro Toriumi
  Angewandte Chemie International Edition 08/2005; 44(27):4164-8. · 13.45 Impact Factor
• Article: Reduced expression of Dicer associated with poor prognosis in lung cancer patients.

  Yoko Karube, Hisaaki Tanaka, Hirotaka Osada, Shuta Tomida, Yoshio Tatematsu, Kiyoshi Yanagisawa, Yasushi Yatabe, Junichi Takamizawa, Shinichiro Miyoshi, Tetsuya Mitsudomi, Takashi Takahashi
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  ABSTRACT: Emerging evidence suggests that microRNA, which are well-conserved, abundant and small regulatory RNA, may be involved in the pathogenesis of human cancers. We recently reported that expression of let-7 was frequently reduced in lung cancers, and that reduced let-7 expression was significantly associated with shorter patient survival. Two members of the double-stranded RNA-specific endonuclease family, Dicer and Drosha, convert precursor forms of microRNA into their mature forms using a stepwise process. In the present study, we examined expression levels of these genes in 67 non-small cell lung cancer cases, and found for the first time that Dicer expression levels were reduced in a fraction of lung cancers with a significant prognostic impact on the survival of surgically treated cases. It should be noted that multivariate COX regression analysis showed that the prognostic impact of Dicer (P=0.001) appears to be independent of disease stage (P=0.001), while logistic regression analysis demonstrated that the higher incidence of reduced Dicer expression in poorly differentiated tumors remained significant even after correction for other parameters (P=0.02). Given the fundamental and multiple biological roles of Dicer in various cellular processes, our results suggest the involvement of reduced Dicer expression in the development of lung cancers, thus warranting further investigations of the underlying mechanisms, which can be expected to enhance understanding of the molecular pathogenesis of this fatal cancer.
  Cancer Science 03/2005; 96(2):111-5. · 3.33 Impact Factor
• Article: [[[Pt(en)2][PtX2(en)2]]3][[(MX5)X3]2].12 H2O: quasi-one-dimensional halogen-bridged PtII-PtIV mixed-valence compounds with magnetic counteranions.

  Masahiro Yamashita, Daisuke Kawakami, Satoshi Matsunaga, Yoshio Nakayama, Mari Sasaki, Shinya Takaishi, Fumiyasu Iwahori, Hitoshi Miyasaka, Ken-ichi Sugiura, Yoshiki Wada, Hiroshi Miyamae, Hiroyuki Matsuzaki, Hiroshi Okamoto, Hisaaki Tanaka, Kazuhiro Marumoto, Shin-ichi Kuroda
  Angewandte Chemie International Edition 10/2004; 43(36):4763-7. · 13.45 Impact Factor
• Article: Visualization of local valence structures in quasi-one-dimensional halogen-bridged complexes [Ni(1-x)Pd(x)(chxn)(2)Br]Br(2) by STM.

  Shinya Takaishi, Hitoshi Miyasaka, Ken-ichi Sugiura, Masahiro Yamashita, Hiroyuki Matsuzaki, Hideo Kishida, Hiroshi Okamoto, Hisaaki Tanaka, Kazuhiro Marumoto, Hiroshi Ito, Shin-ichi Kuroda, Tomohide Takami
  Angewandte Chemie International Edition 07/2004; 43(24):3171-5. · 13.45 Impact Factor
• Source

  Available from: nju.edu.cn

  Article: Carrier doping effect into quasi-one-dimensional bromo-bridged Ni(III) complexes with strong electron-correlation by Cu(II) ions, [Ni1-xCux(chxn)2Br]Br2-x.

  Masahiro Yamashita, Takashi Ono, Satoshi Matsunaga, Mari Sasaki, Shinya Takaishi, Fumiyasu Iwahori, Hitoshi Miyasaka, Ken-ihi Sugiura, Hideo Kishida, Hiroshi Okamoto, Hisaaki Tanaka, Yasuhisa Hasegawa, Kazuhiro Marumoto, Hiroshi Ito, Sin-Ichi Kuroda, Noriyoshi Kimura
  [show abstract] [hide abstract]
  ABSTRACT: This communication will describe the electron doping effect into Ni(III) complexes by Cu(II) ions, [Ni(1-x)Cu(x)(chxn)(2)Br]Br(2-x) (x = 0.038 and 0.101) by using an electrochemical oxidation method. A drastic increase of electrical conductivity as well as a new absorption band around 0.5 eV in single crystal reflectance spectra was observed by doping Cu(II) ions, indicating the electron doping was successfully made. An ESR result shows unpaired electrons locate in the d(x2-y2) orbitals of Cu(II) and have almost no interaction with those of other ions.
  Inorganic Chemistry 01/2004; 42(24):7692-4. · 4.60 Impact Factor
• Article: Direct determination of interfacial molecular orientations in field-effect devices of P3HT/PCBM composites by electron spin resonance

  Shun-ichiro Watanabe, Hisaaki Tanaka, Hiroshi Ito, Shin-ichi Kuroda, Tatsuo Mori, Kazuhiro Marumoto, Yukihiro Shimoi
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  ABSTRACT: Field-induced electron spin resonance (FI-ESR) measurements have been performed on metal–insulator-semiconductor diode structures using regioregular poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) composites with various mixing ratios on a parylene gate insulator. For lower PCBM mixing ratios, clear FI-ESR signals of hole carriers were observed around g = 2.0031, with the external magnetic field normal to the substrate plane, indicating the edge-on orientation of P3HT lamellar structures at the device interface. On the other hand, for higher PCBM mixing ratios above 50 wt.%, a new additional peak was observed at g = 2.0022, which is characteristic of the pπ-orbital axis, indicating the occurrence of flat-on P3HT domains. Ambipolar charge transport was also observed in field-effect transistors using P3HT/PCBM on parylene. With increasing PCBM fraction, from 0 to 100 wt.%, the field-effect mobility of holes decreased from 10−3 to 10−6 cm2/Vs, while that of electrons increased from 10−5 to 10−2 cm2/Vs. These results demonstrate that the flat-on orientation strongly reduces the charge carrier transport for holes because two-dimensional charge transport assisted by π–π interaction is interrupted by the presence of the flat-on structures.Graphical abstractField-induced ESR is a powerful tool to investigate the interfacial molecular orientations for P3HT domains in field-effect devices of P3HT/PCBM composites. As increasing PCBM mixing fractions, the unique co-existence of both edge- and flat-on domains was directly determined by g-value anisotropy and simulating the split ESR signals. The demonstrated flat-on domains strongly reduce the field-effect mobility for holes.Research highlights► Field-induced ESR directly determines interfacial molecular orientations of P3HT. ► Introduced PCBM modulates the original edge-on orientation partly into a flat-on one. ► Co-existence of both edge- and flat-on orientations depends on PCBM mixing fractions. ► Flat-on orientations strongly reduce the field-effect mobility of holes.
  Organic Electronics 12(4):716-723. · 4.05 Impact Factor