Akihiko Fujiwara

Japan Synchrotron Radiation Research Institute (JASRI), Tatsuno, Hyōgo, Japan

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Publications (143)479.6 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: We report the structural design and control of electronic states of a new series of ultrafine metal-organic right square prism-shaped nanowires. These nanowires have a very small inner diameter of about 2.0 Å, which is larger than hydrogen and similar to xenon atomic diameters. The electronic states of nanowires can be widely controlled by substitution of structural components. Moreover, the platinum homometallic nanowire shows a 100 times higher proton conductivity than a palladium/platinum heterometallic one depending on the electronic states.
    No preview · Article · Apr 2016 · Angewandte Chemie International Edition
  • [Show abstract] [Hide abstract] ABSTRACT: We describe the synthesis and sorption properties of a new metal–organic framework (MOF), Fe(H2O)2(bpy)[Pt(CN)4]●H2O (bpy = 4,4’-bipyridine), with a three-dimensional accordion-like structure. Whereas all crystalline oriented MOF thin films reported to date have been limited to a layer-type structure, here we succeeded in fabricating its crystalline oriented thin film.
    No preview · Article · Apr 2016 · Chemical Communications
  • No preview · Article · Apr 2016
  • [Show abstract] [Hide abstract] ABSTRACT: The superconducting transition temperature Tc of ammoniated metal-doped FeSe (NH3)yMxFeSe (M: metal atom) has been scaled with the FeSe plane spacing, and it has been suggested that the FeSe plane spacing depends on the location of metal atoms in (NH3)yMxFeSe crystals. Although the crystal structure of (NH3)yLixFeSe exhibiting a high Tc (∼44 K) was determined from neutron diffraction, the structure of (NH3)yMxFeSe exhibiting a low Tc (∼32 K) has not been determined thus far. Here, we determined the crystal structure of (NH3)yCs0.4FeSe(Tc=33K) through the Rietveld refinement of the x-ray diffraction (XRD) pattern measured with synchrotron radiation at 30 K. The XRD pattern was analyzed based on two different models, on-center and off-center, under a space group of I4/mmm. In the on-center structure, the Cs occupies the 2a site and the N of NH3 may occupy either the 4c or 2b site, or both. In the off-center structure, the Cs may occupy either the 4c or 2b site, or both, while the N occupies the 2a site. Only an on-center structure model in which the Cs occupies the 2a and the N of NH3 occupies the 4c site provided reasonable results in the Rietveld analysis. Consequently, we concluded that (NH3)yCs0.4FeSe can be assigned to the on-center structure, which produces a smaller FeSe plane spacing leading to the lower Tc.
    No preview · Article · Mar 2016
  • No preview · Article · Mar 2016 · Nature Chemistry
  • [Show abstract] [Hide abstract] ABSTRACT: One-dimensional (1D) electronic systems have attracted significant attention for a long time because of their various physical properties. Among 1D electronic systems, 1D halogen-bridged mixed-valence transition-metal complexes (the so-called MX chains) have been thoroughly studied owing to designable structures and electronic states. Here, we report the syntheses, structures, and electronic properties of three kinds of novel neutral MX-chain complexes. The crystal structures consist of 1D chains of Pt-X repeating units with (1R,2R)-(-)-diaminocychlohexane and CN(-) in-plane ligands. Because of the absence of a counteranion, the neutral MX chains have short interchain distances, so that strong interchain electronic interaction is expected. Resonance Raman spectra and diffuse-reflectance UV-vis spectra indicate that their electronic states are mixed-valence states (charge-density-wave state: Pt(2+)···X-Pt(4+)-X···Pt(2+)···X-Pt(4+)-X···). In addition, the relationship between the intervalence charge-transfer (IVCT) band gap and the degree of distortion of the 1D chain shows that the neutral MX chains have a larger IVCT band gap than that of cationic MX-chain complexes. These results provide new insight into the physical and electronic properties of 1D chain compounds.
    No preview · Article · Feb 2016 · Inorganic Chemistry
  • [Show abstract] [Hide abstract] ABSTRACT: Highly oriented crystalline thin films of metal-organic frameworks (MOFs) have promising practical applications, such as in gas separation, catalysis, and sensing. We report on the successful fabrication of highly oriented crystalline thin films of three-dimensional porous MOFs, Fe(pz)[M(CN)4] (M = Ni, Pd; pz = pyrazine). Synchrotron X-ray diffraction studies reveal not only the highly oriented crystalline nature but also the remarkable shrunken structure of the thin films (∼3-7% volume shrinkage) compared with bulk samples. Furthermore, because of lattice shrinkage, these films exhibit large lattice expansions upon guest adsorption, in marked contrast to the almost unchanged lattice in the bulk samples.
    No preview · Article · Dec 2015 · Inorganic Chemistry
  • [Show abstract] [Hide abstract] ABSTRACT: Images of the spatial distribution of nanostructures in thin films were successfully reconstructed by grazing-incidence small-angle X-ray scattering (GISAXS) coupled with computed tomography (CT) measurements. As a model sample of inhomogeneous thin films, a thin film was patterned with four characters (F, B, S and L) consisting of nanoparticles of gold (Au), platinum (Pt), Au/Pt and Pt/Au, respectively, on a silicon substrate. The characters each produced respective two-dimensional GISAXS images which reflect the nanoparticle structures and their correlations in the thin film. The application of the GISAXS-CT technique to the characteristic scattering GISAXS intensity of each component enables one to reconstruct the images of each character independently. Moreover, it was found that the patterned images could be reconstructed even from very weak scattered intensities at higher q positions and the diffuse intensities. These results indicate that the GISAXS-CT method is a powerful tool to obtain distinct reconstruction images detailing the particle size, shape and surface roughness.
    No preview · Article · Dec 2015 · Journal of Applied Crystallography
  • [Show abstract] [Hide abstract] ABSTRACT: Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼104 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si-O-Si angles bridging rigid SiO4 tetrahedra, which efficiently transduce electric energy into elastic energy.
    No preview · Article · Nov 2015 · Applied Physics Letters
  • [Show abstract] [Hide abstract] ABSTRACT: We present the first report of a compact, planar and low-energy-gap molecule based on a π-conjugated bimetal system comprising a tetrathiooxalate () skeleton. The observed low HOMO-LUMO energy gap (1.19 eV) is attributed to its donor-acceptor-donor (D-A-D) nature because the skeleton acts as an electron acceptor as well as a tiny and noninnocent bridging moiety.
    No preview · Article · Sep 2015 · Chemical Communications
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    [Show abstract] [Hide abstract] ABSTRACT: The structure of high-temperature liquids is an important topic for understanding the fragility of liquids. Here we report the structure of a high-temperature non-glass-forming oxide liquid, ZrO2, at an atomistic and electronic level. The Bhatia–Thornton number–number structure factor of ZrO2 does not show a first sharp diffraction peak. The atomic structure comprises ZrO5, ZrO6 and ZrO7 polyhedra with a significant contribution of edge sharing of oxygen in addition to corner sharing. The variety of large oxygen coordination and polyhedral connections with short Zr–O bond lifetimes, induced by the relatively large ionic radius of zirconium, disturbs the evolution of intermediate-range ordering, which leads to a reduced electronic band gap and increased delocalization in the ionic Zr–O bonding. The details of the chemical bonding explain the extremely low viscosity of the liquid and the absence of a first sharp diffraction peak, and indicate that liquid ZrO2 is an extremely fragile liquid.
    Full-text · Article · Dec 2014 · Nature Communications
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    [Show abstract] [Hide abstract] ABSTRACT: Polymeric chain-structured complexes were prepared with helical lanthanide complexes (LnL; Ln=EuIII, TbIII, GdIII) and benzene-dicarboxylate derivatives (benzene-1,4-dicarboxylate (bdc), 2-aminoterephtalate (atpa) and 2-hydoloxyterephtalate (htpa)), which show some noteworthy physicochemical properties, photoluminescence and thermal stabilities. The complex EuL-bdc shows bright luminescence originating from EuIII by UV excitation. The emission color can be tuned by mixing with TbL. The structures of these chain complexes were clarified with synchrotron X-ray powder diffraction measurements. The derivation of the linker moiety (bdc, atpa or htpa) was found to affect the intermetal energy transfer from TbIII to EuIII.
    Full-text · Article · Nov 2014 · Polymer Journal
  • [Show abstract] [Hide abstract] ABSTRACT: The organized structure and proton transport property in sulfonated polyimide (SPI) thin film have been studied, much less is known at the interfacial charge transport during confinement of such materials. The proton conductivity of SPI thin film is correlated well with the highly oriented polymer structures as determined by infrared (IR) p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) and in situ RH dependent synchrotron grazing incidence X-ray diffraction (GI-XRD). The high proton conductivity of 2.8 × 10−1Scm−1 at 80°C and 90% RH was achieved in the highly oriented SPI thin film. In contrast, the bulk SPI showed the drop of conductivity value at high relative humidity region, which is due to the significant structural disorder accompanied by the strong interaction between the sulfonic acid side chains and water molecules.
    No preview · Article · Oct 2014 · Electrochemistry -Tokyo-
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    [Show abstract] [Hide abstract] ABSTRACT: A strategy to modulate the in-plane structural arrangement in preferentially oriented crystalline metal–organic framework (MOF) nanosheets assembled by a two-dimensional interfacial reaction between porphyrin units and metal ion linkers is reported. Starting with a tetratopic porphyrin MOF nanofilm, NAFS-2, the framework size and shape are modified by employing specially designed building units, a trans-ditopic and an expanded tetratopic porphyrin, and Cu2+ linkers. Reducing the number of binding parts affords a MOF nanosheet, NAFS-31, with a distorted in-plane structure. Extension of the peripheral substituents, while maintaining the tetratopic porphyrin geometry, results in marked unit cell size enlargement in an undistorted square grid in the MOF nanofilm, NAFS-41. The exquisite geometric control that these structural modifications entail is valuable to allow switching of chemical/physical properties of the nanosheets and lead to realization of their use in nanotechnological applications.
    Full-text · Article · Sep 2014 · ChemPlusChem
  • [Show abstract] [Hide abstract] ABSTRACT: Polymer materials have hierarchal structure in the very wide range of scale. It is well known that the property is dependent on the hierarchical structure. In order to improve the performance of the materials, clarifying the hierarchical structure in a wide range and the feed back to the manufacturing process are important. However, it is difficult to clarify the hierarchical heterogeneous structure of polymer materials using only single method. Therefore the combination of microbeam small- and wide- angle X-ray scattering (SAXS/WAXS) is useful for evaluation of the hierarchical heterogeneous structural of polymer materials. The BL03XU, in alias, FSBL, in SPring-8 was constructed by consortium of industrial and academic groups and has been used from 20101),2). Structure characterization of advanced materials in the industrial field has been carried out using microbeam SAXS/WAXS method. In addition to the description of the SAXS/WAXS measurement system at BL03XU, we will report on the local structural evaluation of carbon fiber (CF). A hierarchal heterogeneous structure of CFs was visualized in the space resolution of 1 μm using a microbeam and an X-ray imaging technique. The image contrasts were identified by the difference in peak positions corresponding to the void size, the peak width corresponding to the crystallite size, and intensities corresponding to the amount of crystallites and voids. The X-ray scattering images of high-modulus CF are shown in a figure. Nanometer-size voids estimated by SAXS are abundant in the center of a fiber, on the other hand, the crystallite is abundant in the vicinity of a surface was revealed. It is suggested that the voids were generated near the center of the fiber to relax the strain during the crystallization process from the surface during the graphitization of fibers. We succeeded in visualizing the distribution of voids and crystallite of a few nanometers, which cannot be observed by an X-ray transmission imaging method.
    No preview · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
  • Akihiko Fujiwara · Yoko Sugawara · Atsushi Nakagawa · Masaki Takata
    [Show abstract] [Hide abstract] ABSTRACT: A century ago, crystallogtaphy ushered in the era of modern science & technology in Japan. The beginning of modern crystallography in Japan dates back to 1913. Torahiko Terada (Tokyo Imperial University) demonstrated X-ray diffraction[1] and Shoji Nishikawa (Tokyo Imperial University) reported on X-ray patterns of fibrous, lamellar and granular substances[2]. In 1936, Ukichiro Nakaya (Hokkaido University) successfully classified natural snow crystals and made the first artificial snow crystals. In the last half-century, developments in crystallography helped form thriving manufacturing sectors such as the semiconductor industry, the iron and steel industries, the pharmaceutical industry, the electronics industry, the textile industry, and the polymer industry, as well as a wide array of academic research.
    No preview · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
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    [Show abstract] [Hide abstract] ABSTRACT: The conductive organic polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate), abbreviated as PEDOT:PSS, is widely used in capacitors, antistatic coating etc. and one of the potential materials for the next-generation printable electronics. It is because of its excellent dispersibility in water and high electronic conductivity of more than 1,000 S/cm. Although many preceding studies have provided a variety of possible mechanisms of high conductivity, such as charge transfer between PEDOT and residual solvents, there has been no conclusive explanation for the origin of the high conductivity. Here, we report the nanometer-size crystallization of PEDOT inside the hydrophobic core region of PEDOT:PSS in a solid film and enhancement of electronic conductivity caused by the nanometer-size crystal growth of PEDOT. The structure of PEDOT:PSS has been investigated by means of small- and wide-angle X-ray scatterings (SAXS and WAXS) using high brilliance synchrotron radiation light source in SPring-8, Japan. We have obtained the microscopic structural model of PEDOT:PSS micelle in the water dispersion and the solid polymer film (Fig. 1(a)). Nanometer-size crystals of PEDOT were grown during the course of film fabrication in the wet process from the water dispersion. Furthermore, we found that the better crystallinity of the PEDOT crystal in the films prepared in the different conditions resulted in the higher electrical conductivity (Fig. 1(b)). The result suggests that the size of the crystallite is one of the key parameters for the enhancement of the electronic conductivity in PEDOT:PSS films. These findings shed light on the further improvement of the electrical conductivity of PEDOT:PSS polymer films by controlling the evaporation to dryness in the wet fabrication process.
    Preview · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
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    [Show abstract] [Hide abstract] ABSTRACT: Highly luminescent lanthanide (Ln) complexes have attracted much attention because Ln 3 + ions show long-lived ff-emissions with narrow band shape. Their unique photo-optical properties are promising for the design of light-emitting materials and sensing devices. Although the ff-emissions are essentially weak because of Laporte forbidden, chelate ligands is effective to strengthen the intramolecular energy transfer from photo-excited organic ligands to Ln 3 + ions. The direct evidence of energy transfer from ligands to Ln 3 + and details of excited state, however, are still veiled. Here, we report direct visualization of energy-transferred excited state in Eu complex with a hexadentate ligand (L) consisting of two bipyridine moieties bridged by an ethylendiamine unit, [Eu 3 + (L)(NO 3 ) 2 ](PF 6 ) (Eu(L))[1] by Maximum Entropy Method (MEM) charge density[2] and electrostatic potential analysis[3] based on SR X-ray diffraction. First, we confirmed that the electron numbers of Eu and ligand L in the excited state are the same as those in the ground state, which is a direct evidence of energy transfer instead of charge transfer. Next, we observed charge re-distribution in the Eu ion and the ligand L. The electrostatic potential distributions calculated using MEM charge density give an experimental evidence for the existence of polarization of ligand L both in the ground and photo-excited states. The orientation polarization in the ground state changed during pumping at 315 nm, and the charge re-distribution are qualitatively consistent with a theoretical prediction. This characteristic luminescence behavior based on the energy relaxation process have not been detected by fundamental crystal structural analysis. We have succeeded in visualization of subtle but important change due to energy transfer in the mononuclear Europium complex with hexadentate ligand at the first time.
    Preview · Article · Aug 2014 · Acta Crystallographica Section A: Foundations and Advances
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    [Show abstract] [Hide abstract] ABSTRACT: Electric dipole engineering is now an emerging technology for high electron-mobility transistors, ferroelectric random access memory and multiferroic devices etc. Although various studies to provide insight into dipole moment behaviour, such as phase transition, order and disorder states, have been reported, macroscopic spontaneous polarization has been mainly discussed so far. Here, visualization of the electric dipole arrangement in layered ferro-electrics Bi 2 SiO 5 by means of combined analysis of maximum entropy charge density and electrostatic potential distribution analysis based on synchrotron radiation X-ray powder diffraction data is reported. It was found that the hierarchical dipole orders, the weak-ferroelectric and ferroelectric configura-tions, were observed in the Bi 2 O 2 and the SiO 3 layers, respectively, and the ferrielectric configuration was realised by the interlayer interaction. This discovery provides a new method to visualize the local polarization in ferroelectric materials.
    Full-text · Dataset · May 2014
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    [Show abstract] [Hide abstract] ABSTRACT: Understanding the nature of superconductivity in iron-based compounds is essential in the development of new strategies to increase T c. Using a charge density analysis based on synchrotron radiation X-ray powder diffraction data, we found that the charge carriers only accumulated in the iron layer of the superconducting phase of LaFeAsO1 − xFx at low temperatures. Analysis of the electrostatic potential distribution revealed the concerted enhancement of the electronic polarization of the As ions and the carrier redistribution. This suggests that the enhanced electronic polarization of the As ion plays an important role in inducing high T c superconductivity, and that the polaron concept, which has been previously regarded as an untenable mechanism, should be reconsidered for the description of the iron–arsenide superconducting phase.
    Full-text · Article · May 2014

Publication Stats

3k Citations
479.60 Total Impact Points

Institutions

  • 2012-2015
    • Japan Synchrotron Radiation Research Institute (JASRI)
      Tatsuno, Hyōgo, Japan
    • Tohoku University
      • Department of Physics
      Sendai-shi, Miyagi, Japan
  • 2013
    • RIKEN
      Вако, Saitama, Japan
  • 2003-2012
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 2011
    • The Electrochemical Society
      Society Hill, New Jersey, United States
  • 2002-2010
    • Japan Advanced Institute of Science and Technology
      • School of Materials Science
      KMQ, Ishikawa, Japan
  • 1998-2002
    • The University of Tokyo
      • Department of Physics
      Tokyo, Tokyo-to, Japan
  • 2000
    • Tokyo Metropolitan University
      • Department of Physics
      Edo, Tokyo, Japan