Akihiko Fujiwara

Kwansei Gakuin University, Nishinomiya, Hyōgo, Japan

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Publications (134)431.42 Total impact

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    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
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    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
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    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
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    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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    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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    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
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    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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    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
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    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
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    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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    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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    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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    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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    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
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    ABSTRACT: We have developed anomalous x-ray scattering (AXS) spectrometers, that employ intrinsic Ge detectors and crystal analyzers, at SPring-8. The use of LiF analyzer crystal provides us with an energy resolution of ~ 12 eV. Furthermore, it has been established that the use of AXS technique is essential to reveal the relationship between the atomic structure and its function of a fast phase-change material, Ge2Sb2Te5. We were able to address the issue of why the amorphous phase of fast phase change materials is stable at room temperature for a long time despite the fact that it can rapidly transform to the crystalline phase by using a combination of AXS and large scale density functional theory-based molecular dynamics simulations.
    Full-text · Article · Apr 2014 · Journal of Physics Conference Series
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    ABSTRACT: Single-crystal X-ray diffraction was employed to study the structural-electronic phase transition of IrTe$_2$ at approximately 270 K. The low-temperature structure was found to be a triclinic (space group $P\bar{1}$) characterized by the partial formation of Ir$_2$ dimers in the triangular lattice of IrTe$_2$, resulting in a structural modulation with a wave vector of ${\bf q} = (1/5, 0, -1/5)$. First-principles band calculations demonstrate that tilted two-dimensional Fermi surfaces emerge in the triclinic phase, suggesting that switching of the conducting planes occurs from the basal plane of the trigonal IrTe$_2$ to the tilted plane normal to ${\bf q}$ of the triclinic IrTe$_2$.
    Preview · Article · Feb 2014 · Journal of the Physical Society of Japan
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    ABSTRACT: Ladder systems situated in a crossover from one dimensionality to two dimensionalities have been an attractive research target, because the physical properties, which are associated with dimensionality, are strongly dependent on the number of constituent legs. However, control of the intraladder configuration and electronic properties based on the substitution of structural components remain challenging tasks in materials science. On the other hand, structural design using coordination chemistry offers crucial advantages for architectural and electronic variations through substitutions of metal-organic building blocks. Here, we show the rational design and electronic properties of novel metal complex-based two-legged ladder compounds with several organic rung units: 4,4'-bipyridine, trans-1,4-diaminocyclohexane, and 4,4'-azopyridine. Single-crystal X-ray studies show that these two-legged ladder compounds are composed of halogen-bridged mixed-valence one-dimensional chains (MX chains) as their constituent legs. Depending on the molecular shape of the organic rung units, unique configurations of two-legged ladder lattices with periodic distortion of the legs are achieved. In addition, the electronic absorption spectra show that intervalence charge-transfer (IVCT) band gap of the two-legged ladder system increases with increasing degree of distortion of the leg. We have demonstrated for the first time that a two-legged ladder system shows a unique relationship between IVCT energy and the distortion parameter of the leg, as distinct from a single MX chain system. These systematic investigations, not only of configurations based on the rung variation but also of electronic states in metal-organic ladder system, provide the possibility for wide and rational tunings of physical and electronic properties of metal complex-based functional materials.
    No preview · Article · Jan 2014 · Inorganic Chemistry
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    ABSTRACT: Ligation of 2,6-diphenylbenzenethiol (DppSH) onto Au clusters stabilized by poly(N-vinyl-2-pyrrolidone) and subsequent core etching yielded a single cluster Au25(SDpp)11. High-energy X-ray diffraction measurement showed that Au25 constitutes a core in Au25(SDpp)11. We propose a bi-icosahedral Au25 core whose 22 Au surface atoms are capped directly by 11 bulky arenethiolates.
    Preview · Article · Dec 2013 · Chemical Communications
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    ABSTRACT: A high-precision spin-coater system has been developed for the investigation of formation mechanisms of self-assembled structures in polymer thin films. The spin coater was designed to have small axial deflection (<2.6 µm at the maximum speed of 2000 r min−1) during rotation in order to maintain the relative position with respect to the incident X-ray beam, and to be compact (70 mm) in height to facilitate incorporation into an in situ synchrotron radiation grazing-incidence small-angle X-ray scattering (GISAXS) system. The first results of simultaneous measurements on the morphology and film thickness of a triblock copolymer with time resolution of 64 ms during thin-film formation at 2000 r min−1 provide indispensable information for understanding the vertically grown lamellar structure on the film surface.
    No preview · Article · Dec 2013 · Journal of Applied Crystallography
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    ABSTRACT: Alkali-metal-intercalated FeSe materials, (NH_{3})_{y}M_{0.4}FeSe (M: K, Rb, and Cs), have been synthesized using the liquid NH_{3} technique. (NH_{3})_{y}Cs_{0.4}FeSe shows a superconducting transition temperature (T_{c}) as high as 31.2 K, which is higher by 3.8 K than the T_{c} of nonammoniated Cs_{0.4}FeSe. The T_{c}s of (NH_{3})_{y}K_{0.4}FeSe and (NH_{3})_{y}Rb_{0.4}FeSe are almost the same as those of nonammoniated K_{0.4}FeSe and Rb_{0.4}FeSe. The T_{c} of (NH_{3})_{y}Cs_{0.4}FeSe shows a negative pressure dependence. A clear correlation between T_{c} and lattice constant c is found for ammoniated metal-intercalated FeSe materials, suggesting a correlation between Fermi-surface nesting and superconductivity.
    No preview · Article · Sep 2013 · Physical Review B

Publication Stats

2k Citations
431.42 Total Impact Points

Institutions

  • 2015
    • Kwansei Gakuin University
      Nishinomiya, Hyōgo, Japan
  • 2011-2015
    • Japan Synchrotron Radiation Research Institute (JASRI)
      Tatsuno, Hyōgo, Japan
    • The Electrochemical Society
      Society Hill, New Jersey, United States
  • 2002-2014
    • Japan Advanced Institute of Science and Technology
      • School of Materials Science
      KMQ, Ishikawa, Japan
  • 2013
    • RIKEN
      Вако, Saitama, Japan
  • 2012
    • Tohoku University
      • Department of Physics
      Sendai-shi, Miyagi, Japan
  • 2003-2012
    • Japan Science and Technology Agency (JST)
      Edo, Tōkyō, Japan
  • 1998-2002
    • The University of Tokyo
      • Department of Physics
      Tokyo, Tokyo-to, Japan
  • 2000
    • Tokyo Metropolitan University
      • Department of Physics
      Edo, Tokyo, Japan