Takashi Kato

Kansai University, Suika, Ōsaka, Japan

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Publications (301)1704.69 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The possibility to change the molecular assembled structures of organic and organometallic materials through mechanical stimulation is emerging as a general and powerful concept for the design of functional materials. In particular, the photophysical properties such as photoluminescence color, quantum yield, and emission lifetime of organic and organometallic fluorophores can significantly depend on the molecular packing, enabling the development of molecular materials with mechanoresponsive luminescence characteristics. Indeed, an increasing number of studies have shown in recent years that mechanical force can be utilized to change the molecular arrangement, and thereby the optical response, of luminescent molecular assemblies of π-conjugated organic or organometallic molecules. Here, the development of such mechanoresponsive luminescent (MRL) molecular assemblies consisting of organic or organometallic molecules is reviewed and emerging trends in this research field are summarized. After a brief introduction of mechanoresponsive luminescence observed in molecular assemblies, the concept of "luminescent molecular domino" is introduced, before molecular materials that show turn-on/off of photoluminescence in response to mechanical stimulation are reviewed. Mechanically stimulated multicolor changes and water-soluble MRL materials are also highlighted and approaches that combine the concept of MRL molecular assemblies with other materials types are presented in the last part of this progress report.
    Advanced Materials 10/2015; DOI:10.1002/adma.201502589 · 17.49 Impact Factor
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    ABSTRACT: We demonstrate switching of ionic conductivities in wedge-shaped liquid-crystalline (LC) ammonium salts. A thermoreversible phase transition between the rectangular columnar (Colr) and hexagonal columnar (Colh) phases is used for the switch. The ionic conductivities in the Colh phase are about four orders of magnitude higher than those in the Colr phase. The switching behavior of conductivity can be ascribed to the structural change of assembled ionic channels. X-ray experiments reveal a highly ordered packing of the ions in the Colr phase which prevent the ion transport.
    Journal of the American Chemical Society 09/2015; DOI:10.1021/jacs.5b09076 · 12.11 Impact Factor
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    ABSTRACT: Liquid-crystalline CaCO3 has been prepared for the first time. The nanorods of CaCO3 calcite are obtained by bio-inspired crystallization through aqueous colloidal precursors of amorphous CaCO3 stabilized by poly(acrylic acid). The synthesized calcite nanocrystals have well-tuned morphologies that are preferable for formation of liquid-crystalline phases in concentrated aqueous colloidal solution. The one-dimensional alignment of calcite crystals is achieved by mechanical shearing of the aqueous colloidal solution showing liquid-crystalline phases. These CaCO3-based liquid crystals formed by a self-organization process in mild conditions may have great potential for use as environmentally friendly materials. This journal is
    Chemical Science 08/2015; 6(11). DOI:10.1039/C5SC01820J · 9.21 Impact Factor
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    ABSTRACT: Chitin/CaCO3 hybrids with helical structures are formed through a biomineralization-inspired crystallization process under ambient conditions. Liquid-crystalline chitin whiskers are used as helically ordered templates. The liquid-crystalline structures are stabilized by acidic polymer networks which interact with the chitin templates. The crystallization of CaCO3 is conducted by soaking the templates in the colloidal suspension of amorphous CaCO3 (ACC) at room temperature. At the initial stage of crystallization, ACC particles are introduced inside the templates, and they crystallize to CaCO3 nanocrystals. The acidic polymer networks induce CaCO3 crystallization. The characterization of the resultant hybrids reveals that they possess helical order and homogeneous hybrid structures of chitin and CaCO3 , which resemble the structure and composition of the exoskeleton of crustaceans. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Small 07/2015; 11(38). DOI:10.1002/smll.201501083 · 8.37 Impact Factor
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    ABSTRACT: Macroscopically ordered inorganic thin films have been formed on unidirectionally oriented, liquid-crystalline chitin matrices. In the presence of poly(acrylic acid), unidirectionally oriented chitin films act as templates for the formation of oriented thin-film crystals of alkaline-earth carbonate, SrCO3 and BaCO3. The morphology and orientation of crystals are dependent on the metal ion concentration. For SrCO3 crystallization, unidirectional thin films and hexagonal-shaped thin films have been deposited from 200 and 25 mM concentration strontium solutions, respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - An Asian Journal 07/2015; DOI:10.1002/asia.201500462 · 4.59 Impact Factor
  • Masahiro Funahashi · Takashi Kato ·
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    ABSTRACT: It is fundamentally important to study the relationships between structures and properties of liquid crystals. Professor G.W. Gray developed new rod-like nematic liquid crystals, 4-alkyl- and 4-alkoxy-4ʹ-cyanobiphenyls, which act as materials for stable informational liquid crystal displays. This molecule was invented based on his deep understanding of the relationships of chemical structure and physical properties of liquid crystals. After the discovery of nematogenic liquid crystals for display application, the advent of the molecular design and synthesis of liquid crystals has produced a variety of new family of functional liquid crystals. For example, as a new twist of rigid rod mesogens, oligothiophene rings have emerged recently. Due to their extended π-conjugated systems, oligothiophene-based liquid crystals exhibit various electronic and optical functions. In this review, we describe the impact of Professor Gray’s nematic liquid crystals as well as the structures and functions of oligothiophene-based liquid crystals.
    Liquid Crystals 06/2015; 42(5):1-9. DOI:10.1080/02678292.2015.1025876 · 2.49 Impact Factor
  • Takashi Kato · Takeshi Sakamoto · Yosuke Nishimura ·
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    ABSTRACT: We here report the use of photolithographic polymer thin films as matrices for the formation of inorganic/organic polymer thin-film hybrids and the tuning of their structures. Poly(vinyl alcohol) derivatives bearing photoreactive styrylpyridinium moieties (PVA-SbQs) are used as matrices for the crystallization of CaCO3 and SrCO3. Thin-film hybrids are formed on the matrices in the presence of poly(acrylic acid). The polymorphs and morphologies of the CaCO3 nanocrystal assemblies are tuned by the photoreaction and the polymer structures of the matrices. Hybrid CaCO3 films exhibiting complex shapes and different surface structures are formed on the photoimaged PVA-SbQ matrix. Crystallization of SrCO3 on the photoimaged matrix leads to selective formation of film hybrids on UV-irradiated areas. These approaches may have great potential in controlling the complex structures of inorganic/polymer composite materials.
    CrystEngComm 04/2015; 17(36). DOI:10.1039/C5CE00451A · 4.03 Impact Factor
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    ABSTRACT: A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57 Å between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3×10(-5) cm(2) V(-1) s(-1) , respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Angewandte Chemie International Edition 04/2015; 54(23). DOI:10.1002/anie.201502678 · 11.26 Impact Factor
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    ABSTRACT: Ionic liquid-based 2D ion-conductive liquid crystals are obtained by co-assembly of imidazolium salts and cationic calamitic liquid crystals with an imidazolium moiety at the end of the molecule through a flexible spacer. They exhibit smectic A phases. The two components are compatible over a wide range of compositions for ionic liquids with various anions. This organization of ionic liquids enhances the ionic conductivities of calamitic ionic liquid crystals. These liquid-crystalline mixtures dissolve lithium salts. The 2D ion-conductive pathways formed by the ionic liquid crystals and ionic liquids act as ion-conductive media for lithium ions.
    New Journal of Chemistry 03/2015; 39(6). DOI:10.1039/C5NJ00085H · 3.09 Impact Factor
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    ABSTRACT: We describe the development of self-assembled one- and three-dimensional lithium ion conductors composed of zwitterionic liquid crystals, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and propylene carbonate (PC). Two types of wedge-shaped zwitterions based on imidazolium dicyanoethenolate and sulfonate were synthesized. These compounds alone show liquid-crystalline (LC) columnar hexagonal (Colh) phases and low ionic conductivities (10-8-10-7 S cm-1). The increase in the ionic conductivities was achieved by the addition of LiTFSI (10-5 S cm-1) followed by that of PC (10-4 S cm-1). Moreover, LC bicontinuous cubic (Cubbi) phases are induced by tuning the ionic nature of the zwitterionic liquid crystal with the ratio of LiTFSI and PC. The dissociation of LiTFSI in the zwitterions and the ion-dipole interaction between the lithium ion and PC are shown to be significant keys for the enhancement of the conductivities and stabilization of the nanosegregated LC structures.
    03/2015; 3(21). DOI:10.1039/C5TA00814J
  • Takashi Kato · Hirotsugu Kikuchi · Hiroaki Imai ·
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    ABSTRACT: Polymer Journal, official journal of the Society of Polymer Science, Japan publishes high quality papers in all areas of polymer and macromolecular research.
    Polymer Journal 02/2015; 47(2):77-77. DOI:10.1038/pj.2014.132 · 1.65 Impact Factor
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    ABSTRACT: Ionic liquids have attracted a considerable attention as the next generation electrolytes for energy devices. We have developed new free-standing and nanostructured polymer films in which ionic liquids are confined into one-dimensionally ordered nanochannels. These polymer films have been obtained by photopolymerization of hydrogen-bonded supramolecular columnar liquid-crystalline self-assemblies of an imidazolium-based ionic liquid and a wedge-shaped diol compound containing polymerizable groups. The macroscopically parallel alignment of the columnar structures on a glass substrate has been achieved by the application of mechanical shearing, and subsequently fixed into polymer films by UV irradiation. This ionic liquid-containing polymer film exhibits higher ionic conductivity than that of the previously reported one-dimensional polymer film obtained by in situ photopolymerization of a covalent-type columnar liquid-crystalline imidazolium salt. The noncovalent supramolecular approach to one-dimensionally ion-conductive polymer films has led to improvement on conductive properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014
    Journal of Polymer Science Part A Polymer Chemistry 01/2015; 53(2). DOI:10.1002/pola.27380 · 3.11 Impact Factor

  • Journal of Materials Chemistry A 01/2015; DOI:10.1039/C5TA06414G · 7.44 Impact Factor
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    ABSTRACT: Recently, there has been increasing attention on the design of nanostructured materials having gyroid structures due to their unique three-dimensionally ordered structures. In this paper, bicontinuous cubic liquid crystal, one of representative materials that form gyroid structure, is discussed. There have been only a small number of researches on liquid-crystalline molecules exhibiting thermotropic bicontinuous cubic phases, and therefore it is difficult to design bicontinuous cubic liquid crystals. We have succeeded in overcoming the difficulty by introducing designability of ionic liquids into liquid crystal design. In this paper, we describe self-organizing ionic liquids that show bicontinuous cubic liquid-crystalline phases. Furthermore, their potential application as novel nanochannel materials is described.
    01/2015; 57(3):184-190. DOI:10.5940/jcrsj.57.184
  • Fangjie Zhu · Tatsuya Nishimura · Takashi Kato ·
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    ABSTRACT: In this work, fluorescent and azo dyes were incorporated into CaCO3 and cyclodextrin (CD)-based network polymer thin-film hybrids through host-guest interactions. The hybrid films were prepared on poly(CD)s by a one-pot CaCl2 and Na2CO3 solution process in the presence of poly(acrylic acid). The hybrid-thin films containing fluorescent dyes demonstrate homogeneous fluorescence. The photoisomerization of azo dyes is observed in the solid thin-film hybrids. © 2015 The Society of Polymer Science, Japan (SPSJ) All rights reserved.
    Polymer Journal 12/2014; 47(2):122-127. DOI:10.1038/pj.2014.123 · 1.65 Impact Factor
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    ABSTRACT: Biomimetic processing using a solution mimicking the inorganic composition of the body fluid of humans (simulated body fluid (SBF)) may be one of the more promising routes for the construction of polymer/hydroxyapatite composites by an environmental-friendly method. In this process, hydroxyapatite nucleation on an organic polymer is an important event, yet the optimal surface characteristics of the organic polymer have not been determined. In the present study, a series of oxidized cellulose nanofibers with different contents of the carboxy groups (0-27% per glucose units of cellulose) were prepared. Their capability of forming hydroxyapatite in 1.5SBF (a solution in which the concentration of the inorganic ions was 1.5 times higher than that in SBF) was systematically investigated. It was found that hydroxyapatite formation on the nanofibers was the most enhanced with a nanofiber containing a carboxy group content of 9.9%, indicating that there was an optimum amount of carboxy groups that was required for the effective induction of hydroxyapatite nucleation. Carboxy groups are considered to be involved in the electrostatic interactions between the fibers and the calcium ions in solution and they induce heterogeneous nucleation of hydroxyapatite. Higher contents of carboxy groups, however, reduced the activity of the calcium ions for the nucleation of hydroxyapatite by forming complexes with the calcium ions.
    Polymer Journal 12/2014; 47(2):158-163. DOI:10.1038/pj.2014.127 · 1.65 Impact Factor
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    ABSTRACT: Thermotropic liquid-crystalline (LC) electrolytes for lithium-ion batteries are developed for the first time. A rod-like LC molecule having a cyclic carbonate moiety is used to form self-assembled two-dimensional ion-conductive pathways with lithium salts. Electrochemical and thermal stability, and efficient ionic conduction is achieved for the liquid crystal. The mixture of the carbonate derivative and lithium bis(trifluoromethylsulfonyl)imide is successfully applied as an electrolyte in lithium-ion batteries. Reversible charge–discharge for both positive and negative electrodes is observed for the lithium-ion batteries composed of the LC electrolyte.
    Advanced Functional Materials 12/2014; 25(8). DOI:10.1002/adfm.201402509 · 11.81 Impact Factor
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    ABSTRACT: Nanostructured liquid-crystalline (LC) ion transporters have been developed and applied as new electrolytes for dye-sensitized solar cells (DSSCs). The new electrolytes are two-component liquid crystals consisting of a carbonate-based mesogen and an ionic liquid that self-assemble into two-dimensional (2D) nanosegregated structures forming well-defined ionic pathways suitable for the I–/I3– redox couple transportation. These electrolytes are nonvolatile and they show LC phases over wide temperature ranges. The DSSCs containing these electrolytes exhibit exceptional open-circuit voltages (Voc) and improved power conversion efficiencies with increasing temperature. Remarkably, these solar cells operate at temperatures up to 120 °C, which is, to the best of our knowledge, the highest working temperature reported for a DSSC. The nature of the LC electrolyte and the interactions at the TiO2 electrode/electrolyte interface lead to a partial suppression of electron recombination reactions, which is key in the exceptional features of these LC-DSSCs. Thus, this type of solar cells are of interest, because they can produce electricity efficiently from light at elevated temperatures.
    Chemistry of Materials 11/2014; 26(22-22):6496-6502. DOI:10.1021/cm503090z · 8.35 Impact Factor
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    ABSTRACT: Organisms produce various organic/inorganic hybrid materials, which are called biominerals. They form through the self-organization of organic molecules and inorganic elements under ambient conditions. Biominerals often show highly organized and hierarchical structures from nanometer to macroscopic length scales, resulting in remarkable physical and chemical properties that cannot be obtained by simple accumulation of their organic and inorganic constituents. These observations motivate us to create novel functional materials exhibiting properties superior to those of conventional materials-both synthetic and natural. Herein, we introduce recent progresses in understanding biomineralization processes at molecular levels and the development of organic/inorganic hybrid materials by these processes. We specifically outline fundamental molecular studies on silica, iron oxide, and calcium carbonate biomineralization and describe material synthesis based on these mechanisms. These approaches allow us to design a variety of advanced hybrid materials with desired morphologies, sizes, compositions, and structures through environmentally friendly synthetic routes using functions of organic molecules.
    Organic & Biomolecular Chemistry 10/2014; 46(11). DOI:10.1039/C4OB01796J · 3.56 Impact Factor

Publication Stats

11k Citations
1,704.69 Total Impact Points


  • 2013
    • Kansai University
      Suika, Ōsaka, Japan
  • 1970-2013
    • The University of Tokyo
      • • Department of Chemistry and Biotechnology
      • • Department of Chemistry
      • • Institute of Industrial Science
      Edo, Tōkyō, Japan
  • 2002
    • Kyoto University
      • Department of Material Chemistry
      Kioto, Kyōto, Japan
  • 2000
    • Radboud University Nijmegen
      • Department of Organic Chemistry
      Nymegen, Gelderland, Netherlands
  • 1989-1996
    • Cornell University
      Итак, New York, United States