Takashi Kato

The University of Tokyo, Edo, Tōkyō, Japan

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Publications (253)1443.42 Total impact

  • [Show abstract] [Hide abstract]
    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; · 10.44 Impact Factor
  • Chemistry of Materials 11/2014; 26(22):6496-6502. · 8.54 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; · 3.49 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 09/2014; · 3.54 Impact Factor
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    ABSTRACT: Molecular assemblies that change photoluminescence color in response to thermal or mechanical stimulation without dissociation into the monomeric states in water are described herein. A dumbbell-shaped amphiphilic compound forms micellar molecular assemblies in water and exhibits yellow photoluminescence derived from excimer formation of the luminescent core, which contains a 2,6-diethynylanthracene moiety. Annealing of the aqueous solution induces a photoluminescence color change from yellow to green (λem, max=558525 nm). The same photoluminescence color change is also achieved by rubbing the yellow-photoluminescence-emitting molecular assemblies adsorbed on glass substrates with cotton wool in water. The observed green photoluminescence is ascribed to micelles that are distinct from the yellow-photoluminescence-emitting micelles, on the basis of transmission electron microscopy observations, atomic force microscopy observations, and dynamic light scattering measurements. We examined the relationship between the structure of the molecular assemblies and the photophysical properties of the anthracene derivative in water before and after thermal or mechanical stimulation and concluded that thermal or mechanical stimuli-induced slight changes of the molecular-assembled structures in the micelles result in the change in the photoluminescence color from yellow to green in water.
    Chemistry - A European Journal 07/2014; · 5.93 Impact Factor
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    ABSTRACT: The photocontrol of macroscopic alignment of nanostructured 2D ion-transporting pathways is described. The uniplanar homogenous alignment of thermotropic smectic (Sm) liquid-crystalline (LC) phase has been successfully achieved via photoinduced reorientation of the azobenzene groups of the imidazolium-based LC material. The ionic layers of the Sm LC phase are macroscopically oriented perpendicular to the surface of the glass substrate. The oriented films show anisotropic ion conduction in the Sm phase. This is the first example of the macroscopic photoalignment of ion-conductive LC arrays. Reversible switching of homeotropic and homogeneous alignments has also been achieved for the LC material. These materials and the alignment methodology may be useful in the development of ion-based circuits and memory devices.
    Journal of the American Chemical Society 06/2014; · 11.44 Impact Factor
  • Yulai Han, Tatsuya Nishimura, Takashi Kato
    Polymer Journal 05/2014; 46(8):499-504. · 1.55 Impact Factor
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    ABSTRACT: Covalent attachment of mechanoresponsive luminescent organic or organometallic compounds to other materials is a promising approach to develop a wide variety of mechanoresponsive luminescent materials. Here, we report covalently linkable mechanoresponsive micelles that change their photoluminescence from yellow to green in response to mechanical stimulation under aqueous conditions. These micelles are composed of a dumbbell-shaped amphiphilic pyrene derivative having amine groups at the peripheral positions of its dendrons. Using a well-established cross-linker, the micelles were covalently linked via their peripheral amine groups to the surface of glass beads, polylactic acid (PLA) beads, and living cells under aqueous conditions. Vortexing of glass beads bearing the micelles in a glass vial filled with water caused a photoluminescence color change from yellow to green. PLA beads bearing the micelles showed no change in photoluminescence color under the same conditions. We ascribe this result to the lower density and stiffness of the PLA beads, because the color of the PLA beads changed on vortexing in the presence of bare glass beads. HeLa cells and HL 60 cells bearing the micelles showed no obvious photoluminescence color change under vortexing. The structure, photophysical properties and mechanism of photoluminescence color change of the micellar assemblies were examined.
    Journal of the American Chemical Society 02/2014; · 11.44 Impact Factor
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    ABSTRACT: Nanostructured inorganic/polymer hybrid thin films comprising aragonite nanorods derived from aqueous suspensions of amorphous calcium carbonate (ACC) are prepared. For the formation of calcium carbonate (CaCO3 )/polymer hybrids, spincoated and annealed films of poly(vinyl alcohol) (PVA) that function as polymer matrices are soaked in aqueous colloidal solutions dispersing ACC stabilized by poly(acrylic acid) (PAA). In the initial stage, calcite thin films form on the surface. Subsequently, aragonite crystals start to form inside the PVA matrix that contains PVA crystallites which induce aragonite nucleation. Nanostructured hybrids composed of calcite thin films consisting of nanoparticles and assembled aragonite nanorods are formed in the matrices of PVA.
    Small 01/2014; · 7.51 Impact Factor
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    ABSTRACT: We here report the use of carboxylated polyrotaxanes as supramolecular templates for the formation of CaCO3 thin films. Polyrotaxanes consisting of carboxylated [small alpha]-cyclodextrins ([small alpha]-CD-COOH) and poly(ethylene glycol) have been obtained as an inducer of CaCO3 crystals. Poly(vinyl alcohol) has been used as a matrix to interact with the polyrotaxanes for this crystallization. These polyrotaxanes induce the formation of CaCO3 thin films, while the simple mixture of monomeric [small alpha]-CD-COOH and capped poly(ethylene glycol) only leads to the formation of granular crystals. The assembled carboxyl groups due to the construction of the polyrotaxane structure play an essential role for the development of CaCO3 thin films. Moreover, morphology and orientation of the obtained CaCO3 thin films are dependent on the amount of [small alpha]-CD-COOH incorporated into the polyrotaxane structure. This approach to the use of supramolecular templates will bring new designs for hybrid materials.
    CrystEngComm 01/2014; 16(8):1496-1501. · 3.86 Impact Factor
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    ABSTRACT: Switching of the luminescence properties of molecular materials in response to mechanical stimulation is of fundamental interest and also has a range of potential applications. Herein, a water-soluble mechanochromic luminescent pyrene derivative having two hydrophilic dendrons is reported. This pyrene derivative is the first example of a mechanochromic luminescent organic compound that responds to relative humidity. Mechanical stimulation (grinding) of this pyrene derivative in the solid state results in a change of the photoluminescence from yellow to green. Subsequent exposure to water vapor induces recovery of the initial yellow photoluminescence. The color change is reversible through at least ten cycles. It is also demonstrated that this compound can be applied as a mechano-sensing material in frictional wear testing for grease, owing to its immiscibility in non-polar solvents and its non-crystalline behavior. Transmission electron microscope and atomic force microscope observations of samples prepared from dilute aqueous solutions of the pyrene derivative on suitable substrates, together with dynamic light scattering measurements for the compound in aqueous solution, indicate that this amphiphilic dumbbell-shaped molecule forms micelles in water.
    Advanced Functional Materials 11/2013; 23(42). · 10.44 Impact Factor
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    ABSTRACT: Amino acid ionic liquids provide suitable media for lyotropic liquid-crystalline systems whose self-organisation behaviour is tuneable by the selection of amino acid anions.
    Chemical Communications 11/2013; · 6.38 Impact Factor
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    ABSTRACT: Molecular dynamics simulations were conducted to elucidate the effects of Mg2+ and H2O additives on the structure of amorphous calcium carbonate (ACC). New potential parameters for Mg2+ ions were developed. The distribution function of the angle formed by three nearest neighbor atoms was introduced to analyze the short-range, local structure of ACC. The simulation indicated that ACC had a weakly ordered local structure resembling the local structure of a CaCO3 crystal. The local structure of pure ACC resembled that of vaterite. The formation of the vaterite-like local structure was hindered by Mg2+ ions, whereas H2O molecules did not significantly influence the structure of ACC when the fraction of H2O molecules was low. However, when the fraction of H2O was high, the formation of a monohydrocalcite-like local structure was promoted. The effects of the additives on the structure of ACC were verified using the size of the additives, and the interaction between the additives and CaCO3. The simulated structure of ACC was compared with the structure of CaCO3 crystals nucleated through the formation of prenucleation ACC particles in real systems.
    The Journal of Physical Chemistry B 11/2013; · 3.38 Impact Factor
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    ABSTRACT: Herein we describe anhydrous proton transportation through 3D interconnected pathways formed by self-assembled molecular complexes. A thermotropic bicontinuous cubic (Cubbi) phase has been successfully obtained by mixing a wedge-shaped sulfobetaine with benzenesulfonic acid in different ratios. These ionic complexes exhibit the Cubbi phase in a wide range of temperatures while the single zwitterionic compound shows only a columnar hexagonal phase and benzenesulfonic acid is nonmesomorphic. Anhydrous proton conduction on the order of 10(-4) S cm(-1) has been achieved for the mixture in the Cubbi phase over 100 ºC, which can be useful for the development of new electrolytes for the next generation of fuel cells.
    Journal of the American Chemical Society 10/2013; · 11.44 Impact Factor
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    ABSTRACT: Thin-film growth of aragonite CaCO3 on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg(2+) into a supersaturated solution of CaCO3 . Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg(2+) in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg(2+) . Molecular dynamics simulation of the CaCO3 precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg(2+) . The role for ionic additives in the crystallization of CaCO3 on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.
    Chemistry - An Asian Journal 09/2013; · 4.57 Impact Factor
  • Japanese Journal of Applied Physics 06/2013; 52(6S):06GF04. · 1.06 Impact Factor
  • Junji Sakuda, Takuma Yasuda, Takashi Kato
    ChemInform 04/2013; 44(17).
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    ABSTRACT: Smectic liquid crystals consisting of an aromatic moiety based on 10,10′-bis(phenylethynyl)-9,9′-bianthryl at the central part and one and two mesogenic moieties on each side connected through oxyethylene spacers have been prepared to develop stimuli-responsive materials. The compound having two mesogenic moieties on each side (i.e. four total) forms an ordered smectic phase. Mechanochromic luminescence is observed for the smectic liquid crystal. A sample of this molecule formed by thermal annealing shows green photoluminescence at room temperature. The photoluminescent color changes from green to blue-green with mechanical stimulation at room temperature. The change of the photoluminescent color by mechanical shearing is ascribed to the disturbance of the π–π interactions between the adjacent molecules. Moreover, the original green photoluminescent color is recovered by heating followed by cooling to room temperature. The effects of the number, and thus volume of mesogenic moieties were also examined. Smaller mesogenic moieties lead to stronger ground state interactions between adjacent luminescent molecules and red-shifted emission. In contrast, the compound having three mesogenic moieties on each side shows no mechanochromic luminescence. The large mesogenic moieties disturb intermolecular interactions, resulting in no detectable change in the assembled structure of luminescent moieties upon mechanical stimulation. These results suggest that the present molecular design is useful for fabricating new stimuli-responsive materials with liquid-crystalline behavior.
    J. Mater. Chem. C. 03/2013; 1(15):2648-2656.
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    ABSTRACT: Functional peptides play an important role in the formation of biominerals. Here we focus on peptides involved in mineralization of the exoskeleton of a crayfish. New recombinant peptides are designed and synthesized on the basis of an acidic functional peptide, CAP-1, derived from the exoskeleton of a crayfish. We have examined the effect of these peptides on the hybrid formation of calcium carbonate and organic molecules in aqueous solution. In the presence of these recombinant peptides having chitin binding moieties, platelike tripodal calcite crystals are formed on the chitin matrix with unidirectional crystallographic orientation. Two kinds of interactions, (1) interactions between an acidic part of the peptides and calcium ions and (2) specific binding interactions of the peptides to chitin, are essential for the formation of the oriented crystals and the induction of specific morphologies. Moreover, the sizes of crystallites decrease with increasing the number of acidic parts of mutational peptides. The bioinspired design of peptides that control the interface of inorganic and organic domains may pave the way for an opportunity to build new hybrid structures.
    Faraday Discussions 03/2013; 159(1):483-494. · 4.19 Impact Factor
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    ABSTRACT: The introduction of bulky tert-butyl substituents into smectic liquid-crystalline 9,10-bis(phenylethynyl)anthracene derivatives influences excimer structures and luminescence properties.
    Chemical Communications 02/2013; · 6.38 Impact Factor

Publication Stats

4k Citations
1,443.42 Total Impact Points


  • 1970–2014
    • The University of Tokyo
      • • Department of Medical Engineering
      • • Department of Chemistry and Biotechnology
      • • Faculty & Graduate School of Engineering
      • • Institute of Industrial Science
      Edo, Tōkyō, Japan
  • 2005–2013
    • Tokyo University of Agriculture and Technology
      Edo, Tōkyō, Japan
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan
  • 2007
    • Kyoto University
      • Department of Material Chemistry
      Kyoto, Kyoto-fu, Japan
    • University of California, Los Angeles
      • Department of Chemistry and Biochemistry
      Los Angeles, CA, United States
  • 2002
    • Tokyo Institute of Technology
      • Chemical Resources Laboratory
      Tokyo, Tokyo-to, Japan