Takashi Kato

Kansai University, Suika, Ōsaka, Japan

Are you Takashi Kato?

Claim your profile

Publications (293)1615.14 Total impact

  • [Show abstract] [Hide abstract]
    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; DOI:10.1002/smll.201501083 · 7.51 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 3.94 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Photolithographic polymer films are used as crystallization matrices for the development of inorganic/organic polymer thin-film hybrids. The polymorphs and morphology of the CaCO3 nanocrystals assemblies are tuned by the photoreaction and polymer structures of the matrices. Crystallization using photoimaged matrices results in the formation of hybrid films having various hierarchically ordered structures.
    CrystEngComm 04/2015; DOI:10.1039/C5CE00451A · 3.86 Impact Factor
  • [Show abstract] [Hide abstract]
    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
  • [Show abstract] [Hide abstract]
    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 · 3.16 Impact Factor
  • [Show abstract] [Hide abstract]
    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
  • Polymer Journal 02/2015; 47(2):77-77. DOI:10.1038/pj.2014.132 · 1.55 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    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.
    Polymer Journal 12/2014; 47(2):122-127. DOI:10.1038/pj.2014.123 · 1.55 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 1.55 Impact Factor
  • [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; 25(8). DOI:10.1002/adfm.201402509 · 11.81 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 8.54 Impact Factor
  • [Show abstract] [Hide abstract]
    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 · 3.49 Impact Factor
  • [Show abstract] [Hide abstract]
    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 08/2014; 20(33). DOI:10.1002/chem.201403025 · 5.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We prepared pyridinium-based amphiphilic zwitterions and examined their liquid-crystalline (LC) phase behavior in the presence and absence of lithium salts. Addition of lithium salts induced nanosegregated LC phases such as bicontinuous cubic phase and smectic phase depending on the anion species of the lithium salts. For example, an equimolar mixture of dodecylcarbamoyl-1-(4-sulfobutyl)pyridinium betaine and lithium bis(trifluoromethanesulfonyl)imide (LiTf2N) exhibited a bicontinuous cubic phase between 40 and 100 C. The exhibition of these nanosegregated phases was attributed to the formation of an ionic liquid-like ion pair composed of the pyridinium cation and the Tf2N anion. The preferential interaction between the pyridinium cation and the Tf2N anion was confirmed with Raman spectroscopic measurement. Moreover, the amphiphilic zwitterions were found to show not only thermotropic LC behavior but also lyotropic LC behavior in the presence of polar solvents such as protic ionic liquids. The results presented here indicate that the combination of amphiphilic zwitterions and suitable additive ions is a potential method to construct nanostructured LC materials showing tuneable phase behavior.
    Bulletin of the Chemical Society of Japan 07/2014; 87(7):792-796. DOI:10.1246/bcsj.20140049 · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    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; 136(27). DOI:10.1021/ja5041573 · 11.44 Impact Factor
  • Yulai Han, Tatsuya Nishimura, Takashi Kato
    [Show abstract] [Hide abstract]
    ABSTRACT: Thermoresponsive poly(N-isopropylacrylamide) (PNIPAm) brushes have been synthesized and employed as the crystallization matrices for the development of polymer/strontium carbonate hybrid materials. The use of PNIPAm brush matrices results in the formation of patterned polymer/strontium carbonate hybrid thin films in the presence of poly(acrylic acid) additives. Moreover, the conformational change in the thermoresponsive PNIPAm brush matrices induces the change in the surface morphologies of the obtained polymer/SrCO3 hybrid thin films. The strategy of using stimuli-responsive polymer brush matrices is expected to be a promising method for controlling the surface morphology of two-dimensional hybrid thin film materials.
    Polymer Journal 05/2014; 46(8):499-504. DOI:10.1038/pj.2014.36 · 1.55 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 5,5′-Bis(2-phenylethynyl)-2,2′-bithiophene derivative 1 containing dendritic moieties linked through amide groups was synthesized. Compound 1 exhibits a rectangular columnar phase on slow cooling from the isotropic liquid. In contrast, a cubic phase is formed as a metastable liquid-crystalline phase by rapid cooling of the isotropic melt. Mechanical shearing induces a cubic–columnar phase transition, accompanied by the change of a photoluminescent color from yellow-green to green. The infrared spectra of 1 suggest that the mechanical stimuli can induce the partial dissociation of the hydrogen bond. This may lead to more disordering of the π-stacks of chromophores.
    Molecular Crystals and Liquid Crystals 05/2014; 594(1):112-121. DOI:10.1080/15421406.2014.917499 · 0.49 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Stiff yet flexible and strong transparent film materials mimicking the structure of crustacean exoskeletons were obtained from calcium carbonate and cellulose. These biobased materials have the composite structure of a three-dimensional nanoscale network of surface-carboxylated crystalline cellulose incorporated into an amorphous inorganic-based hybrid matrix of nanosegregated calcium carbonate and acidic polymers.
    05/2014; 1(3):321. DOI:10.1039/c3mh00134b
  • [Show abstract] [Hide abstract]
    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 04/2014; 10(8). DOI:10.1002/smll.201302745 · 7.51 Impact Factor

Publication Stats

9k Citations
1,615.14 Total Impact Points

Institutions

  • 2013
    • Kansai University
      Suika, Ōsaka, Japan
  • 1970–2013
    • The University of Tokyo
      • • Department of Chemistry and Biotechnology
      • • Institute of Industrial Science
      Edo, Tōkyō, Japan
  • 2005
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan
  • 2002–2004
    • Shinshu University
      Shonai, Nagano, Japan
    • Kyoto University
      • Department of Material Chemistry
      Kioto, Kyōto, Japan
  • 1998–2001
    • Shimane University
      • Department of Physics and Material Science
      Matsu, Shimane, Japan
  • 2000
    • Radboud University Nijmegen
      • Department of Organic Chemistry
      Nymegen, Gelderland, Netherlands
  • 1989–1996
    • Cornell University
      Итак, New York, United States