Faculty Profiles - KOBAYASHI Makoto

Papers - KOBAYASHI Makoto

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Anisotropy in Conformation and Dynamics of a Glycolate Ion Near the Surface of a TiO<sub>2</sub> Rutile Crystal Between Its {001} and {110} Planes: A Molecular Dynamics Study Reviewed International journal

Hiroki Nada, Makoto Kobayashi, Masato Kakihana

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 120 ( 12 ) page： 6502 - 6514 2016.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

A molecular dynamics simulation was conducted to elucidate the conformation and dynamics of a glycolate ion (CH2(OH)COO-) at the surface of a TiO2 rutile crystal. The simulation was performed for the {001} and {110} planes of the crystal. The results indicate that, for both planes, the conformation and dynamics of the ion are strongly dominated by a layered structure of water on the surface. The simulation suggests that the ion binds to the surface more stably on the {110} plane than on the {001} plane, and that the stable conformation of the ion at the surface differs between the planes: on the {110} plane the carboxyl group of the ion is preferentially oriented toward the surface, whereas on the {001} plane it is oriented toward liquid water. These simulation results are compared with the growth shapes of rutile crystals synthesized in the presence of glycolic acid, and the role of glycolate ions in controlling the morphology of rutile crystals is discussed.

DOI： 10.1021/acs.jpcc.5b11087

Effect of Site Occupancies on Deep-red Emission from Eu2+-activated Ca2SiO4 Phosphor Reviewed International journal

Hiroki Kuwahara, Yasushi Sato, Hideki Kato, Makoto Kobayashi, Takaki Masaki, Masato Kakihana

CHEMISTRY LETTERS Vol. 45 ( 3 ) page： 321 - 323 2016.3

Language：English Publishing type：Research paper (scientific journal) Publisher：The Chemical Society of Japan

Calcium silicate cosubstituted with Sr<sup>2+</sup> and Eu<sup>2+</sup> was studied in order to examine the relationship between emission characteristics and Eu<sup>2+</sup> occupancy at two types of Ca sites (Ca(1<i>n</i>) and Ca(2<i>n</i>)). The results clearly indicate that red emission of the Ca<sub>2</sub>SiO<sub>4</sub>:Eu<sup>2+</sup> phosphor is caused by Eu<sup>2+</sup> substitution at the Ca(2<i>n</i>) site. In addition, red shift in emission of Eu(2<i>n</i>) occurs when large amounts of Eu were substituted.

DOI： 10.1246/cl.151145

Self-assembly of polyethyleneamine-intercalated H2Ti2O5 nanoparticles into spherical agglomerates Reviewed International journal

Makoto Kobayashi, Hideki Kato, Masato Kakihana

JOURNAL OF MATERIALS RESEARCH Vol. 31 ( 5 ) page： 564 - 572 2016.3

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：CAMBRIDGE UNIV PRESS

Although there are numerous reports on the synthesis of spherical materials, the development of new approaches remains important for theory construction to realize tailor-made synthesis of spherical materials. Herein, we report the synthesis of polydispersed spherical particles of H2Ti2O5 intercalated with a polyethyleneamine, such as an ethylenediamine, on the basis of a solvothermal treatment using concentrated polyethyleneamine aqueous solutions. The diameter of the micrometer-sized spheres enlarged with increasing amine concentration in the reaction solution. It was speculated that high ionic strength caused the self-assembly of polyethyleneamine-intercalated H2Ti2O5, resulting in the formation of spherical agglomerates. The spheres had a specific a surface area of 200 m(2) g(-1) and approximately 5 nm pores, and these values were controlled by amine concentration and treatment time. Conversion to single phase anatase and rutile without changes in spherical morphology was achieved by heat treatment. The present approach may assist with the design morphology of agglomerates.

DOI： 10.1557/jmr.2016.67

Hydrothermal Synthesis of Barium Tantalate Nanosheet Photocatalyst and Its Water Splitting Activity Reviewed

Soichi Takasugi, Koji Tomita, Michio Iwaoka, Makoto Kobayashi, Hideki Kato, Masato Kakihana

Journal of the Society of Inorganic Materials, Japan Vol. 23 ( 380 ) page： 25-29 2016

Crystal Growth of Titania Polymorphs by Hydrothermal Method(<Special Issue>Topics of Crystal Growth Related to Water) Invited Reviewed International journal Open Access

Kobayashi Makoto, Kato Hideki, Kakihana Masato

Journal of the Japanese Association for Crystal Growth Vol. 42 ( 4 ) page： 283-289 - 289 2016

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Association for Crystal Growth

Control of crystal growth is rather important in the field of materials, because the shape directly affects their functional abilities. Our research group engages in hydrothermal synthesis of titanium dioxide, which is regarded as one of the representative ceramics, using water-soluble titanium complexes. The high chemical stability and peculiar molecule structures of these titanium complexes allowed us to use various compounds which play a role in control of crystal growth, resulting in the selective synthesis of four titanium dioxide polymorphs, that is, rutile, anatase, brookite and TiO_2(B), with a controlled shape. This paper summarizes our past study and reported researches on synthesis of titania polymorph crystals by classification of zero-, one-, two-, and three-dimensional structures.

DOI： 10.19009/jjacg.42.4_283

Hydrothermal Synthesis of Barium Tantalate Nanosheet Photocatalyst and Its Water Splitting Activity Reviewed International journal

Soichi Takasugi, Koji Tomita, Michio Iwaoka, Makoto Kobayashi, Hideki Kato, Masato Kakihana

Journal of the Society of Inorganic Materials, Japan Vol. 23 ( 380 ) page： 25-29 2016

Synthesis of titania with controlled structures and its development Reviewed Open Access

小林亮

Journal of the Ceramic Society of Japan Vol. 掲載確定 2016

Graphene/MxWO3 (M = Na, K) nanohybrids with excellent electrical properties Reviewed International journal

Bin Liu, Shu Yin, Xiaoyong Wu, Yuhua Wang, Yunfang Huang, Jihuai Wu, Tohru Sekino, Junichi Matsushita, Soo Wohn Lee, Makoto Kobayashi, Masato Kakihana, Tsugio Sato

CARBON Vol. 94 page： 309 - 316 2015.11

Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD

Graphene/MxWO3 (M = Na, K) nanocomposites with different weight ratios were successfully synthesized using MBH4 as a reducing agent in aqueous solution, followed by crystallization of amorphous precursors under calcination in H-2 (5 vol.%)/N-2 atmosphere at 600 degrees C. The coupled samples showed good shielding properties in NIR wavelength range together with certain visible lights transparency. The as-prepared tungsten bronze nanoparticles are homogeneously anchored on graphene sheets, and the graphene/tungsten bronze nanocomposite showed an enhanced electrical conductivity with good shielding properties in the NIR range together with certain visible lights transparency. With the increment of graphene amount in the composites, the contact between the graphene sheets was enhanced, and the MxWO3 might enhance the charge transport properties of graphene by generating the short conductive path for electrons over the remained oxygenated functional groups. The synergistic effects could be observed in the composites. When 5 wt.% or more graphene were composed into MxWO3, the hybrid composite showed the higher electrical conductivity than those of uncoupled graphene and tungsten bronze alone. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.carbon.2015.06.072

Large Redshifts in Emission and Excitation from Eu<sup>2+</sup>-Activated Sr<sub>2</sub>SiO<sub>4</sub> and Ba<sub>2</sub>SiO<sub>4</sub> Phosphors Induced by Controlling Eu<sup>2+</sup> Occupancy on the Basis on Crystal-Site-Engineering Reviewed International journal Open Access

Yasushi Sato, Hiroki Kuwahara, Hideki Kato, Makoto Kobayashi, Takaki Masaki, Masato Kakihana

Optics and Photonics Journal Vol. 5 ( 11 ) page： 326-333 - 333 2015.11

Photoluminescence Properties of Mn4+-activated Perovskite-type Titanates, La2MTiO6:Mn4+ (M = Mg and Zn) Reviewed International journal Open Access

Yohei Takeda, Hideki Kato, Makoto Kobayashi, Hisayoshi Kobayashi, Masato Kakihana

CHEMISTRY LETTERS Vol. 44 ( 11 ) page： 1541 - 1543 2015.11

Language：English Publishing type：Research paper (scientific journal) Publisher：The Chemical Society of Japan

It has been found that Mn<sup>4+</sup>-activated La<sub>2</sub>MTiO<sub>6</sub> (M = Mg and Zn) functions as novel Eu-free phosphors for red emission in this work. La<sub>2</sub>MTiO<sub>6</sub>:Mn<sup>4+</sup> exhibited emission with a peak at 710 nm under excitation by ultraviolet to blue light (300–550 nm). La<sub>2</sub>MgTiO<sub>6</sub>:Mn<sup>4+</sup> exhibited stronger emission than La<sub>2</sub>ZnTiO<sub>6</sub>:Mn<sup>4+</sup>. The internal quantum yield of La<sub>2</sub>MgTiO<sub>6</sub>:Mn<sup>4+</sup> was 58.7% under the excitation at 330 nm.

DOI： 10.1246/cl.150748

A Facile One-Step Solvothermal Synthesis and Electrical Properties of Reduced Graphene Oxide/Rod-Shaped Potassium Tungsten Bronze Nanocomposite. Reviewed International journal

Bin Liu, Shu Yin, Yuhua Wang, Chongshen Guo, Xiaoyong Wu, Qiang Dong, Makoto Kobayashi, Masato Kakihana, Tsugio Sato

Journal of nanoscience and nanotechnology Vol. 15 ( 9 ) page： 7305 - 10 2015.9

Language：English Publishing type：Research paper (scientific journal)

Reduced graphene oxide (rGO)/rod-shaped potassium tungsten bronze nanocomposites with the different ratio were successfully synthesized by solvothermal reaction and followed by the reduction in H2(5 vol.%)/N2 atmosphere at 550 degrees C. The coupled samples showed excellent shielding ability of NIR light as well as certain visible lights transparency. The synergistic effects could be observed in the composites, i.e., when 15 wt% and 20 wt% of rGO which was fabricated by chemical reduction of graphene oxide, were composed into K(x)WO3, the composite showed the higher electrical conductivity than those of rGO and potassium tungsten bronze.

DOI： 10.1166/jnn.2015.10579

Synthesis of picolinate-iron(III) compounds through an aqueous solution process Reviewed International journal Open Access

Junki Sato, Makoto Kobayashi, Hideki Kato, Eunsang Kwon, Masato Kakihana

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 123 ( 1441 ) page： 751 - 755 2015.9

Language：English Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan

A novel picolinate-iron(III) compound, Fe(C<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>)<sub>2</sub>(OH) (<b>1</b>), was synthesized from an aqueous solution of a picolinate-iron(II) complex. Compound <b>1</b> was obtained by a thermal treatment of the picolinate-iron complex aqueous solution, whose pH was adjusted to 3–7, containing more than twice molar picolinic acid (Hpa) to Fe at 353 K for 72 h. When the iron aqueous solution in the presence of more than six times molar Hpa to Fe at pH 2–5 was heated, Fe(C<sub>6</sub>H<sub>4</sub>NO<sub>2</sub>)<sub>3</sub>·H<sub>2</sub>O (<b>2</b>) appeared. Millimeter-sized yellow-green single crystals of <b>2</b> could be obtained by the heat treatment of the picolinate-iron aqueous solution, whose pH was adjusted to 3, with Fe<sup>2+</sup>:Hpa = 1:10 at 373 K for 72 h. Formation mechanism of <b>1</b> and <b>2</b> was also discussed through investigations of relationship between synthesis conditions and products. Our approach opens a promising new route for preparation of precursors for synthesis of high functional ceramics and development of new organic–inorganic hybrids.

DOI： 10.2109/jcersj2.123.751

Novel Titanium Complexes with a Reversible Structural Change on Solvent Adsorption and Desorption Reviewed International journal

Makoto Kobayashi, Tatsuya Okuhara, Hideki Kato, Sota Sato, Masato Kakihana

CHEMISTRY LETTERS Vol. 44 ( 8 ) page： 1050 - 1052 2015.8

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Two novel pyrazine-2-carboxylate titanium complexes were synthesized from an aqueous solution (1) and 1 in N,N-dimethylformamide (DMF) (2). The structure of 2 was determined to be [Ti6O8(C4H3N2COO)(8)(C3H7NO)(4)]center dot 4C(3)H(7)NO center dot H2O by single-crystal X-ray analysis. Both complexes exhibited solvent adsorption desorption accompanying reversible structural change. 1 and 2 were compatible, and 1 was vital for the synthesis of 2. The degassed 1 showed gate adsorption property for water vapor.

DOI： 10.1246/cl.150393

Discovery of Novel Delafossite-type Compounds Composed of Copper(I) Lithium Titanium with Photocatalytic Activity for H-2 Evolution under Visible Light Reviewed International journal

Hideki Kato, Tsuyoshi Fujisawa, Makoto Kobayashi, Masato Kakihana

CHEMISTRY LETTERS Vol. 44 ( 7 ) page： 973 - 975 2015.7

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Novel delafossite-type compounds Cu(Li1/3Ti2/3)O-2 with 3R- and 2H-type structures have been discovered through the reaction between Li4Ti5O12 and Cu2O. Cu(Li1/3Ti2/3)O-2 is the first Cu(I)-titanate containing no d(n) (n = 1-9) metal ions. It has been found that Cu(Li1/3Ti2/3)O-2 with a band gap of 2.1 eV functions as a photocatalyst for H-2 evolution under visible light irradiation.

DOI： 10.1246/cl.150341

Hierarchical structures of rutile exposing high-index facets Reviewed International journal

Quang Duc Truong, Hideki Kato, Makoto Kobayashi, Masato Kakihana

JOURNAL OF CRYSTAL GROWTH Vol. 418 page： 86 - 91 2015.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Recently, shape-controlled synthesis of crystals exposing high-index facets has attracted much research interest due to their importance for both fundamental studies and technological applications. Herein, crystals of rutile-type TiO2 with hierarchical structures exposing high-index facets have been synthesized by a facile hydrothermal method using water-soluble titanium complex as a precursor and picolinic acid as structure-directing and shape-controlling agents. The synthesized particles were composed of several branches of pyramidal crystals with relatively smooth surface. On the basis of investigation results, it was speculated that the mutual pi-stacking and selective adsorption of picolinic acid on specific {111} facets resulted in the formation of rutile crystals bound by high-index surfaces such as {331}. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2015.02.056

Syntheses of silicate phosphors by aqueous solution techniques using water-dispersible inorganic Si cluster Reviewed International journal Open Access

Yasushi Sato, Hideki Kato, Makoto Kobayashi, Jihae Kim, Masato Kakihana

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy Vol. 62 ( 4 ) page： 127 - 133 2015.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Japan Society of Powder and Powder Metallurgy

ABSTRACT<BR><BR>In this paper, we demonstrated the synthesis of silicate-based phosphors by solution techniques using glycol-modified silane (GMS) as a Si source. GMS is a water-dispersible inorganic Si cluster, which is vitally involatile and nonflammable compounds, compared to volatile and flammable Si-alkoxides such as tetraethoxysilane (TEOS). Therefore, GMS has allowed the silicon containing compounds to be synthesized through various solution processes for ceramic compounds such as polymerizable complex (PC) and amorphous metal complex (AMC) methods. This paper provides examples of synthesis of new silicate-based phosphors such as NaAlSiO<sub>4</sub>:Eu<sup>2+</sup>, BaZrSi<sub>3</sub>O<sub>9</sub>:Eu<sup>2+</sup>, and CaSrSiO<sub>4</sub>:Eu<sup>2+</sup>. In addition, other examples of improvement of emission for conventional silicate-based phosphors, Y<sub>2</sub>SiO<sub>5</sub>:Ce<sup>3+</sup>-Tb<sup>3+</sup> and Zn<sub>2</sub>SiO<sub>4</sub>:Mn<sup>2+</sup>, prepared by the above solution techniques including homogeneous precipitation using GMS are also given in this paper.

DOI： 10.2497/jjspm.62.127

Design of crystal structures, morphologies and functionalities of titanium oxide using water-soluble complexes and molecular control agents Invited Reviewed International journal Open Access

Makoto Kobayashi, Minoru Osada, Hideki Kato, Masato Kakihana

POLYMER JOURNAL Vol. 47 ( 2 ) page： 78 - 83 2015.2

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Nature produces materials with excellent physical and chemical properties using water as a medium under ambient temperature and pressure. The current need for more highly functional and compact materials makes the mimicking of natural processes to produce these materials a very interesting approach, not only to obtain highly functionalized materials but also to reduce the environmental impact. Our research group is engaged in the development of new stable water-soluble compounds that follow natural processes for the synthesis of materials using water as a medium. This paper summarizes a hydrothermal synthesis of rutile-type titanium oxide using water-soluble titanium complexes, controlling the crystal morphology by utilizing organic molecules as shape-control agents as well as their speculative formation mechanism and superior dielectric properties of unusually shaped titanium oxide crystals. By recapitulating our results, we indicate that control of the nano-and macro-structures and functional improvement are accomplished through the development of new precursor compounds.

DOI： 10.1038/pj.2014.89

Crystal structures and luminescence properties of Eu²⁺-activated new NaBa0.5Ca0.5PO₄ and Na₃Ba₂Ca(PO₄)₃. Reviewed International journal

Minsung Kim, Makoto Kobayashi, Hideki Kato, Hisanori Yamane, Yasushi Sato, Masato Kakihana

Dalton transactions (Cambridge, England : 2003) Vol. 44 ( 4 ) page： 1900 - 4 2015.1

Language：English Publishing type：Research paper (scientific journal)

NaBa(1-x)Ca(x)PO4:Eu(2+) were synthesized using polymerizable complex method. New phases were observed at x = 1/3 and 0.5, which were identified by single-crystal XRD analysis as Na3Ba2Ca(PO4)3 and NaBa0.5Ca0.5PO4 with a trigonal system. Though both phases pretend to be solid solutions between NaBaPO4 and NaCaPO4, they have different coordination environments and PO4 orderings. 1 mol% Eu(2+)-activated NaBaPO4, Na3Ba2Ca(PO4)3, and NaBa0.5Ca0.5PO4 exhibited an emission maximum at 435 nm, 458 nm, and 460 nm, respectively. The shift of the emission maximum might be due to a change in the Eu-O bond length.

DOI： 10.1039/c4dt03024a

Controlled radical polymerization of styrene with magnetic iron oxides prepared through hydrothermal, bioinspired, and bacterial processes Reviewed International journal

Arihiro Kanazawa, Kotaro Satoh, Shokyoku Kanaoka, Masato Kakihana, Makoto Kobayashi, Junki Sato, Hiroaki Imai, Yuya Oaki, Atsushi Arakaki, Kiyofumi Katagiri, Masami Kamigaito, Sadahito Aoshima

RSC ADVANCES Vol. 5 ( 63 ) page： 51122 - 51129 2015

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Controlled/living radical polymerization was examined with the use of magnetic iron oxide (Fe3O4) prepared through various processes, including hydrothermal synthesis, a bioinspired process, and magnetotactic bacteria. Prior to the use of various types of Fe3O4, commercially available Fe3O4 was employed as a heterogeneous catalyst for styrene polymerization in conjunction with an alkyl halide as an initiator. Under appropriately optimized conditions, with the addition of Ph3P in a solvent mixture of toluene and DMF, the polymerization proceeded in a well-controlled manner. In addition, solid Fe3O4 was recovered using a magnetic approach and was reused for a polymerization reaction. The effects of stirring on the polymerization rate suggest that the surface of Fe3O4 is responsible for the catalysis in polymerization. Fe3O4 samples prepared through various processes were then used for styrene polymerization and showed different activities depending on the preparation process. In particular, Fe3O4 prepared through hydrothermal synthesis exhibited a much higher activity compared with commercial Fe3O4.

DOI： 10.1039/c5ra09149g

Photocatalytic water oxidation under visible light by valence band controlled oxynitride solid solutions LaTaON2-SrTiO3 Reviewed International journal

Kato, Hideki, Ueda, Koichiro, Kobayashi, Makoto, Kakihana, Masato

Journal of Materials Chemistry a Vol. 3 ( 22 ) page： 11824-11829 - 11829 2015

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