Faculty Profiles - KOBAYASHI Makoto

Papers - KOBAYASHI Makoto

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Exploration of New Phosphors Using a Mineral-Inspired Approach in Combination with Solution Parallel Synthesis Invited Reviewed International journal

Masato Kakihana, Jihae Kim, Tetsufumi Komukai, Hideki Kato, Yasushi Sato, Makoto Kobayashi, Yuji Takatsuka

Optics and Photonics Journal Vol. 3 ( 6A ) page： 5-12 2013.10

Synthesis of a Novel Bluish-Green Emitting Oxynitride Ca₃Al₈Si₄O₁₇N₄:Eu⁺² Phosphor in a CaAl_4-xSi_xO_7-xN_x Solid Solution Reviewed International journal

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

Optics and Photonics Journal Vol. 3 ( 6A ) page： 29-33 2013.10

Enhanced Dielectric Response Induced by Controlled Morphology in Rutile TiO₂ Nanocrystals Reviewed

Minoru Osada, Makoto Kobayashi, Masato Kakihana

Journal of the Ceramic Society of Japan Vol. 121 ( 8 ) page： 593-597 2013.8

Synthesis of new thiogallate phosphors (Ba_1-xSr_x)₄Ga₂S₇:Eu and their luminescence properties Reviewed

Kohei Takeuchi, Takahiko Hasegawa, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest page： 260-260 2013.8

Luminescence properties of a novel green-emitting phosphate phosphor KSrY(PO₄)₂:Eu²⁺ Reviewed

Akiko Saito, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest page： 261-261 2013.8

Luminescence properties of a novel green-emitting phosphate phosphor KSrY(PO₄)₂:Eu²⁺ Reviewed International journal

Akiko Saito, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest page： 261-261 2013.8

Synthesis of new thiogallate phosphors (Ba_1-xSr_x)₄Ga₂S₇:Eu and their luminescence properties Reviewed International journal

Kohei Takeuchi, Takahiko Hasegawa, Hideki Kato, Makoto Kobayashi, Masato Kakihana

IMID 2013 Digest page： 260-260 2013.8

Synthesis of a LiCaPO₄:Eu²⁺ phosphor by a polymerizable complex method using a novel water-soluble phosphate precursor International journal

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

IMID 2013 Digest page： 264 - 264 2013.8

Photocatalytic Water Splitting over LaTa₇O₁₉ Composed of TaO₇ Pentagonal Bipyramids and TaO₆ Octahedra Reviewed International journal

Hideki Kato, Arisa Takeda, Makoto Kobayashi, Masato Kakihana

Chemistry Letters Vol. 42 ( 7 ) page： 744 - 746 2013.7

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

It has been found that cocatalyst-loaded LaTa7O19 with a band gap of 4.1 eV functions as a photocatalyst for water splitting under ultraviolet irradiation. The activity of Rh0.5Cr1.5O3-loaded LaTa7O19 prepared by a polymerizable complex method exhibited double of that prepared by a solid-state reaction. An apparent quantum yield of Rh0.5Cr1.5O3-loaded LaTa7O19 was determined to be 9.0% at 254 nm.

DOI： 10.1246/cl.130216

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Effect of carboxyl group on the visible-light photocatalytic activity of SrTiO3 nanoparticles Reviewed International journal

Huihui Li, Shu Yin, Yuhua Wang, Makoto Kobayashi, Satoko Tezuka, Masato Kakihana, Tsugio Sato

RESEARCH ON CHEMICAL INTERMEDIATES Vol. 39 ( 4 ) page： 1615 - 1621 2013.4

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

SrTiO3 nanoparticles modified with a carboxyl group were successfully prepared by microwave-assisted solvothermal reaction of SrCl2 center dot 6H(2)O and Ti(OC3H7)(4) in methanol-organic acid solution. The as-prepared products were characterized using X-ray diffraction (XRD), diffuse reflectance spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The photocatalytic activity was determined by DeNO (x) ability using a mercury arc with filters to control irradiation wavelengths to > 290, > 400, and > 510 nm. Nanoparticles of perovskite-type SrTiO3 were successfully synthesized above pH 12. The photocatalytic activity of SrTiO3 under visible-light (> 510 nm) irradiation could be promoted by surface modification of SrTiO3 with the carboxyl group (-COO), especially from oleic acid.

DOI： 10.1007/s11164-012-0894-1

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水を溶媒に用いた機能性酸化物の低温合成のためのグリーンプレカーサーの開発 Invited Reviewed

小林亮, 垣花眞人

機能材料 Vol. 33 ( 1 ) page： 4-10 2013.1

Control of Valence Band Potential and Photocatalytic Properties of Na_xLa_1-xTaO_1+2xN_2-2x Oxynitride Solid Solutions Reviewed International journal

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

Journal of Materials Chemistry A Vol. 1 ( 11 ) page： 3667 - 3674 2013

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

A series of oxynitride solid solutions, NaxLa1-xTaO1+2xN2-2x with x 0.1, 0.2, 0.25, 0.3, 0.5, 0.75 and 0.85, was successfully synthesized by nitridation of amorphous oxide precursors under an NH3 stream at 1273 K. The band gaps of the solid solutions increased with the Na content. Photoelectrochemical analysis was conducted to obtain information on the band potentials of the solid solutions. The valence band maxima of the solid solutions were at more positive potentials than that of LaTaON2 (x = 0). Solid solutions of NaxLa1-xTaO1+2xN2-2x with x = 0.20-0.85 exhibited photocatalytic activity for both H-2 and O-2 evolution under visible light irradiation in the presence of sacrificial reagents, while LaTaON2 had no activity for O-2 evolution. The achievement of O-2 evolution with these solid solutions is due to control of the valence band potential; therefore, control of the photocatalytic properties of LaTaON2 was achieved by the formation of solid solutions.

DOI： 10.1039/c3ta10257b

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Enhancement of luminescence properties of a KSrPO₄:Eu²+ phosphor prepared using a solution method with a water-soluble phosphate oligomer Reviewed International journal

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

JOURNAL OF MATERIALS CHEMISTRY C Vol. 1 ( 36 ) page： 5741 - 5746 2013

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

A novel phosphate raw material having an oligomeric structure with desirable stability and solubility under aqueous conditions was prepared via an esterification reaction between H3PO4 and ethylene glycol under reflux. A blue emitting KSrPO4:Eu2+ phosphor with high luminescence was subsequently synthesized using a polymerizable complex (PC) method with the prepared phosphate oligomers as a source of P. KSrPO4:Eu2+ thus prepared exhibited higher emission intensity than samples prepared using a solid state reaction method or the PC method using H3PO4. This high luminescence was attributed to the excellent homogeneity of the constituents in the sample. It was found that KSrPO4 doped with more than 3 mol% of Eu2+ showed a new low-energy emission band at approximately 480 nm, in addition to the known emission band at 428 nm. This new feature was speculated to be derived from disordering of K and Sr ions caused by the high homogeneity of the constituents. Moreover, it was confirmed that thermal quenching of emission at 428 nm above 423 K was recovered in samples doped with more than 7% of Eu.

DOI： 10.1039/c3tc31121j

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Photocatalytic activities of Cu_3xLa_1-xTa₇O₁₇ solid solutions for H₂ evolution under visible light irradiation Reviewed International journal

Hideki Kato, Arisa Takeda, Makoto Kobayashi, Michikazu Hara, Masato Kakihana

Catalysis Science & Technology Vol. 3 ( 12 ) page： 3147 - 3154 2013

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

Development of new visible-light-driven oxide photocatalysts for H2 evolution was conducted with a concept of formation of solid solutions containing Cu(I) ions. Band gaps of Cu3xLa1-xTa7O19 solid solutions were 2.57-2.71 eV being remarkably narrower than that of LaTa7O19 (x = 0, 4.14 eV). The remarkable narrowing of the band gaps was due to the contribution of Cu 3d orbitals to valence bands. The solid solutions were capable of photocatalytic H-2 evolution under visible light irradiation in the presence of methanol as an electron donor. Interestingly, the solid solutions with x = 0.2-0.8 showed higher activities than that of a native Cu(I)-tantalate, Cu3Ta7O19 (x = 0). Among the solid solutions, the x = 0.6 sample, Cu1.8La0.4Ta7O19, exhibited the highest activity. The apparent quantum yield of the optimized photocatalyst was 0.48% at 420 nm. Moreover, the good stability of Cu(I) ions in the solid solutions was proven through the investigation of photocatalytic properties and the XPS analysis. Thus, new visible-light-driven oxide photocatalysts capable of H-2 evolution were developed by the formation of the Cu(3x)La(1-x)Ta(7)O19 solid solutions.

DOI： 10.1039/c3cy00557g

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Orange emission from (Ba1-XSrX)4Al 2S7:Eu2+ thioaluminate phosphors with visible light excitation Reviewed International journal

Takahiko Hasegawa, Hideki Kato, Yuji Takatsuka, Makoto Kobayashi, Hisanori Yamane, Masato Kakihana

ECS Journal of Solid State Science and Technology Vol. 2 ( 2 ) page： R3107 - R3111 2013

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

Solid solutions of (Ba1-XSrX)4Al 2S7 (X = 0.2 to 0.6) novel thioaluminate compound were synthesized, whose crystal structure was determined. The crystal structure of the (Ba1-XSrX)4Al2S7 solid solution is related to that of monoclinic Ba4Ga 2S7 consisting of isolated Ga2S7 units. However, the local structures around Ba/Sr in (Ba1-XSr X)4Al2S7, such as coordination number and one unusually long bond (d(Ba,Sr)-S 4 Å) in 7- and 8-coordinated (Ba,Sr)-S, are different from those in Ba4Ga 2S7. Eu2+-activated (Ba1-XSr X)4Al2S7 exhibited orange emission with a peak maximum at 594 nm and a corresponding excitation band at 300 to 550 nm. This is the first report of an orange phosphor in the thioaluminate system. The thermal quenching of luminescence in the (Ba1-XSr X)4Al2S7:Eu2+ phosphor was comparable to that in a conventional Y3Al5O 12:Ce3+ phosphor. © 2012 The Electrochemical Society.

DOI： 10.1149/2.019302jss

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Fabrication of SrTiO3 exposing characteristic facets using molten salt flux and improvement of photocatalytic activity for water splitting Reviewed International journal

Hideki Kato, Makoto Kobayashi, Michikazu Hara, Masato Kakihana

CATALYSIS SCIENCE & TECHNOLOGY Vol. 3 ( 7 ) page： 1733 - 1738 2013

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

Flux treatment using various molten salts was performed for SrTiO3 powders. Morphology of SrTiO3 crystals obtained by the flux treatment strongly depended on the kinds of molten salts used. Large cubic crystals exposing {100} facets with a size of 5-6 mm were obtained by the flux treatment with LiCl whereas truncated cubes exposing {100} and {110} facets with a size of 200-400 nm were obtained when NaCl or SrCl2 was used as a flux reagent. In contrast, the flux treatment with KCl gave characteristic shaped crystals with a size of 300 nm. Electron microscope observation and electron diffraction analysis revealed that the crystals treated with the KCl flux expose {100}, {120}, and {121} facets. SrTiO3 treated with the KCl flux exhibited higher activity by 20 times than the non-flux-treated sample. Thus, a remarkable improvement of activity has been achieved by the fabrication of SrTiO3 crystals exposing high-index facets, {120} and {121}, using the KCl flux.

DOI： 10.1039/c3cy00014a

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Synthesis of spindle and square bipyramid-shaped anatase-type titanium dioxide crystals by a solvothermal method using ethylenediamine Reviewed International journal

Makoto Kobayashi, Hideki Kato, Masato Kakihana

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 120 ( 1407 ) page： 494 - 499 2012.11

Language：English Publishing type：Research paper (scientific journal) Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI

Morphological control as well as formation of nanoparticles of anatase-type titanium dioxide has been achieved by a solvothermal treatment of a water-soluble citratoperoxotitanium (CPT) complex using ethylenediamine (EDA) as a key solvent in the presence of a given amount of water. When the EDA concentration in the whole solvent (EDA + H2O) remained low less than 12 M, the powder obtained after the solvothermal treatment consisted of spindle-like anatase particles. With an increase of the EDA concentration in the solvent, the shape of the obtained particles changed from spindle to square bipyramid. When another water-soluble oxoglycolatoperoxotitanate complex or TiCl4 was used as a starting source of Ti, similar shaped anatase particles could be obtained by a careful choice of synthetic conditions. Using a mixed solvent of EDA and water, sheet-like titanic acid was produced as an intermediate phase, regardless of the EDA concentration. Therefore, the formation of anatase in the current system may take place through dissolution-recrystallization of titanic acid. The formation of square bipyramidal anatase particle achieved in the present study is not agreement with a reported theoretical calculation of equilibrium phase, because the calculation reveals that truncated square bipyramid-like anatase is obtained under an acidic condition and spindle-like anatase was formed under a basic condition. An adsorption of EDA on particle surface and the pH of the solvent may contribute to the achievement of morphological control. (C)2012 The Ceramic Society of Japan All rights reserved.

DOI： 10.2109/jcersj2.120.494

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Synthesis of new thioaluminate phosphors (Ba_1-XSr_X)₄Al₂S₇:Eu and their luminescence properties Reviewed

Takahiko Hasegawa, Makoto Kobayashi, Hideki Kato, Hisanori Yamane, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display page： 640-641 2012.8

Impact of synthesis methodology on the optimization of photoluminescence emission intensity of NaBaScSi₂O₇:Eu²⁺ phosphor Reviewed International journal

Sudeshna Ray, Kenji Toda, Shinnosuke Kamei, Tadashi Ishigaki, Kazuyoshi Uematsu, Mineo Sato, Hideki Kato, Makoto Kobayashi, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display page： 128 - 129 2012.8

Synthesis of the new compound in a Na-Sc-Si-O system and Luminescence properties activated by Eu²⁺ Reviewed International journal

Jihong Min, Hideki Kato, Makoto Kobayashi, Hisanori Yamane, Masato Kakihana

Technical digest of the 12th International Meeting on Information Display page： 638-639 2012.8

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Papers - KOBAYASHI Makoto