Faculty Profiles - KOBAYASHI Makoto

Morphology-Controlled Synthesis of W₁₈O₄₉ Nanostructures and Their Near-Infrared Absorption Properties Reviewed International journal

Chongshen Guo, Shu Yin, Mei Yan, Makoto Kobayashi, Masato Kakihana, Tsugio Sato

Inorganic chemistry Vol. 51 ( 8 ) page： 4763 - 71 2012.4

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

The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W(18)O(49) were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W(18)O(49), such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl(6), W(EtO)(6), and WO(3) solids as the tungsten source. W(18)O(49) nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W(18)O(49) nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.

DOI： 10.1021/ic300049j

PubMed

Hydrothermal synthesis of brookite-type titanium dioxide with snowflake-like nanostructures using a water-soluble citratoperoxotitanate complex Reviewed International journal

Makoto Kobayashi, Valery Petrykin, Koji Tomita, Masato Kakihana

Journal of Crystal Growth Vol. 337 ( 1 ) page： 30 - 37 2011.12

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

Hydrothermal synthesis of brookite-type titanium dioxide was performed with excellent reproducibility using an aqueous NH3 solution of a water-soluble citratoperoxotitanate (CPT) complex. X-ray diffraction confirmed that the brookite phase was formed by hydrothermal treatment of the CPT complex in NH3 solution with a concentration of more than 6.5 wt%, whereas single phase anatase was obtained when distilled water without any additives was applied as the solvent. The aspect ratios of the obtained rod-like brookite particles increased from 5 up to 20 with an increase of the NH3 concentration. Transmission electron microscopy and selected area electron diffraction measurements provided evidence that the growth of the brookite particles is along the c-axis. Hydrothermal treatment of the CPT complex at high NH3 concentrations resulted in the formation of agglomerated brookite particles with unusual shapes, where many rod-like particles were branched around a somewhat longer central particle, and the side view of the agglomerated particles revealed two-dimensional crystal growth within a given restricted plane. The multi-needle agglomerate of particles was snowflake shaped. The reason for the formation of brookite with this unique morphology may be attributed to an intrinsic character of the CPT complex itself, although the mechanism is yet to be clarified. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2011.09.046

Hydrothermal synthesis of hierarchical TiO₂ microspheres using a novel titanium complex coordinated by picolinic acid Reviewed International journal

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

Journal of the Ceramic Society of Japan Vol. 119 ( 1390 ) page： 513 - 516 2011

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

Phase- and morphology-control of TiO2 was performed by a facile hydrothermal method using a novel water-soluble titaniumpicolinato complex as a precursor. Single-phase rutile or brookite type titania can be obtained by tailoring the pH of the complex solution. Rutile with a hierarchical microstructure was synthesized using an excess amount of ligand as an additive and the final product consisted of microspheres with mesopores formed by a self-assembly of nanorods. The anisotropic growth of nanorods with a high aspect ratio was explained by a capping mechanism. © 2011 The Ceramic Society of Japan.

DOI： 10.2109/jcersj2.119.513

Application of Water-Soluble Titanium Complexes as Precursors for Synthesis of Titanium-Containing Oxides via Aqueous Solution Processes Invited Reviewed International journal

Masato Kakihana, Makoto Kobayashi, Koji Tomita, Valery Petrykin

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 83 ( 11 ) page： 1285 - 1308 2010.11

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

The growing significance of nanocrystalline inorganic functional materials in the fields of catalysis, electronics, and energy conversion together with the increasing demand of the society for safer, softer, and "greener" technologies has drawn considerable attention of the researchers toward water-based solution processes for synthesis of such materials. In this respect complex oxides, containing d(0)-transition metals, such as Ti, Nb, Ta, or Si represent an outstanding challenge. for materials chemists due to the extremely narrow range or almost complete absence of suitable precursor compounds compatible with aqueous systems. In the recent 10 years, a remarkable progress has been achieved in the development of new water-soluble complexes of titanium and considerable experience was accumulated in the application of these compounds for synthesis of nanocrystalline titanium-containing materials. The essential knowledge of coordination chemistry of such water-soluble titanium complexes is reviewed in this work, which succeeded to identify the key structural features responsible for stability of the compounds against hydrolysis and to provide guidelines for synthesis of these complexes. Finally, an extensive overview of highly selective aqueous solution based synthesis of TiO2 polymorphs as well as complex oxide materials with the help of the novel water-soluble titanium complexes is provided.

DOI： 10.1246/bcsj.20100103

酸化チタンのテーラメイド合成 Invited Reviewed

小林亮, 垣花眞人

現代化学 Vol. 465 ( 12 ) page： 57-62 2009.11

Selective Synthesis of TiO2 Polymorphs by Hydrothermal Method using New Water-Soluble Titanium Complexes Invited Reviewed International journal

Masato Kakihana, Makoto Kobayashi, Valery Petrykin, Koji Tomita

Journal of the Japan Society of Powder and Powder Metallurgy Vol. 56 ( 4 ) page： 188-193 2009.4

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

A panel of new stable and water soluble complexes of titanium (IV) with natural hydroxy-carboxylic acids such as citric, tartaric, lactic or glycolic acid as ligands was developed. A typical structure of these complex ions includes a peroxo-group, and a hydroxy-carboxylic acid molecule attached to the metal ion by carboxylic and hydroxylic groups to form stable species. The tight coordination and negative charge of complex ions are responsible for stability of these new compounds in water solutions in a wide range of temperatures and pH. Use of natural non-toxic ligands and ammonium as counterions make such titanium compounds convenient reagents for "green" synthesis of titanium containing materials by aqueous solution methods. The architecture of titanium complexes includes structural motifs of different polymorphic forms of TiO2, which allows for application of these compounds as building blocks (tecton) for synthesis of titania with different crystal structures by a simple hydrothermal processes. In this way anatase, rutile, TiO2(B) and brookite were prepared in a reproducible and highly selective way. For the first time TiO2(B) and brookite were synthesized as single phase nano-crystals by a "one-pot" hydrothermal process, and their outstanding photo-catalytic activities were revealed.

DOI： 10.2497/jjspm.56.188

Hydrothermal synthesis of brookite type TiO2 photocatalysts using a water-soluble Ti-complex coordinated by ethylenediaminetetraacetic acid Reviewed International journal

Yusuke Morishima, Makoto Kobayashi, Valery Petrykin, Shu Yin, Tsugio Sato, Masato Kakihana, Koji Tomita

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 117 ( 1363 ) page： 320 - 325 2009.3

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

Nanocrystalline brookite titanium oxide was prepared by hydrothermal treatment of a water-soluble titanium complex with ethylenediaminetetraacetic acid (EDTA). In this work, we examined the effect of synthesis conditions such as reaction time, titanium concentration and solution pH on the brookite phase formation and its photocatalyitic performance. It was found that hydrothermal treatment of the titanium complex may yield anatase and brookite phases, and their ratio can be varied depending on titanium concentration. Single phase brookite could be prepared when titanium concentration in the starting solution was higher than 0.25 mol/dm(3), while lower concentration favors formation of anatase. Remarkably, brookite could be synthesized from the Ti-EDTA complex in the wide range of pH including both acidic and basic media. The samples prepared from Ti-EDTA complex demonstrated higher photocatalytic activity in terms of NO gas decomposition than the brookite powders synthesized from Ti-glycolate complex or commercial TiO2 photocatalyst P25. Higher photocatalytic activity of powders obtained from Ti-EDTA complex aqueous solution is explained by higher surface area of smaller but well-crystallized brookite particles that can be achieved when this new titanium complex is employed. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.320

Photocatalytic activity of nanocrystalline TiO2(B) synthesized from titanium glycolate complex by hydrothermal method Reviewed International journal

Kazuhiro Yamamoto, Hironori Shimoita, Koji Tomita, Kazumi Fujita, Makoto Kobayashi, Valery Petrykin, Masato Kakihana

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 117 ( 1363 ) page： 347 - 350 2009.3

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

The metastable phase of TiO2(B), one of the polymorphs of titanium dioxide (TiO2), was prepared by a hydrothermal treatment of a titanium glycolate complex ([Ti-4(C2H2O3)(4)(C2H3O3)(2)(O-2)(4)O-2](6-)) at 473 K for 1-72 h in the presence of H2SO4. Characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the obtained samples were composed of single phase TiO2(B) and the particles had plate-like morphology. After post-synthetic hydrothermal crystal growth (PHCG) applied to the as-prepared sample, thicker plate-like shaped particles were obtained. The photocatalytic activities of the samples obtained by the hydrothermal treatment and after the subsequent PHCG were evaluated in terms of methanol decomposition. (C) 2009 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.117.347

チタン錯体水溶液からの酸化チタン光触媒の合成 Invited Reviewed

小林亮, Petykin Valery, 垣花眞人, 冨田恒之

化学工業 Vol. 60 ( 1 ) page： 71-77 2009.1

Hydrothermal Synthesis and Photocatalytic Activity of Whisker-Like Rutile-Type Titanium Dioxide Reviewed International journal

Makoto Kobayashi, Valery Petrykin, Masato Kakihana, Koji Tomita

JOURNAL OF THE AMERICAN CERAMIC SOCIETY Vol. 92 ( 1 ) page： S21 - S26 2009.1

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-BLACKWELL PUBLISHING, INC

Nanowhiskers of rutile-type titanium dioxide (TiO(2)) were synthesized by a simple hydrothermal treatment of a water-soluble titanium-glycolate complex at 473 K. The aspect ratio of the obtained rutile particles could be controlled by changing the concentration of the glycolic acid additive in the starting aqueous solution of the titanium complex. According to high-resolution transmission electron microscopy, whisker-like nanoparticles grow along the c-axis of rutile, the side facets of which are (110), (-110), (1-10), and (-1-10). Glycolic acid controls promotion of the rutile particles in the specified direction due to its preferred adsorption on the titanium-rich facets. Evaluation of the photocatalytic activity of the synthesized TiO(2) was performed in terms of decomposition of oxalic acid in an aqueous system under ultraviolet irradiation. It turned out that this particular whisker-like shape is responsible for the tremendous enhancement of rutile photocatalytic activity, and even rutile samples with low surface area demonstrated photocatalytic performance comparable with one of the best nanosized anatase photocatalytic materials. Therefore, it can be concluded that the (110) rutile facet plays an important role in the photocatalytic oxidation reaction, and that it exhibits higher photocatalytic activity than the (001) facet in the decomposition of oxalic acid.

DOI： 10.1111/j.1551-2916.2008.02641.x

Synthesis of TiO2(B) using glycolato titanium complex and post-synthetic hydrothermal crystal growth of TiO2(B) Reviewed International journal

K. Yamamoto, K. Tomita, K. Fujita, M. Kobayashi, V. Petrykin, M. Kakihana

Journal of Crystal Growth Vol. 311 ( 3 ) page： 619 - 622 2009.1

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

Titanium dioxide (TiO2(B), one of metastable polymorphs of TiO2 was prepared by hydrothermal reaction of glycolato peroxotitanium complex ([Ti-4(C2H2O3)(4)(C2H3O3)(2)(O-2)(2)](6) in the presence of H2SO4 as an additive. Characterization by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) revealed that the obtained powders were single-phase TiO2(B) with rod-like shape, Particle size and aspect ratio of TiO2(B) can be controlled by post-synthetic hydrothermal crystal growth (PHCG) of the as-prepared powder sample. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2008.09.041

Selective synthesis of nano-crystalline TiO₂ polymorphs from new water-soluble titanium complexes Reviewed

Masato Kakihana, Makoto Kobayashi, Valery Petrykin, Koji Tomita

Acta Crystallographica Section A ( 64 ) page： C20 2008.8

Direct synthesis of brookite-type titanium oxide by hydrothermal method using water-soluble titanium complexes Reviewed International journal

Makoto Kobayashi, Koji Tomita, Valery Petrykin, Masahiro Yoshimura, Masato Kakihana

Journal of Materials Science Vol. 43 ( 7 ) page： 2158 - 2162 2008.4

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

It was demonstrated that brookite-type titanium oxide can be directly synthesized by the hydrothermal treatment of novel water-soluble titanium complexes under basic conditions in the presence of an additive. In particular, single-phase brookite was synthesized from the titanium-glycolate complex at a pH of about 10 in the presence of excess NH(3) aqueous solution or ethylenediamine, and powder thus obtained consisted of rod-like nanosized particles. It was suggested that the structures of titanium complexes are important for the formation of brookite.

DOI： 10.1007/s10853-007-1912-3

Hydrothermal synthesis of TiO₂ nano-particles using novel water-soluble titanium complexes Reviewed International journal

Koji Tomita, Makoto Kobayashi, Valery Petrykin, Shu Yin, Tsugio Sato, Masahiro Yoshimura, Masato Kakihana

Journal of Materials Science Vol. 43 ( 7 ) page： 2217 - 2221 2008.4

Language：English Publishing type：Research paper (international conference proceedings)

Hydrothermal treatment of a series of water-soluble titanium complexes resulted in the formation of TiO2. Rutile, anatase or a mixture of both can be synthesized by varying the ligands. The titania obtained was composed of nano-sized particles with large specific surface areas. These TiO2 powders exhibited high photocatalytic activity for NO x decomposition. In particular, they demonstrated higher activity than P25 (Degussa) under visible-light irradiation. © 2007 Springer Science+Business Media, LLC.

DOI： 10.1007/s10853-007-2113-9

New water-soluble complexes of titanium with amino acids and their application for synthesis of TiO₂ nanoparticles Reviewed International journal

Makoto Kobayashi, Valery Petrykin, Koji Tomita, Masato Kakihana

Journal of the Ceramic Society of Japan Vol. 116 ( 1352 ) page： 578 - 583 2008.4

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

We prepared two new water-soluble complexes of titanium with L-serine and L(-)-threonine amino acids. It was demonstrated that these compounds can be outstanding precursors for a hydrothermal synthesis of nanocrystalline TiO2. The obtained powders were composed of anatase or a mixture of anatase and brookite. Particles diameters were -10 nm and BET surface areas were -120 m(2)/g. The powder composed of anallase and brookite synthesized by hydrothermal treatment of the titanium-threonine complex aqueous solution at 200 degrees C for 24 h exhibited higher photocatalytic activity for oxalic acid oxidation than the commercial anatase-type TiO2 photocatalyst (ST-01, Ishihara Sangyo Kaisya, average diameter: 7 nm, specific surface area: 257.5 m(2)/g). (c) 2008 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.116.578

INOR 1052-Synthesis of oxide materials using new water soluble titanium and tantalum complexes Reviewed International journal

Valery Petrykin, Makoto Kobayashi, Koji Tomita, Masato Kakihana

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 235 2008.4

Microwave-assisted hydrothermal synthesis of brookite nanoparticles from a water-soluble titanium complex and their photocatalytic activity Reviewed International journal

Yusuke Morishinia, Makoto Kobayashi, Valery Petrykin, Masato Kakihana, Koji Tomita

Journal of the Ceramic Society of Japan Vol. 115 ( 1348 ) page： 826 - 830 2007.12

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

Nanoparticles of brookite titanium oxide were prepared by microwave-assisted hydrothermal (MH) method at 200 degrees C (heating time 5 min) for 0-60 minutes starting from the titanium peroxo glycolate complex in basic solution. The effect of microwave heating on the morphology of the brookite particles was examined. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM). It was found that all powders were composed of single phase brookite and contained two different types of particles. The activity in photodecomposition of oxalic acid by the samples prepared using MH method was higher than activities of brookite nanoparticles synthesized by the conventional hydrothermal method.

DOI： 10.2109/jcersj2.115.826