Faculty Profiles - KOBAYASHI Makoto

酸化チタン多形の水熱結晶成長（Crystal Growth of Titania Polymorphs by Hydrothermal Method） Reviewed Open Access

小林亮

結晶成長学会誌 Vol. 42 page： 283 - 289 2015

水に分散可能な無機Siクラスター活用した水溶液プロセスによるケイ酸塩蛍光体の合成 Reviewed Open Access

小林亮, 垣花眞人

粉体および粉末冶金 Vol. 62 page： 127 - 133 2015

A carbon modified NaTaO<inf>3</inf> mesocrystal nanoparticle with excellent efficiency of visible light induced photocatalysis Reviewed International journal

Xiaoyong Wu, Shu Yin, Bin Liu, Makoto Kobayashi, Masato Kakihana, Tsugio Sato

Journal of Materials Chemistry A Vol. 2 ( 48 ) page： 20832 - 20840 2014.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry

A carbon modified NaTaO&lt
inf&gt
3&lt
/inf&gt
mesocrystal nanoparticle (ca. 20 nm) was successfully synthesized by a one-pot solvothermal method, employing TaCl&lt
inf&gt
5&lt
/inf&gt
and NaOH as the starting materials and distilled water/EG mixed solution as a reaction solvent in the presence of appropriate amounts of glucose. The mesocrystal sample presented a high specific surface area 90.8 m&lt
sup&gt
2&lt
/sup&gt
g&lt
sup&gt
-1&lt
/sup&gt
with large amounts of well-dispersed mesopores in the particle, owing to the co-effect of EG and glucose during the reaction process. A non-classic mechanism of formation was proposed for the growth of the NaTaO&lt
inf&gt
3&lt
/inf&gt
mesocrystal. Furthermore, the NaTaO&lt
inf&gt
3&lt
/inf&gt
mesocrystal exhibited considerably improved visible light absorption in addition to the intrinsic UV light absorption as a result of carbon modification originated from glucose. On the basis of the large specific surface area, high crystallinity and optical property, the carbon modified NaTaO&lt
inf&gt
3&lt
/inf&gt
mesocrystal demonstrated excellent efficiency for continuous NO gas destruction under irradiation of UV, short wavelength visible lights (&gt
400 m) and even long wavelength visible light (&gt
510 nm), considerably superior to those of the unmodified NaTaO&lt
inf&gt
3&lt
/inf&gt
specimen and commercial titania, P25. The carbon modified NaTaO&lt
inf&gt
3&lt
/inf&gt
mesocrystal nanoparticles prepared in this work would probably have potential utilization in environmental purification and energy conversion.

DOI： 10.1039/c4ta04132a

Development of two novel Eu2+-activated phosphors in the Na-Sc-Si-O system and their photoluminescence properties Reviewed International journal

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

JOURNAL OF LUMINESCENCE Vol. 154 page： 285 - 289 2014.10

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

Two novel Eu2+-activated phosphors in the Na-Sc-Si-O system were developed in this study, NaScSi2O6:Eu and Na3ScSi3O9:Eu. NaScSi2O6:Eu2+ showed yellow emission with a peak at 555 nm under excitation at 220-430 nm. When flux-treatment was performed for NaScSi2O6:Eu2+, we found the existence of a new phase. We then succeeded in synthesis of a high-purity sample of this new compound by a parallel solution synthesis method. It was revealed that the new phase was Na3ScSi3O9 with isostructure to Na3YSi3O9, and Eu2+-activated Na3ScSi3O9 exhibited photoluminescence. Na3ScSi3O9:Eu showed green emission with a peak at 530 nm and a corresponding broad excitation band up to 500 nm. However, photoluminescence of Eu2+ was negligible for Na3YSi3O9:Eu because of the stabilization of Eu3+ at the Y3+ site. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2014.05.006

Synthesis of (Ca1-xSrx)(4)Si2O7F2 oxyfluoride solid solutions and their photoluminescence properties activated by Eu2+ ions Reviewed International journal Open Access

Jihong Min, Hideki Kato, Makoto Kobayashi, Yasushi Sato, Masato Kakihana

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 122 ( 1428 ) page： 630 - 633 2014.8

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

The synthesis of oxyfluoride solid solutions with the composition (Ca1−xSrx)4Si2O7F2 is reported in this study. (Ca1−xSrx)4Si2O7F2 is found to form a solid solution within the entire composition range. Synthesis of Sr4Si2O7F2, which is the first compound in the Sr–Si–O–F system, can be regarded as one of the interesting results of this study. The Eu2+-activated (Ca1−xSrx)4Si2O7F2 solid solutions, except for Sr4Si2O7F2 exhibited photoluminescence under excitation at 300–450 nm at room temperature. The samples with x = 0.25–0.75 showed a broad red emission band with a peak around 630 nm, whereas the Ca4Si2O7F2:Eu2+ (x = 0) showed blue emission with a peak at 470 nm. Thus, the substitution of Sr for Ca in Ca4SiO7F2:Eu2+ changed the photoluminescence properties remarkably.

DOI： 10.2109/jcersj2.122.630

The significance of phosphate source in the preparation of functional luminescent phosphate materials Reviewed International journal Open Access

Minsung Kim, Makoto Kobayashi, Hideki Kato, Masato Kakihana

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN Vol. 122 ( 1428 ) page： 626 - 629 2014.8

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

The stability and reactivity of phosphate raw materials, including two water-soluble phosphates, ethylene glycol-conjugated phosphate (EG-P), and polyethylene glycol-conjugated phosphate (PEG-P) developed by our group, were examined with the aim of synthesizing phosphates with high functionalities. EG-P was found to gradually hydrolyze in an aqueous solution, resulting in the formation of H3PO4, while PEG-P was stable for more than two months. EG-P and PEG-P did not form insoluble materials in aqueous solution in the presence of many other cations, while precipitates were often observed using conventional phosphate raw materials. In particular, there were no precipitates in an aqueous solution of PEG-P in the presence of Ca2+ and Li+ ions, which easily formed insoluble phosphates in a given aqueous condition. Consequently, single-phase LiCaPO4 with high luminescence properties could be obtained by a polymerizable complex method employing PEG-P, while impurity phases were formed using other P sources, and KSrPO4 was formed as a single phase using EG-P and PEG-P.

DOI： 10.2109/jcersj2.122.626

Tailoring of deep-red luminescence in Ca2SiO4:Eu(2+). Reviewed International journal

Yasushi Sato, Hideki Kato, Makoto Kobayashi, Takaki Masaki, Dae-Ho Yoon, Masato Kakihana

Angewandte Chemie (International ed. in English) Vol. 53 ( 30 ) page： 7756 - 9 2014.7

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

We report a new dicalcium silicate phosphor, Ca(2-x)Eu(x)SiO4, which emits red light in response to blue-light excitation. When excited at 450 nm, deep-red emission at 650 nm was clearly observed in Ca1.2Eu0.8SiO4, the external and internal quantum efficiencies of which were 44 % and 50 %, respectively. The red emission from Ca(2-x)Eu(x)SiO4 was strongly related to the peculiar coordination environments of Eu(2+) in two types of Ca sites. The red-emitting Ca2SiO4:Eu(2+) phosphors are promising materials for next-generation, white-light-emitting diode applications.

DOI： 10.1002/anie.201402520

Photoluminescence properties of dee-red emitting Ca2SiO4 International journal

Y. Sato, H. Kato, M. Kobayashi, M. Kakihana

Rare Earths Vol. 64 page： 122 - 123 2014.5

Insights into a selective synthesis of anatase, rutile, and brookite-type titanium dioxides by a hydrothermal treatment of titanium complexes Reviewed International journal

Mitsuru Yoshizawa, Makoto Kobayashi, Valery Petrykin, Hideki Kato, Masato Kakihana

JOURNAL OF MATERIALS RESEARCH Vol. 29 ( 1 ) page： 90 - 97 2014.1

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

Novel water-soluble titanium complexes coordinated by hydroxycarboxylic acids or amines were developed, and the hydrothermal treatment of the new complexes was carried out to elucidate the formation mechanism of the titania polymorphs including rutile, anatase, and brookite. An empirical relationship among the crystal structure of TiO2, the ligand, and the complex structure was found. Anatase, rutile, or a mixture of both was obtained by the hydrothermal treatment of the complexes coordinated by hydroxycarboxylic acids. The structure of complexes prepared using hydroxycarboxylic acids, which have one hydroxyl and one carboxylic groups, seems to be preferable for the formation of rutile. It was also found that the hydrothermal treatment of titanium complexes coordinated by amine with NAc2 structure resulted in the formation of brookite. Thus, the effect of ligand and complex structure on the crystal structure of TiO2 synthesized by the hydrothermal treatment of the complexes was proposed.

DOI： 10.1557/jmr.2013.229

Hydrothermal synthesis of magnetite particles with uncommon crystal facets Reviewed International journal Open Access

Junki Sato, Makoto Kobayashi, Hideki Kato, Takamichi Miyazaki, Masato Kakihana

Journal of Asian Ceramic Societies Vol. 2 ( 3 ) page： 258 - 262 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.

Hydrothermal synthesis of Fe3O4 (magnetite) particles was carried out using organic compounds as morphology control agents to obtain magnetite crystals with uncommon facets. It was established that the morphology of Fe3O4 crystals obtained by hydrothermal treatment of an aqueous solution containing Fe2+ and organic compounds depended on the organic compound used. The shape of the Fe3O4 particles obtained when no additives were used was quasi-octahedral. In contrast, the addition of picolinic acid, citric acid or pyridine resulted in the formation of polyhedral crystals, indicating the presence of not only {111}, {100} and {110} facets but also high-index facets including at least {311} and {331}. When citric acid was used as an additive, octahedral crystals with {111} facets also appeared, and their size decreased as the amount of citric acid was increased. Thus, control of Fe3O4 particle morphology was achieved by a simple hydrothermal treatment using additives. © 2014 The Ceramic Society of Japan and the Korean Ceramic Society.

DOI： 10.1016/j.jascer.2014.05.008

Open Access