Shuhei Yamada

Kyushu Institute of Technology, Kitakyūshū, Fukuoka, Japan

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Publications (6)16.98 Total impact

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    ABSTRACT: It is highly desirable to develop controlled synthetic methods at low temperature (<100°C) for defined phases of titanium oxide nanoparticle. We present here a simple low temperature approach which is based on the peroxide route. This approach allows the preparation of phase-pure rutile and anatase without the use of any additives or surfactants or external acids. The formation of crystalline phases is found to be dependent on reaction temperature and highly dependent on concentration. Phase-pure rutile is obtained in two concentration zones while phase-pure anatase is obtained in one concentration zone. The relationship between phases and reaction conditions (concentration and temperature) fits well with the nucleation diffusion rate model. Copyright © 2015 Elsevier Inc. All rights reserved.
    Journal of Colloid and Interface Science 02/2015; 448C. DOI:10.1016/j.jcis.2015.02.001 · 3.55 Impact Factor
  • Shuhei Yamada, Emiko Mouri, Kohji Yoshinaga
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    ABSTRACT: We report a novel strategy for incorporation of titanium dioxide (TiO2) particles into poly(methyl methacrylate) (PMMA) to exploit high refractive and transparent organic–inorganic hybrid materials. Formation of TiO2 particles of around 20 nm was conducted within hydrophilic core of block copolymer micelles of poly(methyl methacrylate-block-acrylic acid) (PMMA-b-PAA) in toluene via sol–gel process from titanium isopropoxide and hydrochloric acid. Subsequently, incorporation of TiO2 particles into PMMA matrix was carried out by casting toluene solution of TiO2 precursor-loaded copolymer micelles, prepared from PMMA350-b-PAA93 and the precursor of mole ratio Ti4+/carboxyl 4.0, and PMMA. Hybrid films of TiO2/PMMA exhibited high transparency to achieve transmission over 87% at 500 nm at 30 wt % of TiO2 content. The refractive index of resulting hybrid films at 633 nm linearly increased with TiO2 content to attain 1.579 at 30 wt % TiO2, which was 0.1 higher than that of PMMA. Cross-sectional transmission electron microscope images of TiO2/PMMA hybrid films showed existence of TiO2 clusters less than 100 nm, which were probably formed by aggregation or agglutination of TiO2 particles during a drying process. It was also observed that decomposition temperature of the hybrid films elevated with increasing TiO2 content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
    Journal of Polymer Science Part A Polymer Chemistry 02/2011; 49(3):712 - 718. DOI:10.1002/pola.24483 · 3.54 Impact Factor
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    ABSTRACT: We report the synthesis and characterization of new series of the fluorene based polymers with carbazole and oxadiazole pendants for the generation of the white emission out of the EL device. In the fluorene backbone, hole transporting units such as carbazole or phenothiazine were incorporated to improve the EL brightness and efficiency. The PFCzOxd-co-PCzs and PFCzOxd-co-PPTZs in EL spectra showed maximum peaks at around 430 nm and additional large peaks at around 530 and 500 nm, respectively. In case of PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz, the EL spectra of the polymers showed two distinct peaks comprising the maximum at 427 nm, which corresponds to the EL spectra of the conjugated backbone, and additional broad peaks at around 540 and 530 nm, respectively. The CIE coordinates of the devices from PFCzOxd-alt-PCz and PFCzCzPCz-co-PFOxdOxdPCz were (0.28, 0.33) and (0.25, 0.32), respectively, approaching the value of the standard white of National Television System Committee (NTSC) (0.33, 0.33).
    Polymer 12/2010; 51(26):6174-6181. DOI:10.1016/j.polymer.2010.10.061 · 3.77 Impact Factor
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    ABSTRACT: Crystallization of TiO2 particles from peroxytatanic acid in the presence of poly(vinyl alcohol) (PVA) via a hydrothermal process was investigated. The crystal structure and morphology of TiO2 were significantly affected by pH and PVA dosage. High acidic condition without PVA led to the formation of rutile TiO2, while addition of PVA resulted in the formation of anatase TiO2. Much amount of PVA addition, and neutral or high pH circumstance were favorable for formation of anatase TiO2 particles. The pH of solution also affected morphology of TiO2 particles produced. From TEM images, it was observed that in pH 5.5 solution rod-shaped clusters and in pH 8.5 solution nanoparticles aggregates composed of 20–30nm TiO2 particles were formed.
    Colloid and Polymer Science 01/2010; 288(4):433-438. DOI:10.1007/s00396-009-2141-x · 2.41 Impact Factor
  • Shuhei Yamada, Zhifeng Wang, Kohji Yoshinaga
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    ABSTRACT: Tiatanium dioxide (TiO2) nanoparticles, of around 20 nm in diameter, were synthesized within the hydrophilic core of micelles, formed using poly(acrylic acid-block-methyl methacrylate) in toluene solution, via sol-gel process using titanium isopropoxide. Hybrid films of poly(methyl methacrylate) (PMMA) containing TiO2 nanoparticles exhibit high transparency in the visible light region even at 30 wt % TiO2. The refractive index of the hybrid films at 633 nm linearly increased with TiO2 to attain 1.579.
    Chemistry Letters 08/2009; 38(8):828-829. DOI:10.1246/cl.2009.828 · 1.30 Impact Factor
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    ABSTRACT: We report a novel strategy for incorporation of titanium dioxide (TiO2) particles, which were crystallized from peroxotitanic acid in the presence of hydrophilic polymer by hydrothermal treatment in aqueous solution, into poly(methyl methacrylate) (PMMA) via dispersion into chloroform. Dispersion of TiO2 particles into chloroform was achieved by solvent change from water to chloroform in aid of amphiphilic polymer dispersant, poly(N-vinyl pyrrolidone) (PVP), poly(N-vinyl pyrrolidone-co-methyl methacrylate) (PVP-co-PMMA), poly(N-vinyl pyrrolidone-block-methyl methacrylate) (PVP-b-PMMA) through azeotropical removal of water. Incorporation of TiO2 particles into PMMA was carried out by a casting process of a mixture of TiO2 particles dispersed with PVP154-b-PMMA156 in chloroform and PMMA on a glass substrate. Resultant hybrid film containing TiO2 less than 10wt.% showed high transparency in visible region attributable to homogeneous dispersion into PMMA matrix. The refractive index of the hybrid films increased with TiO2 content and agreed with the calculated values.
    Colloid and Polymer Science 02/2008; 287(2):139-146. DOI:10.1007/s00396-008-1957-0 · 2.41 Impact Factor