Papers - SAKAI Go
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Matsunaga Naoki, Waseda Kousei, Kuroki Masato, Nomura Kouki, Sakai Go
54 1 - 5 2025.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Faculty of Engineering, University of Miyazaki
DOI： 10.34481/0002001934
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Matsunaga N., Kikuchi K., Tokunaga K., Kohno D., Sakai G.
Bulletin of Materials Science 46 ( 3 ) 2023.9
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Bulletin of Materials Science
The present study was conducted to prepare precursors by rapid hydrolysis method for realizing lower temperature formation of NiFe2O4 under hydrothermal conditions. The precursor, obtained from a lower concentration of NiCl2–FeCl2 mixed solution, was almost amorphous and could be easily converted to NiFe2O4 crystal phase at around 130°C by hydrothermal treatment. On the other hand, when a higher concentration of NiCl2–FeCl2 solution or trivalent iron salt (FeCl3) was used as starting reagents, individual crystal phases such as α-Ni(OH)2, γ-Fe2O3 and α-FeOOH were recognized in precursors owing to the difference in hydrolysis rates between Ni2+ and Fe2+ (or Fe3+). These individual crystal phases involved precursors that could not be converted easily to NiFe2O4 crystal phase, but needed to treat at higher temperatures for forming NiFe2O4 at least 200°C. Thus, the co-existence of individual crystal phases in precursors might prevent the amorphous precursor from forming NiFe2O4 crystal phase. The formation of NiFe2O4 at lower temperatures is considered to be taken place preferentially from amorphous precursors than individual certain crystal phases.
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Optimum dopant of barium zirconate electrolyte for manufacturing of protonic ceramic fuel cells Reviewed
Kuroha T., Niina Y., Shudo M., Sakai G., Matsunaga N., Goto T., Yamauchi K., Mikami Y., Okuyama Y.
Journal of Power Sources 506 2021.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Power Sources
We examine ceramic tape-casting and anode electrolyte co-firing for large-scale manufacturing of protonic ceramic fuel cells. We confirm the reactivity of Ni, a commonly used anode, with BaZr0.8M0.2O3−δ (BZM20: M = Sc, In, Lu, Yb, Y or Gd). Addition of 0.4 mol% NiO to BZM20 and co-firing at 1778 K, produces BaM2NiO5 for M = Y and Gd. No reaction occurs for M = Sc, In, Lu and Yb. The proton conductivity of all BZM20s decreases by approximately 30% because of NiO doping and dehydration on dissolution NiO. Energy efficiency and power density calculations of the fuel cells based on measured proton and hole conductivities indicate respective decreases of approximately 10% and 75% ecause of the formation of a solid solution of NiO. We fabricate fuel cells by the tape-casting and anode electrolyte co-firing with BZM20 (M = Yb or Y). For M = Y, the cell cannot be fabricated because formation of BaY2NiO5 causes cell cracking. Conversely, when M = Yb, a cell with a maximum output of 0.5 Wcm−2 at 873 K is fabricated. Hence, BZYb20 is a suitable material for tape-casting and anode electrolyte co-firing.
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Kuroha T., Yamauchi K., Mikami Y., Tsuji Y., Niina Y., Shudo M., Sakai G., Matsunaga N., Okuyama Y.
International Journal of Hydrogen Energy 45 ( 4 ) 3123 - 3131 2020.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Journal of Hydrogen Energy
We investigated the influence of Ni on protonic ceramic fuel cells based on indium-doped barium zirconate. A tubular fuel cell was fabricated and evaluated with BaZr0.8In0.2O3−δ as an electrolyte. The maximum power density was 0.143 W cm−2 and the ohmic resistance of the electrolyte was 0.91 Ω cm2 at 873 K. We used secondary ion mass spectrometry to measure the dissolution of Ni in the electrolyte N to be 0.015. To clarify the effect of Ni on proton transport properties of BaZr0.8In0.2O3−δ, electrical conductivity and proton concentration were measured by AC impedance analysis and thermogravimetric analysis. Electrical conductivity decreased as the NiO content increased. Conversely, proton concentration was independent of the NiO content and proton diffusivity decreased. The sample density also depended on the NiO content. The density decreased as NiO content increased. These results were consistent with the density calculated based on a model describing formation of oxygen vacancies.
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Experimental and theoretical approaches for the investigation of proton conductive characteristics of La1-xBaxYbO3-d Reviewed
Yuki Obukuro, Yuji Okuyama, Go Sakai, Shigenori Matsushima
Journal of Alloys and Compounds 770 294 - 300 2019
Language：English Publishing type：Research paper (scientific journal)
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Okuyama Yuji, Ymaguchi Takuya, Matsunaga Naoki, Sakai Go
MATERIALS TRANSACTIONS 59 ( 1 ) 14 - 18 2018
Language：English Publishing type：Research paper (scientific journal) Publisher：公益社団法人 日本金属学会
In order to clarify the effect of the dopant concentration and phase transition on the proton conduction and proton concentration, the electrical conductivity and proton concentration were determined for La<sub>1−</sub><i><sub>x</sub></i>Ba<i><sub>x</sub></i>Yb<sub>0.5</sub>In<sub>0.5</sub>O<sub>3−δ</sub> (x = 0.1. 0.3. 0.5, 0.7). The phase transition from the orthorhombic system to the cubic system was over <i>x</i> = 0.3. The proton/deuteron isotope effect on the conductivity was observed for all samples at 673 K. The proton concentration was independent of the barium content above 673 K. The proton concentration increased with the barium content below 673 K, but the concentration ratio of the proton to dopant decreased following an increase in the barium concentration. It was determined that the dopant concentration and phase transition do not have an influence on the conduction and incorporation of protons into the La<sub>1−</sub><i><sub>x</sub></i>Ba<i><sub>x</sub></i>Yb<sub>0.5</sub>In<sub>0.5</sub>O<sub>3−δ</sub>.
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A direct methane fuel cell with double-layered electrolyte using proton conducting oxide Reviewed
Okuyama Y., Kawano S., Sakai G., Matsunaga N., Mizutani Y.
ECS Transactions 78 ( 1 ) 1953 - 1961 2017.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ECS Transactions
© The Electrochemical Society. BaCe0.8Y0.2O3-δ(BCY) has high proton conductivity, but is less stable against carbon dioxide. La0.9Sr0.1Yb0.8In0.2O3-δ(LSYbIn) is chemically stable, but not as conductive as BCY. In this study, the performance of a methane fuel cell using BCY and LSYbIn as electrolytes was evaluated. The fuel cell using BCY showed shortterm degradation. On the other hand, the fuel cell using LSYbIn showed high durability using methane. The protonic ceramic fuel cell with a double-layered electrolyte was developed to improve chemical stability toward methane and the fuel cell performance. LSYbIn was used as the fuel side intermediate layer of the fuel cell using BCY for protection from methane. The fuel cell with a double-layered electrolyte suppressed the degradation by methane.
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Obukuro Y., Ninomiya K., Arai M., Okuyama Y., Sakai G., Matsushima S.
Computational Materials Science 126 7 - 11 2017.1
Language：English Publishing type：Research paper (scientific journal) Publisher：Computational Materials Science
© 2016 Elsevier B.V. The electronic structure of LaYbO 3 was investigated by the full potential linearized augmented plane wave plus local orbital (FLAPW + lo) method with the modified Becke–Johnson potential combined with the local density approximation correlation plus onsite Coulomb interaction (MBJ–LDA + U) for the sake of localized f electrons. This approach was suitable for evaluating electronic structure of LaYbO 3 system from view point of calculation cost and time. The band gap, the difference in energy between the valence band (VB) and conduction band (CB), was estimated to be 6.0 eV by the present method. The evaluated value was very close to the reported experimental value. In the VB, Yb 4f orbitals and O 2p orbitals were well hybridized each other to state predominantly. The lower potential region in CB was mainly composed of La 4f orbitals, while the upper region in CB was mainly consisted of La 5d orbitals.
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Proton-conducting oxide with redox protonation and its application to a hydrogen sensor with a self standard electrode Reviewed
Yuji Okuyama, Shinya Nagamine, Akira Nakajima, Go Sakai, Naoki Matsunaga, Fusako Takahashi, Koji Kimata, Tomoko Oshima, Koji Tsuneyoshi
RSC Advances 6 34019 - 34026 2016.3
Language：English Publishing type：Research paper (scientific journal)
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Obukuro Y., Matsushima S., Obata K., Suzuki T., Arai M., Asato E., Okuyama Y., Matsunaga N., Sakai G.
Journal of Alloys and Compounds 658 139 - 146 2016.2
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Alloys and Compounds
© 2015 Elsevier B.V. Single-phase Sr 2 Bi 2 O 5 was obtained by calcination of the heterobimetallic complex precursor Sr[Bi(DTPA)]·9H 2 O (DTPA is diethylenetriaminepentaacetic acid) at 700 °C for 6 h. The effect of La doping on the crystal structure, surface area, morphology, surface chemical state, and absorption properties of Sr 2 Bi 2 O 5 samples prepared from Sr[Bi(DTPA)]·9H 2 O were investigated. No traces of an impurity phase were detected in samples with a lower La content (3 and 5 mol%), while impurity phases such as Sr 6 Bi 2 O 9 and SrCO 3 were observed in Sr 2 Bi 2 O 5 samples with larger La contents of 8 and 10 mol%. The Brunauer-Emmett-Teller surface area of Sr 2 Bi 2 O 5 increased slightly with the content of La. High-resolution transmission electron microscopy revealed clear crystalline planes for both undoped and La-doped Sr 2 Bi 2 O 5 samples without amorphous phases. Meanwhile, X-ray photoelectron spectroscopy indicated that the valence states of constituent metals were Sr 2+ , Bi 3+ , and La 3+ . The solubility limit of La in the Sr 2 Bi 2 O 5 crystal phase was determined from Raman scattering measurements. La atoms substituted Bi sites when the doping content was low, while both Bi and Sr sites were substituted with La when the content of La was high. The electronic structure of Sr 2 Bi 2 O 5 could be modified by La doping, resulting in a red shift of the absorption edge with increasing La content. The band-gap narrowing of Sr 2 Bi 2 O 5 with La-doping was reproduced in energy-band calculations. The photocatalytic activity of Sr 2 Bi 2 O 5 under visible-light irradiation for the oxidation of isopropanol was enhanced by doping with La.
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Electronic structure of photoresponsive Ag<sub>6</sub>M<sub>2</sub>O<sub>7</sub> (M = Si, Ge) Reviewed
OBUKURO Yuki, NINOMIYA Kakeru, MATSUSHIMA Shigenori, NAKAMURA Hiroyuki, OBATA Kenji, SAKAI Go, ARAI Masao, KOBAYASHI Kenkichiro
Journal of the Ceramic Society of Japan 124 ( 1 ) 116 - 121 2016.1
Language：English Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
The electronic structures of Ag<sub>6</sub>M<sub>2</sub>O<sub>7</sub> (M = Si, Ge) are investigated by the scalar-relativistic full potential linearized augmented plane wave plus local orbital (FLAPW+lo) method using the modified Becke-Johnson (MBJ) potential combined with the local density approximation (LDA) correlation. For Ag<sub>6</sub>M<sub>2</sub>O<sub>7</sub> (M = Si, Ge), the valence band maximums (VBM) are approximately located at the X (Si) or A (Ge) and the conduction band minimums (CBM) at the Γ both, indicating that Ag<sub>6</sub>M<sub>2</sub>O<sub>7</sub> are an indirect energy gap material. The fundamental band gaps of Ag<sub>6</sub>Si<sub>2</sub>O<sub>7</sub> and Ag<sub>6</sub>Ge<sub>2</sub>O<sub>7</sub> are calculated to be 1.69 and 1.42 eV, respectively, in the MBJ-LDA calculation. The results are a remarkably contrast to the underestimation based on the generalized gradient approximation (GGA) calculation. On the other hand, there is no distinct difference in the effective masses of photogenerated holes and electrons near the VBM and CBM between MBJ-LDA and GGA approaches. The optical properties of Ag<sub>6</sub>M<sub>2</sub>O<sub>7</sub> (M = Si, Ge) are contemplated from spectral dependence of the complex dielectric function, ε (ω) = ε<sub>1</sub> (ω) + <i>i</i>ε<sub>2</sub> (ω).
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Sakai G., Tanaka A., Sueda T., Ogata T., Okuyama Y., Matsunaga N.
Chemistry Letters 45 ( 3 ) 318 - 320 2016.1
Language：English Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
© 2016 The Chemical Society of Japan. Crystal growth under hydrothermal treatment at 150 °C was observed for the pre-calcined TiO 2 -SnO 2 precursor obtained by the calcination at 250 °C. This phenomenon was observed for the trivalent titanium ion (Ti3 + ) used as the starting material for hydrolysis. The peculiar crystal growth phenomenon was thought to be originated from the oxidation of titanium from trivalent to tetravalent, because such peculiar crystal growth under hydrothermal conditions was not observed when tetravalent titanium was used.
DOI： 10.1246/cl.151106
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Okuyama Y., Nagamine S., Nakajima A., Sakai G., Matsunaga N., Takahashi F., Kimata K., Oshima T., Tsuneyoshi K.
RSC Advances 6 ( 40 ) 34019 - 34026 2016
Language：English Publishing type：Research paper (scientific journal) Publisher：RSC Advances
© The Royal Society of Chemistry 2016. In order to simplify the structure of the EMF-type hydrogen sensor using a proton conductor as the electrolyte, an electrolyte serving as a self-standard electrode in air was developed. The electrochemical properties and proton dissolution mechanism of Mn-doped CaZrO 3 were evaluated by impedance analysis, EMF measurement, IR absorption analysis and ESR measurement. Mn-doped CaZrO 3 acquires a proton from hydrogen by reduction of the manganese ion. 5 mol% Mn doped CaZrO 3 showed proton conduction in a reducing atmosphere and hole conduction in an oxidizing atmosphere. A gas concentration cell using CaZr 0.95 Mn 0.05 O 3-δ as the electrolyte was constructed for use as a hydrogen sensor. It was found to be dependent only on the hydrogen potential of the working electrode when air was used as the reference gas.
DOI： 10.1039/c5ra23560j
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CO<inf>2</inf> sensing properties of Zr-added porous CaFe<inf>2</inf>O<inf>4</inf> powder Reviewed
Obata K., Mizuta K., Obukuro Y., Sakai G., Hagiwara H., Ishihara T., Matsushima S.
Sensors and Materials 28 ( 11 ) 1157 - 1164 2016
Language：English Publishing type：Research paper (scientific journal) Publisher：Sensors and Materials
© MYU K.K. The gas sensing properties of Zr-added and pure CaFe 2 O 4 powders for CO 2 in air were examined in the temperature range of 250-450 °C. The semiconductor-type gas sensor made from pure CaFe 2 O 4 powder showed a fairly good response to CO 2 . Furthermore, the addition of a small amount of Zr into CaFe 2 O 4 powder was found to be effective for enhancing the CO 2 response of the present gas sensor. It was also found that the gas response, defined by the ratio of the resistance in air and that of the target gas reached maximum at the operating temperature of 300 °C. The gas response of the Zr-added CaFe 2 O 4 -based sensor at 300 °C was estimated to be 2.5 times higher than that of the sensor made from pure CaFe 2 O 4 powder. However, the 90% response time of the Zr-added CaFe 2 O 4 -based sensor was much quicker at 350 °C than that at 300 °C. Thus, the optimal gas sensing performance of the Zr-added CaFe 2 O 4 -based sensor is expected to be obtained at the operating temperature of 350 °C, considering the still higher response to CO 2 gas at this temperature. It is noted that the present CaFe 2 O 4 -based sensor responded reversibly as well as continuously to CO 2 gas. Infrared analysis revealed that the sensing mechanism of the present CaFe 2 O 4 -based sensor is the change in the electric resistance of CaFe 2 O 4 caused by reactive CO 2 adsorption with negatively charged oxide ions (O - ) resulting in the increase in the hole concentration in the base material of CaFe 2 O 4 .
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Formation of CaFe2O4 porous structure by addition of Zr in malic acid complex Reviewed
Yuki Obukuro, Kenji Obata, Ryosuke Maeda, Shigenori Matsushima, Yuji Okuyama, Naoki Matsunaga, Go Sakai*
Journal of the Ceramic Society of Japan 123 ( 10 ) 995 - 998 2015.10
Language：English Publishing type：Research paper (scientific journal)
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Preparation and Characterization of Heterobimetallic Complex, Sr[Bi(DTPA)]・9H2O, Derived La-doped Sr2Bi2O5 Reviewed
Yuki Obukuro, Go Sakai*, Yuji Okuyama, Naoki Matsunaga, Shigenori Matsushima, Kenji Obata, Eiji Asato
Chemistry Letters 44 ( 7 ) 890 - 892 2015.7
Language：English Publishing type：Research paper (scientific journal)
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酒井 剛, 林 勝義
Electrochemistry 83 ( 4 ) 268 - 268 2015
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Electrochemical Society of Japan
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Obukuro Yuki, Sakai Go, Okuyama Yuji, Matsunaga Naoki, Matsushima Shigenori, Obata Kenji, Asato Eiji
Chemistry Letters 44 ( 7 ) 890 - 892 2015
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Chemical Society of Japan
Single-phase Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> was formed by calcination of the heterobimetallic complex, Sr[Bi(DTPA)]·9H<sub>2</sub>O, at 700 °C for 6 h in air. La-doping by 5 and 10 mol % into Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> was also examined. There were no traces of impurity phase in the 5 mol % La-doped Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> powder, on the other hand, impurity phases such as Sr<sub>3</sub>Bi<sub>4</sub>O<sub>9</sub> and SrCO<sub>3</sub> were identified for the 10 mol % La-doped sample. UV–vis spectroscopy revealed that the absorption edge of La-doped Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> exhibits red shift as compared to the pure Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> and the shift increases with the increase of La<sup>3+</sup> doping. It was confirmed that the photocatalytic activity of Sr<sub>2</sub>Bi<sub>2</sub>O<sub>5</sub> for the oxidation of isopropanol is improved with La doping under visible-light irradiation (λ ≥ 420 nm).
DOI： 10.1246/cl.150178
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Formation of CaFe<sub>2</sub>O<sub>4</sub> porous structure by addition of Zr in malic acid complex
OBUKURO Yuki, OBATA Kenji, MAEDA Ryosuke, MATSUSHIMA Shigenori, OKUYAMA Yuji, MATSUNAGA Naoki, SAKAI Go
Journal of the Ceramic Society of Japan 123 ( 1442 ) 995 - 998 2015
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
The effect of Zr addition into malic acid complex was examined for the purpose of the improvement of microstructure and specific surface area of CaFe<sub>2</sub>O<sub>4</sub>. The CaFe<sub>2</sub>O<sub>4</sub> phase could be obtained for both unadded and Zr-added (5 and 10 mol % with respect to Fe) system by calcination of precursor derived from malic acid complex at 700°C which is almost 200°C lower than that of conventional solid-state reaction method. Among the examined products, only the 5 mol % Zr-added product revealed characteristic smaller grains connected three dimensional porous structures resulting in higher specific surface area compared with unadded and 10 mol % Zr-added products. XPS measurements revealed that there are no notable changes in valence state for all constituent elements. The obtained final product of 5 mol % Zr-added CaFe<sub>2</sub>O<sub>4</sub> is worth further investigate for various application from a view point of improved higher specific surface area and characteristic microstructure as well as the functionality of the material itself.
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MATSUNAGA Naoki, SUGAHARA Mariko, SAKAI Go
Journal of the Ceramic Society of Japan 122 ( 1428 ) 613 - 617 2014.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
Synthesis of <i>c</i>-axis grown β-Ni(OH)<sub>2</sub> was attempted by rapid hydrolysis and/or direct hydrothermal treatment of the mixed solution of NiCl<sub>2</sub>, HCl and NH<sub>3</sub>. The UV–vis spectra revealed the addition of NH<sub>3</sub> into NiCl<sub>2</sub> solution shifted the peak position to shorter wavelength, indicating the formation of nickel ammine complex. Hydrolysis of the mixed solution containing nickel ammine complex gave β-Ni(OH)<sub>2</sub> particles. The amount of NH<sub>3</sub> in the mixed solution did not affect the crystallinity or morphology of the β-Ni(OH)<sub>2</sub> particle by the conventional rapid hydrolysis. Hydrothermal treatment of the hydrolyzed β-Ni(OH)<sub>2</sub> particles was changed the morphology from agglomerated particles to nanosheets-linked structure or hexagonal plates. However, any crystal growth or particular-axis growth was not recognized. Then, the direct hydrothermal treatment of the mixed solution was attempted. The direct treatment at certain amount of coexisting NH<sub>3</sub> gave small amount of the precipitates, and the precipitates showed distinctive XRD pattern of <i>c</i>-axis grown β-Ni(OH)<sub>2</sub>. The electrochemical property of the <i>c</i>-axis grown β-Ni(OH)<sub>2</sub> structures indicated that the diffusion control was the rate-determining step for the charge/discharge process.
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Electrochemical properties of anisotropic nickel hydroxide structures synthesized from nickel ammine complexes Reviewed
Naoki Matsunaga, Mariko Sugahara, Go Sakai
Journal of the Ceramic Society of Japan 122 ( 8 ) 613 - 617 2014.8
Language：English Publishing type：Research paper (scientific journal)
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Electrochemical and ESR Study on Pt-TiOx/C Electrocatalysts with Enhanced Activity for ORR Reviewed
Sakai G., Arai T., Matsumoto T., Ogawa T., Yamada M., Sekizawa K., Taniguchi T.
ChemElectroChem 1 ( 2 ) 366 - 370 2014.2
Language：English Publishing type：Research paper (scientific journal) Publisher：ChemElectroChem
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Pt-TiO x /C electrocatalysts possess specific activities for the oxygen reduction reaction of about 1.5times higher than that of conventional Pt/C. Electron-spin resonance spectra suggest that the specific activity of Pt-TiO x /C is related to the amount of ESR-active species.
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Sakai G., Sugahara M.
Journal of Applied Electrochemistry 42 ( 6 ) 367 - 374 2012.6
Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Electrochemistry
Nanostructure control of β-Ni(OH) 2 was attempted by adopting hydrothermal treatment for the high specific surface area (high-SSA) β-Ni(OH) 2 in the presence of guanidine carbonate. β-Ni(OH) 2 nanosheets-linked structures could be synthesized from high-SSA β-Ni(OH) 2 owing to the strong effects of guanidine carbonate for keeping or enlarging SSA during hydrothermal treatment. The discharging capacities of the high-SSA sample showed the highest capacity above 80 % at 0.2C. However, the capacities were decreased with decreasing SSA of the β-Ni(OH) 2 prepared. It was also found that, at lower SSA, charging/discharging rates below 1C did not affect the discharging capacity, i.e., the almost same capacities for 0.2C and 1C. Cyclic voltammetry revealed that the electrochemical reactions for the charging/discharging were considered to be reversible and smooth at various scanning rates. The rate-determining step of the electrochemical reaction is considered to be regulated by the diffusion of the active species involved for the lower SSA samples. However, for the higher SSA sample (280 m 2 g -1 ) obtained at 200 °C in the presence of 1.0 × 10 -1 mol L -1 guanidine carbonate strongly indicates the effects of the rate of surface reaction or electronic conductivity on rate-determining step of charging/discharging of the material. © 2012 Springer Science+Business Media B.V.
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Synthesis of Ni(OH)2 nanostructures by the hydrothermal treatment in the presence of guanidine carbonate and their electrochemical properties Reviewed
Go Sakai, Mariko Sugahara
Journal of Applied Electrochemistry 42 367 - 374 2012.4
Language：English Publishing type：Research paper (scientific journal)
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Double layer capacitance of high surface area carbon nanospheres derived from resorcinol-formaldehyde polymers Reviewed
Daisuke Tashima, Eri Yamamoto, Nanami Kai, Daisuke Fujikawa, Go Sakai, Masahisa Otsubo, Tsuyoshi Kijima
Carbon 49 4848 - 4857 2011.11
Language：English Publishing type：Research paper (scientific journal)
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Tashima D., Yamamoto E., Kai N., Fujikawa D., Sakai G., Otsubo M., Kijima T.
Carbon 49 ( 14 ) 4848 - 4857 2011.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Carbon
Micro-mesoporous bimodal carbon nanospheres with high surface areas were synthesized by a combined use of surfactant templating technique and BaO 2 chemical activation one. Starting spherical nanopolymer/surfactant composites were prepared by the NaOH-catalyzed reaction of resorcinol (R) and formaldehyde (F) in the presence of cetyltrimethylammonium bromide (CTAB) as a core template and 1,3,5-trimethylbenzene (TMB) and tert-butanol (t-BuOH) as cosurfactants. After pretreatment with hydrochloric acid, the composite materials were calcined at 1000 °C in N 2 coexistent with varying weight ratios of BaO 2 to RF polymer ranging from 0 to 11. It produced micro-mesoporous bimodal carbon nanospheres of 124-143 nm diameter, with specific surface areas as high as 1884 m 2 g -1 or up to 3301 m 2 g -1 , in contrast to microporous ones with smaller surface areas obtained at low BaO 2 -loadings. The electrochemical double layer capacitance of the resulting nanocarbons in 0.5 M H 2 SO 4 showed a marked increase with specific surface areas, up to as high as 219 F g -1 for the highest surface area carbon material. © 2011 Elsevier Ltd. All rights reserved.
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Carbon-Supported Growth of Cross-Linked Platinum Nanowires by Surfactant Templating and Their Elecrochemical Characterization Reviewed
M. Uota, Y. Hayashi, A. Ohyama, H. Takemoto, R. Iriki, T. Kishishita, M. Shimoda, T. Yoshimura, H. Kawasaki, G. Sakai, T. Kijima
Journal of Nanoscience and Nanotechnology 10 ( 9 ) 5790 - 5795 2010.11
Language：English Publishing type：Research paper (scientific journal)
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Uota M., Hayashi Y., Ohyama K., Takemoto H., Iriki R., Kishishita T., Shimoda M., Takumi Y., Hideya K., Sakai G., Kijima T.
Journal of Nanoscience and Nanotechnology 10 ( 9 ) 5790 - 5795 2010.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Nanoscience and Nanotechnology
Platinum/carbon (Pt/C) composite materials were prepared by the hydrazine reduction of H 2 PtCI 6 confined to a mixed surfactant lytropic liquid crystal (LC)/C mixture with varying amounts of water. The reaction at relatively low water contentssuccessfully yielded cross-linked Pt nanowires with wire-widths of 2-5 nm. The novel Pt nanostructure is believed to be from poorly hydrated hexagonal domains formed together with layered domains by the phase separation of the precursory LC mixture in the presence of carbon. Electrochemical measurements using cyclic volutammetry and membrane electrode assemblies revealed that the cross-linked nanowired Pt/C composite exhibits fairly high electrocatalytic activity for oxygen reduction reaction, as well as a high performance as the cathode material for polymer electrolyte fuel cells. © 2010 American Scientific Publishers.
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Synthesis of b-Ni(OH)2 hexagonal plates and electrochemical behavior as a positive electrode material Reviewed
Go Sakai, Makoto Miyazaki, Tsuyoshi Kijima
Journal of The Electrochemical Society 157 A932 - A939 2010.8
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Miyazaki M., Kijima T.
Journal of the Electrochemical Society 157 ( 8 ) 2010.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society
Β-Ni (OH) 2 hexagonal plates were synthesized from the high specific surface area nickel hydroxide by adopting the solvothermal treatment, i.e., heat-treatment of nickel hydroxide in a closed vessel in the presence of the disperse phase. An aqueous ammonia solution was chosen as the disperse phase, and it was effective for producing unit cell derived hexagonal particles even at a relatively low temperature of around 80°C. A wide variety of sizes and specific surface areas of the hexagonal Β-Ni (OH) 2 could be available by choosing the solvothermal conditions such as amount and concentration of ammonia solution as the disperse phase as well as treatment temperature. The solvothermally synthesized hexagonal plates showed stable discharging behavior without serious deterioration in the discharging capacity when relatively high charge/discharge rates were adopted. It was speculated that there is a suitable specific surface area for the hexagonal particles to achieve a higher discharging capacity at high charge/discharge rates. © 2010 The Electrochemical Society.
DOI： 10.1149/1.3446847
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Synthesis of high-surface-area beta-Ni(OH)2 and its transformation into nanosheets and nanodisks by hydrothermal treatment Reviewed
Go Sakai, Makoto Miyazaki, Tsuyoshi Kijima
Journal of The Electrochemical Society 157 A480 - A486 2010.4
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Miyazaki M., Kijima T.
Journal of the Electrochemical Society 157 ( 4 ) 2010.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society
We report here a simple method to synthesize an extremely high specific surface area (SSA) Β-Ni (OH) 2 by a rapid hydrolysis technique. The combination of nickel salt and a strong alkaline solution precipitated Β-Ni (OH) 2 with an extremely high SSA (beyond 200 m 2 /g up to 239 m 2 /g). Furthermore, the hydrothermal treatment of the as-precipitated nickel hydroxide at low temperatures, 100-120°C, was found to generate an aggregate of Β-Ni (OH) 2 nanosheets with high SSA around 190 m 2 g-1. A similar treatment at temperatures as high as 200°C led to the formation of Β-Ni (OH) 2 nanodisks with a low surface area of 39 m 2 g -1 . The discharging capacity of the as-precipitated high SSA Β-Ni (OH) 2 showed a strong dependence on the charging/discharging rate, with a fairly high capacity at a charging/discharging rate of 0.2C. The hydrothermally synthesized nanosheets and nanodisks showed relatively stable discharging characteristics over a wide range of charging/discharging rates ranging from 0.2 to 10C. Especially, the nanodisk material was found to stand the high rate charging/discharging and cause no deterioration in the discharging capacity, although the discharging capacity itself was low. © 2010 The Electrochemical Society.
DOI： 10.1149/1.3298456
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Electrocemical properties of the nickel hydroxide hexagonal plates as positive electrode material
Sakai Go, Miyazaki Makoto, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2010 ( 0 ) 1F33 - 1F33 2010
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Kijima T., Isayama T., Sekita M., Uota M., Sakai G.
Journal of Alloys and Compounds 485 ( 1-2 ) 730 - 733 2009.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Alloys and Compounds
Terbium (III)-doped yttrium oxysulfate Y 2 O 2 SO 4 :Tb 3+ was synthesized by the 1000 °C calcination of Tb 3+ -doped dodecylsulfate-templated yttrium oxide mesophases with straight-layered (S-type) and concentric-layered (C-type) structures. The Tb 3+ -doped oxysulfates exhibited luminescence bands including the 5 D 4 - 7 F 5 transition with a tendency in intensity to saturate or reach a maximum at 13-25 mol% Tb doping. The maximum intensity of Tb 3+ emission for the C-type-mesophase-mediated Y 2 O 2 SO 4 :Tb 3+ was 1.44 times stronger than that for the S-type-mesophase-mediated analogues, although the Eu 3+ emissions for C-type-mesophase-mediated Y 2 O 2 SO 4 :Eu 3+ was enhanced in intensity up to three times stronger than those for S-type-mesophase-mediated ones. It is suggested from FT-IR data that any specific deformation of sulfate groups is induced for both emission systems by the conversion of concentric dodecylsulfate-layers into straight sulfate-layers in the oxysulfate framework upon calcination. This leads to the enhanced emission for the Eu 3+ -doped system, whereas the emission of Tb 3+ in the same Y 2 O 2 SO 4 matrix is slightly enhanced because the electronic state of 4f 8 for Tb 3+ ion is insensitive to the change of the distribution of the surrounding negative-charged oxide ions. © 2009 Elsevier B.V. All rights reserved.
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Kijima T., Nagatomo Y., Takemoto H., Uota M., Fujikawa D., Sekiya Y., Kishishita T., Shimoda M., Yoshimura T., Kawasaki H., Sakai G.
Advanced Functional Materials 19 ( 4 ) 545 - 553 2009.2
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Advanced Functional Materials
Nanohole-structured single-crystalline Pt nanosheets have been synthesized by the borohydride reduction of Na 2 PtCl 6 confined to the lyotropic liquid crystals (LLCs) of polyoxyethylene (20) sorbitan monooleate (Tween 80) with or without nonaethylene-glycol (C 12 EO 9 ). The Pt nanosheets of around 4-10 nm in central thickness and up to 500 nm or above in diameter have a number of hexagonal-shaped nanoholes ∼1.8nm wide. High-resolution electron microscope images of the nanosheets showed atomic fringes with a spacing of 0.22 nm indicating that the nanosheets are crystallographically continuous through the nanoholed and non-holed areas. The inner-angle distributions for the hexagonal nanoholes indicate that the six sides of the nanoholes are walled with each two Pt (111 ), Pt (11̄1 ) and Pt (010) planes. The formation mechanism of nanoholed Pt nanosheets is discussed on the basis of structural and compositional data for the resulting solids and their precursory LLCs, with the aid of similar nanohole growth observed for a Tween 80 free but oleic acid-incorporated system. It is also demonstrated that the nanoholed Pt nanostructures loaded on carbon exhibit fairly high electrocatalytic activity for oxygen reduction reaction and a high performance as a cathode material for polymer-electrolyte fuel cells, along with their extremely high thermostability revealed through the effect of electronirradiation. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.
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Synthesis of Nanohole-Structured Single-Crystalline Platinum Nanosheets Using Surfactant-Liquid-Crystals and Their Electrochemical Characterization Reviewed
Tsuyoshi Kijima, Yu Nagatomo, Hirokatsu Takemoto, Masafumi Uota, Daisuke Fujikawa, Yuzo Sekiya, Teppei Kishishita, Keisuke Shimoda, Takumi Yoshimura, Hideya Kawasaki, Go Sakai
Advanced Functional Materials 19 545 - 553 2009.2
Language：English Publishing type：Research paper (scientific journal)
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Cathode properties of high-surface-area nickel hydroxide nanostructures
Sakai Go, Miyazaki Makoto, Matsunaga Mana, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2009 ( 0 ) 1H05 - 1H05 2009
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Synthesis and Characterization of Nanoshell Structured Carbon Nanospheres and Nanowires
Otsuka Akio, Matsumura Yuko, Kai Nanami, Iriki Ryosuke, Takemoto Hirokatsu, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2009 ( 0 ) 2PF08 - 2PF08 2009
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Yoshimura T., Uota M., Kuwahara T., Fujikawa D., Kawasaki H., Sakai G., Kijima T.
Materials Research Bulletin 43 ( 5 ) 1282 - 1290 2008.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Materials Research Bulletin
Using transmission electron microscopy (TEM) electron irradiation effects were studied for nanogroove-network structured single-crystalline and dendritic polycrystalline Pt nanosheets 50-60 nm in size. These two nanosheets with nearly the same average groove-width or dendritic spacing of 1.3-1.4 nm were prepared from the mixed and single surfactant liquid crystalline templates, respectively. On exposure to electron beam for 20 min at the acceleration voltage of 200 kV, the nanogrooved nanosheets were morphologically little affected, but the dendritic ones were transformed into less branched polycrystalline structures with spacings distributed around ∼1.7 nm. The shape transformation of the latter occurred by the combined mechanism of segmental migration and atomic diffusion. These observations indicate that the nanogrooved Pt nanosheets are highly stabilized by the grooved but crystallographically continuous Pt framework, leading to their extremely high thermo-resistance, in marked contrast to the polycrystalline dendritic structures constructed of crystallographically discontinuous linkages of nanoblocks. © 2007 Elsevier Ltd. All rights reserved.
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Abnormally Enhanced Eu3+ Emission in Y2O2SO4:Eu3+ Inherited from Their Precursory Dodecylsulfate-Templated Concentric-Layered Nanostructure Reviewed
T. Kijima, T. Shinbori, M. Sekita, M. Uota, G. Sakai
Journal of Luminescence 128 311 - 316 2008.4
Language：English Publishing type：Research paper (scientific journal)
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Effect of Electron Irradiation on Nanogroove-Networked Single-crystalline and Dendritic Polycrystalline Platinum Nanosheets Prepared from Lyotropic Surfactant Liquid-Crystal Templates Reviewed
T. Yoshimura, M. Uota, T. Kuwahara, D. Fujikawa, H. Kawasaki, G. Sakai, T. Kijima
Materials Research Bulletin 43 1282 - 1290 2008.3
Language：English Publishing type：Research paper (scientific journal)
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Additive-stabilized hexagonally ordered mixed lyotropic liquid crystal Reviewed
D. Li, D. Fujikawa, T. Yoshimura, M. Uota, G. Sakai, T. Kijima
Journal of Molecualr Liquids 138 113 - 119 2008.3
Language：English Publishing type：Research paper (scientific journal)
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Kijima T., Shinbori T., Sekita M., Uota M., Sakai G.
Journal of Luminescence 128 ( 3 ) 311 - 316 2008.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Luminescence
A new nanostructure-mediated approach was demonstrated to synthesize Eu 3+ -doped yttrium oxysulfates Y 2 O 2 SO 4 :Eu 3+ giving rise to abnormally enhanced Eu 3+ emission. Yttrium and europium salts, sodium dodecylsulfate (SDS), and urea at various Eu 3+ concentrations were reacted in aqueous solution at 80, 85, and 87 °C to yield Eu 3+ -doped dodecylsulfate-templated yttrium oxide mesophases with straight-layered (S-type), concentric-layered (C-type) and layer-to-hexagonal transient-layered (T-type) structures, respectively. On calcination at 1000 °C, all of these mesophases were converted into Y 2 O 2 SO 4 :Eu 3+ to exhibit luminescence bands including the 5 D 0 - 7 F 2 transition with a tendency in intensity to saturate or reach a maximum at 10-12 mol% Eu doping. The Eu 3+ emissions for Y 2 O 2 SO 4 :Eu 3+ mediated by the T- and C-type mesophases were enhanced in intensity by a factor of about two and three times, respectively, stronger than those for not only compositionally the same sulfate Y 2 O 2 SO 4 :Eu 3+ obtained from yttrium-based sulfates but also Y 2 O 3 :Eu 3+ obtained in the SDS-free system. In contrast, the emission intensities for the S-type-mesophase-mediated Y 2 O 2 SO 4 :Eu 3+ were close to those for the latter sulfates. The abnormally enhanced emission is likely based on specific deformation of sulfate groups induced through the conversion of concentric dodecylsulfate-layers to straight sulfate-layers in the oxysulfate framework upon calcination. © 2007 Elsevier B.V. All rights reserved.
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Additive-stabilized hexagonally ordered mixed lyotropic liquid crystal
Li D., Fujikawa D., Yoshimura T., Uota M., Go sakai, Kijima T.
Journal of Molecular Liquids 138 ( 1-3 ) 113 - 119 2008.2
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Molecular Liquids
A strategy for preparing mixed lyotropic liquid crystals (LLCs) possessing a stable 2-D hexagonal mesostructure is demonstrated, which can be controlled easily and reproducibly through the use of both hydrophobic dopings and inorganic cations serving as additives. By using small molecules such as LiCl and anthracene, respectively, the cylindrical micelles of mixed amphiphiles can spontaneously assemble into 2-D hexagonal mesophase. This kind of mixed amphiphiles may be used as stable templates for synthesis of templated nanomaterials. © 2007 Elsevier B.V. All rights reserved.
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Size controlled spherical carbones templated by surfactant assemblies
Ohtsuka Akio, Kai Nanami, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2008 ( 0 ) 596 - 596 2008
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Hydrothermal transformation of high-surface-area b-Ni(OH)<sub>2</sub> into nanostructures
Sakai Go, Miyazaki Makoto, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2008 ( 0 ) 694 - 694 2008
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Kawasaki H., Uota M., Yoshimura T., Fujikawa D., Sakai G., Arakawa R., Kijima T.
Langmuir 23 ( 23 ) 11540 - 11545 2007.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Langmuir
We report the fabrication of self-organized surfactant nanofibers containing platinum ions on a highly oriented pyrolytic graphite (HOPG) surface from mixed solutions of hexadecyltrimethylammonium hydroxide (C16TA0H) and hydrogen hexachloroplatinate (IV) (H2PtCl6). The fibrous surfactant self-assembly was stable in air, even after being soaked in water, in contrast to surfactant hemicylindrical micelles, which are stable only at graphite/solution interfaces. The results show that the graphite surface served as an essential template for the specific formation of fibrous surfactant self-assemblies. In addition, when surfactant nanofibers containing metal ions were treated with hydrazine, platinum nanoparticles concentrated in the nanofibers formed on the HOPG surface. We also prepared surfactant nanofibers containing gold ions on HOPG surfaces and formed gold nanoparticles in the nanofibers. © 2007 American Chemical Society.
DOI： 10.1021/la701020s
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Performance evaluation of MEA by accumulating structure of catalyst layer
Shibata Koichiro, Yaoka Toshinari, Tashima Daisuke, Sakai Go, Otsubo Masahisa
Memoirs of the Faculty of Engineering, Miyazaki University 36 127 - 131 2007.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Miyazaki University
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Kondo Y., Harima Y., Hyakutake K., Yamada N., Uota M., Sakai G., Kijima T.
Colloid and Polymer Science 285 ( 9 ) 1019 - 1027 2007.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Colloid and Polymer Science
The composite films of poly(lactic acid) (PLA) doped with glucosamine(Gluc)-formaldehyde(FA) polymer/sodium dodecylbenzenesulfonate (SDBS) complexes at 1-5 wt% were synthesized to demonstrate striking improvement of their structural and mechanical properties. The polymer complexes were obtained by the hydrothermal polymerization of Gluc and FA at a molar ratio of 1:2 in the presence of SDBS. The atomic ratios of S in -SO 3 - to N in -NH 3 - (=S/N) in the polymer complexes limitedly range from 0.52 to 0.69, indicating that the complexation develops through the nonstoichiometric reaction between -NH 3 + groups of (Gluc-FA) polymer and -SO 3 - ones of SDBS and 31-48% of the -NH 3 + groups remain unbound. The PLA composite film doped with 1 wt% (Gluc-FA)/SDBS showed the elongation-at-break of as large as 194% compared with 37% for PLA film, together with an appreciable increase of the crystallites size (D 200 ) of PLA from 21.8 to 33.3 nm. © Springer-Verlag 2007.
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Fujikawa D., Uota M., Sakai G., Kijima T.
Carbon 45 ( 6 ) 1289 - 1295 2007.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Carbon
The NaOH-catalyzed polymerization of resorcinol (R) and formaldehyde (F) confined to the vesicular assemblies of cetyltrimethylammonium bromide as a core template mixed with 1,3,5-trimethylbenzene and tert-butanol (tBuOH) as cosurfactants yielded RF polymer/cetyltrimethylammonium composite nanowires and nanospheres depending on the amount of tBuOH. Carbonization of the resulting nanpolymers led to microporous carbon nanowires of 45-240 nm diameter and nanospheres of 260-650 nm diameter. Similar but a little modified reactions successfully resulted in monodispersed carbon nanospheres of ca. 280 nm diameter as well as monodispersed carbon nanowires of ca. 70 nm diameter with a high surface area of 1777 m 2 /g. The present approach could be further extended to the synthesis of a wide range of carbon nanomaterials by using various surfactants and cosurfactants. © 2007 Elsevier Ltd. All rights reserved.
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Self-organization of Surfactant-Metal Ion Complex Nanofibers on Graphite Surfaces and Their Application to the Fibrously Concentrated Platinum Nanoparticles Formation Reviewed
H. Kawasaki, M. Uota, T. Yoshimura, D. Fujikawa, G. Sakai, R. Arakawa, T. Kijima
Langmuir 23 11540 - 11545 2007.4
Language：English Publishing type：Research paper (scientific journal)
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Kijima T., Nishida Y., Fujikawa D., Uota M., Yoshimura T., Sakai G.
Journal of Molecular Liquids 133 ( 1-3 ) 54 - 60 2007.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Molecular Liquids
The structural change and phase transition in the mixed surfactant liquid crystalline (LC) system of nonaethyleneglycol dodecylether (C 12 EO 9 ), polyoxyethylene (20) sorbitan monostearate (Tween 60) and water has been studied on addition of primary alcohols C n H 2n+1 OH (C n OH, n = 10, 12, and 14) or replacement of C 12 EO 9 with C n OH. In the alcohol-added systems, the C 12 EO 9 /Tween 60/C n OH/H 2 O mixture at a 1:1:x:60 molar ratio for n = 12 undergoes hexagonal to layered phase transition just beyond the critical composition of x = 0.5, whereas the phase transitions for n = 10 and 14 occur at lower compositions. In the alcohol-replaced C 12 EO 9 /Tween 60/C n OH/H 2 O systems at a 1 - y:1:y:60 molar ratio, the hexagonal LC structures for n = 10 and 12 are kept up to y = 0.5 and 0.7, respectively, although the hexagonal phase for n = 14 is transformed into a layered structure beyond y = 0.3. The y = 0.3 composition for n = 12 affords a very highly ordered hexagonal LC, even compared with the alcohol-free phase. The rod-to-rod distance for the hexagonal LCs consisting of cylindrical rodlike micelles in the alcohol-replaced systems increases remarkably with an increase of y, in contrast to a slight increase for the same parameter in the alcohol-added systems. The phase transition mechanism is also discussed. © 2006 Elsevier B.V. All rights reserved.
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Synthesis and characterization of poly(lactic acid) and glucosamine-formaldehyde/dodecylbenzenesulfonate composite films
Y. Kondo, Y. Harima, K. Hyakutake, N. Yamada, M. Uota, G. Sakai, T. Kijima
Colloid and Polymer Science 285 1019 - 1027 2007.3
Language：English Publishing type：Research paper (scientific journal)
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Shape-controlled Nanocarbons from Vesicular Assemblies-templated Resorcinol-Formaldehyde Nanopolymers Reviewed
Daisuke Fujikawa, Masafumi Uota, Go Sakai, Tsuyoshi Kijima
Carbon 45 1289 - 1295 2007.3
Language：English Publishing type：Research paper (scientific journal)
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Long-Chain Alcohol Induced Phase Transition in Lyotropic Mixed Polyoxyethylene-type Surfactant Liquid-Crystals Reviewed
Tsuyoshi Kijima, Yuki Nishida, Daisuke Fujikawa, Masafumi Uota, Takumi Yoshimura, Go Sakai
Journal of Molecular Liquids 133 54 - 60 2007.2
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Yoshimura T., Isohata S., Uota M., Kawasaki H., Kuwahara T., Fujikawa D., Kijima T.
Advanced Materials 19 ( 2 ) 237 - 241 2007.1
Language：English Publishing type：Research paper (scientific journal) Publisher：Advanced Materials
The synthesis of nanogroove-network-structured single-crystalline Platinum (Pt) nanosheets and the method for loading the nanogrooved Pt nanosheets on a Carbon support using a mixed-surfactant templating approach is discussed. The resulting nanogrooves-networked Pt on the carbon support (Pt/C) was also demonstrated to exhibit fairly high electrocatalytic activity for oxygen reduction reactions. The nanogroove-network structured single-crystalline Pt nanosheets were obtained by the reduction of Na 2 PtCl 6 confined to the lyotropic mixed LCs of polyoxyethylene and nanoethyleneglycol dodecylether. Atomic force microscopy (AFM) images of the resulting black powders showed a multilayered aggregate of rounded to elliptic nanosheets. The results showed that the Pt material consisted of single-crystalline nanosheets that are composed of pseudo-2D irregular shape networks of loosely interconnected Pt nanoleaves.
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Synthesis of Nanogroove-Network Structured Platinum Nanosheets and Their Carbon-supported Forms by Mixed Surfactant-Templating Approach Reviewed
Go Sakai, Takumi Yoshimura, Shusaku Isohata, Masafumi Uota, Hideya Kawasaki, Takeshi Kuwahara, Daisuke Fujikawa, Tsuyoshi Kijima
Advanced Materials 19 237 - 241 2007.1
Language：English Publishing type：Research paper (scientific journal)
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Evaluation of Characteristics of MEA as Multi Catalyst Layer (3).
Yaoka Toshinari, Hidaka Hiroaki, Tashima Daisuke, Sakai Go, Otsubo Masahisa
Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 2007 ( 0 ) 452 - 452 2007
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Committee of Joint Conference of Electrical, Electronics and Information Engineers in Kyushu
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Nagatomo Yu, Uota Masafumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2007 ( 0 ) 682 - 682 2007
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Synthesis and characterization of high surface area nickel hydroxide by rapid hydrolysis method
Sakai Go, Miyazaki Makoto, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2007 ( 0 ) 139 - 139 2007
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Uota Masafumi, Hayashi Yuuichi, Yoshimura Takumi, Kawasaki Hideya, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2007 ( 0 ) 681 - 681 2007
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Kawasaki H., Sakai G., Kijima T.
Applied Surface Science 253 ( 3 ) 1512 - 1516 2006.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Applied Surface Science
The shape transformation of platinum (Pt) nanosheets with a uniform thickness of as thin as 3.5 ± 1 nm supported on graphite was investigated by in situ atomic force microscopy (AFM). The AFM observations revealed the shape transformation and the coalescence in preferred directions for the Pt nanosheets at room temperature (25 °C), which is much lower than the melting point of bulk metallic platinum (1769 °C). The behavior may be attributed to the high surface energy for the edge parts of Pt nanosheets with the small curvature of the nanometer scale. © 2006 Elsevier B.V. All rights reserved.
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Synthesis of resorcinol-based polymer nanowires templated by surfactant assemblies
Fujikawa D., Uota M., Yoshimura T., Sakai G., Kijima T.
Polymer Preprints, Japan 55 ( 1 ) 2006.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan
Recently, we have reported the synthesis of resorcinol-formaldehyde (RF) polymer nanospheres and microwires in the presence of cationic surfactant as a template. Here we report the synthesis and formation mechanism of RF polymer nanowires of 80-300nm diameter by a similar reaction using TMB. The coexisting effect of alcohol on the morphological properties of RF polymers is also reported.
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Kawasaki H., Uota M., Yoshimura T., Fujikawa D., Sakai G., Kijima T.
Journal of Colloid and Interface Science 300 ( 1 ) 149 - 154 2006.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Colloid and Interface Science
One-dimensional (1-D) self-assemblies of Pt nanoparticles on a graphite surface have been synthesized via a template-directed sintering process of individual nanoparticles, using nonionic/cationic mixed hemicylindrical micelle templates of dodecyldimethylamine oxide surfactant at graphite/solution interfaces. The dimension and morphology of Pt nanoparticles can be widely controlled by the concentration of Pt ions equivalent to the mixing ratio of nonionic and cationic species in the surfactant micelle. This approach could be extended to fabricate a wide range of self-assembling metallic nanostructures on surfaces using various nonionic/cationic mixed micelle-like self-assemblies carrying metal ions at interfaces, while providing a fundamental insight into a 1-D self-assembly from individual nanoparticles. © 2006 Elsevier Inc. All rights reserved.
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One-Dimensional Assemblies of Platinum Nanoparticles on a Graphite Surface Using Nonionic/Ionized Mixed Hemicylindrical Micelle Templates Reviewed
Hideya Kawasaki, Masafumi Uota, Takumi Yoshimura, Daisuke Fujikawa, Go Sakai, Tsuyoshi Kijima
Journal of Colloid and Interface Science 300 149 - 154 2006.6
Language：English Publishing type：Research paper (scientific journal)
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Synthesis of micro-mesoporous bimodal silica nanoparticles using lyotropic mixed surfactant liquid-crystal templates Reviewed
Hiroshi Mori, Masafumi Uota, Daisuke Fujikawa, Takumi Yoshimura, Takeshi Kuwahara, Go Sakai, Tsuyoshi Kijima
Microporous and Mesoporous Materials 91 172 - 180 2006.5
Language：English Publishing type：Research paper (scientific journal)
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Mori H., Uota M., Fujikawa D., Yoshimura T., Kuwahara T., Sakai G., Kijima T.
Microporous and Mesoporous Materials 91 ( 1-3 ) 172 - 180 2006.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Microporous and Mesoporous Materials
Micro-mesoporous bimodal silica nanoparticles with a particle diameter of as small as 40-90 nm have been synthesized by a two-step reaction based on the polymerization of silicate (TEOS) species confined to the mixed surfactant hexagonal-structured liquid-crystal (LC) templates of nonaethyleneglycol dodecylether (C 12 EO 9 ) and polyoxyethylene (20) sorbitan monostearate (Tween60) or eicosaethyleneglycol octadecyl ether (C 18 EO 20 ). After pre-aging for water-insolubilization, the LC phase was kept in contact with dilute aqueous solution of ammonium acetate to achieve full condensation of silicate species. The catalyst-free pre-aging treatment induces the separation of the LC phase into domains and the subsequent water-phase-in-contact process se rves to maintain the hexagonal framework by removing the ethanol evolved through hydrolysis. On calcination the hexagonal array of mixed surfactant cylindrical micelles in the LC templates is converted into a hexagonal structure of mesopores with some irregularity in pore arrangement, separated by silica walls with irregularly arranged micropores. Throughout aging and calcination, the hexagonal framework of the silicate-loaded LC or condensed particles in the Tween60 based mixed surfactant system contract to yield silica nanoparticles with mesopores of ∼5 nm diameter and ∼2 nm-thick silica walls. In contrast, the framework in the other system remarkably expands to form mesopores of 4.6 nm diameter and silica walls of as thick as 4.7 nm, along with 1.5-2 times larger micropore volume and specific surface area. The striking difference between the structural parameters in both systems is arisen from the opposing effects due to the hydrophilic triple-branched or linear polyoxyethylene (PEO) chains of Tween60 and C 18 EO 20 molecules. © 2005 Elsevier Inc. All rights reserved.
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FUJIKAWA Daisuke, UOTA Masafumi, YOSHIMURA Takumi, SAKAI Go, KIJIMA Tsuyoshi
Chemistry letters 35 ( 4 ) 432 - 433 2006.4
Language：Japanese Publishing type：Research paper (scientific journal)
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Fujikawa D., Uota M., Yoshimura T., Sakai G., Kijima T.
Chemistry Letters 35 ( 4 ) 432 - 433 2006.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Thermosetting polymer nanospheres and nanowires have been synthesized by the NaOH-catalyzed polymerization of resorcinol and formaldehyde in the presence of cetyltrimethyl-ammonium bromide as a core template together with/without trimethylbenzene as an additive and topotactically converted into their carbonized forms. Copyright © 2006 The Chemical Society of Japan.
DOI： 10.1246/cl.2006.432
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Surfactant-templated Synthesis of Resorcinol-Formaldehyde Polymer and Carbon Nanostructures: Nanospheres and Nanowires Reviewed
Daisuke Fujikawa, Masafumi Uota, Takumi Yoshimura, Go Sakai, Tsuyoshi Kijima
Chemistry Letters 35 ( 4 ) 432 - 433 2006.4
Language：English Publishing type：Research paper (scientific journal)
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Morphological control of silica using polymer nanostructures
Okazaki Taro, Fujikawa Daisuke, Uota Masafumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2006 ( 0 ) 425 - 425 2006
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Study on morphological control of ceramic materials using polymer nanostrucrures
Fujikawa Daisuke, Okazaki Taro, Higuchi Yutaka, Uota Masafumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2006 ( 0 ) 348 - 348 2006
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Shinbori Tomohiro, Uota masashi, Sekita masami, Sakai Gou, Kijima Tuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2006 ( 0 ) 192 - 192 2006
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Synthesis and Characterization of Carbon / Sn nanocomposites
Uota Masafumi, Karasima Takeshi, Yoshimura Takumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2006 ( 0 ) 127 - 127 2006
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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酒井 剛
Electrochemistry 74 ( 10 ) 856 - 856 2006
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Electrochemical Society of Japan
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Fujikawa D., Uota M., Yoshimura T., Sakai G., Kijima T.
Polymer Preprints, Japan 54 ( 2 ) 4775 - 4776 2005.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan
Nanostructural polymer materials have been synthesized by resorcinol-formaldehyde copolymerization in the presence of CTAB with or without TMB. The resulting polymers in the TMB-free systems varied in morphology from spherical particles 250-400nm in diameter to microwires 10-30μm in diameter with an increase of NaOH content, x. in the TMB added systems, nanowires 80-300nm in diameter were obtained in place of the spherical polymers at the same NaOH content. It was also found that the nanostructure polymers are calcined in carbons while keeping their morphologies.
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Synthesis and template effects of resorcinol-based polymer nanostructures
Fujikawa D., Uota M., Yoshimura T., Sakai G., Kijima T.
Polymer Preprints, Japan 54 ( 1 ) 2005.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Polymer Preprints, Japan
Recently, we have reported the synthesis of phenol-furfural (or formaldehyde) polymer nanotubes in the presence of cationic surfactant as the template. But it was unsuccessful to apply these nanotubes to proton conductors and carbon precursors, due to chemical and thermal instability of their frameworks. Here we report the synthesis of nanostructural polymer materials through resorcinol-formaldehyde copolymerization in the presence of CnTAB (n=16, 18).
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Kawasaki H., Uota M., Yoshimura T., Fujikawa D., Sakai G., Annaka M., Kijima T.
Langmuir 21 ( 24 ) 11468 - 11473 2005.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Langmuir
Single-crystalline platinum nanosheets have been prepared via a new methodology based on the chemical reduction of a platinum salt (H 2 PtCl 6 ) with hydrazine at a graphite/solution interface, using polyoxyethylene (20)sorbitan monostearate (Tween 60) based self-assembly (hemicylindrical micelle) templates. The platinum nanosheets with a uniform thickness of as thin as 3.5 ± 1 nm are surface-smooth and continuous over relatively large length scales of micrometer sizes. In striking contrast to the Tween 60 based system, no Pt nanosheets are obtained with nonaethylene glycol monododecyl ether (C 12 EO 9 ) and polyoxyethylene (23) dodecyl ether (C 12 EO 23 ). No Pt nanosheets are also obtainable with a laterally homogeneous layer of Tween 60 formed at the silica/solution interface. These results indicate that surfactant Tween 60 molecules with a triple polyoxyethylene structure, as well as their hemicylindrical micelle templates, play an essential role for the formation of the Pt nanosheets. It is also suggested that the interfacially directed growth of Pt metals within the aqueous shells of the Tween 60 hemicylindrical micelles induces the thin Pt crystals as thick as the aqueous shells. The present approach could be extended to prepare a wide range of novel nanostructures of noble metals, using various micelle-like self-assemblies at interfaces. © 2005 American Chemical Society.
DOI： 10.1021/la051247i
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Single-Crystalline Platinum Nanosheets from Nonionic Surfactant 2-D Self-Assemblies at Solid/Aqueous Solution Interfaces
共著者：H. Kawasaki, M. Uota, T. Yoshimura, D. Fujikawa, G. Sakai, M. Annaka, T. Kijima
Langmuir, Vol. 21, No. 24, 11468-11473 (2005). 21 ( 24 ) 11468 - 11473 2005.11
Language：English Publishing type：Research paper (scientific journal)
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SAKAI Go, NAKATANI Tomoe, YOSHIMURA Takumi, UOTA Masafumi, KIJIMA Tsuyoshi
Chemistry letters 34 ( 10 ) 1364 - 1365 2005.10
Language：Japanese Publishing type：Research paper (scientific journal)
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Sakai G., Nakatani T., Yoshimura T., Uota M., Kijima T.
Chemistry Letters 34 ( 10 ) 1364 - 1365 2005.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
The spherical microparticles of SnO 2 were synthesized successfully by hydrothermal treatment of their precursor consisting of SnCl 4 and mixed surfactants, followed by calcination at 500°C. Copyright © 2005 The Chemical Society of Japan.
DOI： 10.1246/cl.2005.1364
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Synthesis of Polycrystalline Spherical SnO2 Microparticles via Hydrothermal Treatment in the Presence of Mixed Surfactants Reviewed
共著者：G. Sakai, T. Nakatani, T. Yoshimura, M. Uota, T. Kijima
Chemistry Letters, Vol. 34, No. 10, 1364-1365 (2005). 34 ( 10 ) 1364 - 1365 2005.10
Language：English Publishing type：Research paper (scientific journal)
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Cho H., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 109 ( 2 ) 307 - 314 2005.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A group of complex metal oxides, BiMeVOx, which a fraction (x) of V in Bi4V2O11is replaced by foreign metal, has been reported to be oxide-ionic conductors. The various kinds of oxides in this group, Me = Cu (x = 0.1), Zr (x = 0.1), Ti (x = 0.4), Nb (x = 0.15) and Ta (x = 0.15), were investigated for electrochemical characterization based on oxygen concentration battery. The powders of BiMeVOx, their structural phases to the high temperature phase (γ) of Bi4V2O11, were obtained by calcining at 700-850 °C. Each sample was compacted into a disk, and installed into an oxygen concentration cell. The oxygen concentration cells using the resulting disks of BiMeVOx, especially Me = Cu, were found to work as an oxygen sensor fairly well at 700 °C: the number of reaction electrons (n) associated with the reduction of O2was close to the theoretical one (4). With lowering operating temperature, however, the O2-responding properties degraded rather quickly: it was far larger at 500 °C. Such degradation was confirmed to be owing to decrease the rate of electrode reactions through the measurement of Faraday efficiency of oxygen pumping current. As a result, the performances of the cells were found to depend very much on the kinds of electrode materials. The use of a perovskite-type oxide, La0.6Sr0.4Co0.8Fe0.2O3, instead of Pt as a electrode was found to enable the cell to work at 400 °C and above. © 2005 Elsevier B.V. All rights reserved.
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Preparation of BiMeVOx (Me = Cu, Ti, Zr, Nb, Ta) compounds as solid electrolyte and behavior of their oxygen concentration cells
共著者：H. S. Cho, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 109, 307-314 (2005). 109 307 - 314 2005.9
Language：English Publishing type：Research paper (scientific journal)
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Behavior of oxygen concentration cells using BiCuVOx oxide-ion conductor
Cho H., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 108 ( 1-2 SPEC. ISS. ) 335 - 340 2005.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
The mixed oxide, Bi2Cu0.1V0.9O5.35often abbreviated as BiCuVOx, is known as an oxide-ionic conductor. The applicability of this oxide to a potentiometric oxygen sensor was investigated. Oxygen concentration cells were fabricated by using a disk of this oxide to test the EMF response to changes in oxygen concentration between 10% and 100% at various temperatures between 300 and 700 °C. As a result, the performances of the cells were found to depend very much on the kinds of electrode materials. When attached with Pt electrodes, the cell produced the EMF response fairly good only at 600 °C and above, whereas the oxide-ion transport number was close to unity even at 500 °C as evaluated from the Faraday efficiency of oxygen pumping current. The use of a perovskite-type oxide (La0.6Sr0.4Co0.8Fe0.2O3) instead of Pt was found to enable the cell to work at 400 °C and above. Especially excellent performances were observed when the oxide was mixed with BiCuVOxpowder prior to being applied on the BiCuVOxdisk as the electrodes. © 2004 Elsevier B.V. All rights reserved.
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Development of SnO<inf>2</inf>-based gas sensor sensitive to dilute ethylene oxide in air
Kugishima M., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 108 ( 1-2 SPEC. ISS. ) 130 - 133 2005.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
In order to enhance sensitivity to C2H4O for the medical safety purpose, foreign additives (e.g. La2O3, SrO and CaO) were loaded on SnO2powder. Among the additives tested, La2O3proved itself to be a promising promoter for the sensitivity. On the other hand, the response and recovery rates were found to be deteriorated with La2O3. The rates were accelerated considerably when the La2O3-loaded SnO2was further added with Pd or Pt. The device using Pt (0.5 wt.%)-La2O3(0.5 wt.%)-SnO2thus prepared showed sensor response exceeding 10 to 1 ppm C2H4O as well as fairly good response rates under dry condition at 300 °C, where response was defined as the resistance ratio (Rair/Rgas). © 2004 Elsevier B.V. All rights reserved.
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Miyachi Y., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 108 ( 1-2 SPEC. ISS. ) 364 - 367 2005.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A planar type CO2sensor device using NASICON (Na+conductor, Na3Zr2Si2PO12) thick film was attached with a glass (SiO2:Na2O:B2O3:Al2O3= 44:20:31:5, in molar ratio)-coated Na0.6CoO2reference electrode to increase its feasibility under various conditions in practical. The fabricated device proved satisfactory CO2-sensing properties at steady operating temperature (450 °C) under dry and humid conditions. In the heat-cycle tests between the operating temperature and room temperature under various humid conditions, the planar device once aged, exhibited quick warm-up characteristics and well-reproducible EMF response to CO2unless humidity was very high (e.g. 80%). © 2004 Elsevier B.V. All rights reserved.
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Development of SnO2-based gas sensor sensitive to dilute ethylene oxide in air Reviewed
共著者：M. Kugishima, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 108, 130-133 (2005). 108 130 - 133 2005.7
Language：English Publishing type：Research paper (scientific journal)
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Behavior of oxygen concentration cells using BiCuVOx oxide-ion conductor
共著者：H. Cho, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 108, 335-340 (2005). 108 335 - 340 2005.7
Language：English Publishing type：Research paper (scientific journal)
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Improvement of warming-up characteristics of potentiometric CO2 sensor by using solid reference counter electrode Reviewed
共著者：Y. Miyachi, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 108, 364-367 (2005). 108 364 - 367 2005.7
Language：English Publishing type：Research paper (scientific journal)
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Sensing properties of Au-loaded SnO2-Co3O4 composites to CO and H2 Reviewed
共著者：U.-S. Choi, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 107, 397-401 (2005). 107 397 - 401 2005.6
Language：English Publishing type：Research paper (scientific journal)
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Sensing properties of Au-loaded SnO2-Co3O4 composites to CO and H2
Choi U., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 107 ( 1 SPEC. ISS. ) 397 - 401 2005.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Two kinds of SnO2-Co3O4composites, SC1 and SC50, the Co3O4contents of which were 1 and 50 mass%, respectively, were loaded with small amounts of Au (0.05, 0.5 and 1 mass%). The thick film device using SC1, characterized by high sensitivity to both CO and H2at 250 °C, was found to be made more sensitive without significant alterations of selectivity between CO and H2as the amount of Au-loaded increased up to 0.5%, while the addition of 1 mass% Au degraded the sensing properties seriously. Similar promoting effects of Au were recognized for the SC50-based devices, which were p-type semiconductors responding fairly selectively to CO over H2at 100 °C. The promoting effects of Au were discussed briefly based on the behavior of electrical resistances of the Au-loaded devices. © 2004 Elsevier B.V. All rights reserved.
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Vuong D., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 105 ( 2 ) 437 - 442 2005.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Sols of crystalline SnO2with different mean grain (crystallite) sizes between 6 and 16 nm were prepared by subjecting stannic acid gel to hydrothermal treatments under various conditions. Thin film sensor devices with different film thicknesses between 200 and 900 nm were fabricated to investigate sensing properties to H2S gas. It was found that the sensor response to H2S, defined as the ratio of resistance in air to that in H2S-containing air, was greatly enhanced with decreasing film thick and with increasing grain size up to 16 nm, as expected from the gas diffusion-reaction theory. The response was surprisingly large, exceeding 104at 150 °C, for the device deposited with a 200 nm-thick film of SnO212 nm in grain size. © 2004 Elsevier B.V. All rights reserved.
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Hydrogen sulfide gas sensing properties of thin films derived from SnO2 sols different in grain size Reviewed
共著者：D. D. Vuong, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 105 (2), 437-442 (2005). 105 ( 2 ) 437 - 442 2005.3
Language：English Publishing type：Research paper (scientific journal)
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mori hiroshi, uota Masafumi, Fujikawa Daisuke, Yoshimura Takumi, Sakai Go, Kijima Tsuyoshi, Kuwahara Takeshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2005 ( 0 ) 295 - 295 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
having mesopores of 6-8 nm in pore-to-pore distance (The pore-size distribution obtained by N2 adsorption-desorption isotherm is 5 nm)and micropores of about 0.4nm in size.
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Synthesis and Luminessence properties of Eu(_III_)-Doped Y<SUB>2</SUB>O<SUB>2</SUB>SO<SUB>4</SUB>
Shinbori Tomohiro, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2005 ( 0 ) 300 - 300 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Morphologically controlled synthesis of nanocarbons from resorcinol-based nanopolymers
Fujikawa Daisuke, Uota Masafumi, Yoshimura Takumi, Sakai Go, Kijima Tsuyoshi
日本セラミックス協会 年会・秋季シンポジウム 講演予稿集 2005 ( 0 ) 617 - 617 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人 日本セラミックス協会
Much attention has been paid to the synthesis of inorganic nanomaterials by the sol-gel method combined with organic templating approach. Polymerization of resorcinol and formaldehyde (R-F) proceeds through the sol-gel process similar to that for metal alkoxide. This motivated us to apply the surfactant approach to the R-F system. Here we report the synthesis of rope-like, spherical and wire-like polymer particles as well as their conversion into carbons with essentially the same morphologies.
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Oxygen reduction properties of spongy platinum nanosheets loaded carbon
Sakai Go, Isohata Shusaku, Yoshimura Takumi, Kuwahara Takeshi, Uota Masafumi, Kawasaki Hideya, Kijima Tsuyoshi
日本セラミックス協会 年会・秋季シンポジウム 講演予稿集 2005 ( 0 ) 253 - 253 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人 日本セラミックス協会
Recently, our research group found that spongy platinum nanosheets are obtained by reducing Pt salts with sodium boron hydride (SBH) within mixed-surfactant liquid crystal templates. In this study, an attempt was made to load such Pt nanosheets on carbon-support with keeping the nano-structure. Electrochemical study revealed that the spongy Pt nanosheets loaded carbon has large electrochemically active surface area of Pt, and fairly high in electrochemical oxidation and reduction activity. Especially, the observed oxygen reduction activity was higher than that of commercially available ones.
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Synthesis of nanocarbons from morphologically controlled resorcinol-based nanopolymers
Fujikawa Daisuke, Uota Masafumi, Yoshimura Takumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2005 ( 0 ) 390 - 390 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Sakai Go, Nakatani Tomoe, Masaki Takanori, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2005 ( 0 ) 701 - 701 2005
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
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Stabilization of counter electrode for nasicon based potentiometric CO 2 sensor
Miyachi Y., Sakai G., Shimanoe K., Yamazoe N.
Ceramic Engineering and Science Proceedings 25 ( 3 ) 471 - 476 2004.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Engineering and Science Proceedings
Two kinds of materials, Bi2Cu0.1V0.9O 5.35 (BICUVOX) and NaCoO2, were investigated for their applicability as the counter electrode for a potentiometric CO2 sensor using NASICON (Na+ conductor, Na3Zr 2Si2PO12). The BICUVOX counter electrode was more stable than an Au counter electrode. Thermal cycling between the operating temperature (450°C) and room temperature under various conditions indicated the time needed for the BICUVOX electrode to reach the stationary potential after switching to the operating temperature was unacceptably long. NaCoO 2 was found unsuitable as a counter electrode material due to its reactivity with CO2. This reactivity was suppressed completely when NaCoO2 was coated with a layer of glass (SiO2: Na 2O: B2O3: Al2O3 = 44:20:31:5, in molar ratio). The glass-coated NaCoO2 electrode worked well as a counter electrode at 450°C. Thermal cycling indicated that the glass-coated NaCoO2 electrode exhibited an initial ageing effect. Once aged, glass-coated NaCoO2 showed the properties of a reliable counter electrode, i.e., rapid warm-up characteristics and a reproducible stationary potential at 450°C.
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Microstructural control of SnO2 thin films by using polyethylene glycol-mixed sols
Sakai G., Shimanoe K., Yamazoe N., Sato C.
Ceramic Engineering and Science Proceedings 25 ( 3 ) 477 - 482 2004.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Engineering and Science Proceedings
Microstructural control of SnO 2 thin films was attempted by introducing various amounts of polyethylene glycol (PEG) into an aqueous sol of SnO 2 to be spin-coated. As measured for the powder samples derived from the sols, the addition of PEG cut the specific surface area of SnO 2 almost in half, while keeping the crystallite size almost unchanged. Pore size distribution analysis revealed that the average pore diameter was about 6 nm for the powder derived from the neat SnO 2 sol, while it was enlarged to about 20 nm by the addition of PEG1000 by 18 wt%. SEM observation of spin-coated thin films revealed that morphology changed from a dense packing of very fine particles to a more porous packing of larger particles with the addition of PEG1000 or PEG6000. The thickness of spin-coated film could be increased by increasing amount of PEG1000 or PEG6000 added. The sensor response of these films to H 2 gas increased with increasing film thickness. This tendency is considered to result because the porous structure of the film becomes better developed as the amount of PEG increases.
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Yuasa M., Sakai G., Shimanoe K., Teraoka Y., Yamazoe N.
Journal of the Electrochemical Society 151 ( 10 ) 2004.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society
La1-xSrxMn0.8Fe0.2O 3+δ (x = 0-0.4) and La0.8Sr0.2Mn 1-yFeyO3+δ (y = 0-0.8) supported on carbon were successfully prepared by a reverse micelle method. Aqueous solutions dissolving nitrates of constituent metals of the intended oxides and tetramethylammonium hydroxide (precipitant) were separately transformed into reverse micelle dispersions by using poly(oxyethylene)5-lauryl ether (surfactant) and cyclohexane (oil). These dispersions were mixed together to derive a reverse micelle dispersion containing mixed hydroxides as precursors of the oxides, into which carbon powder suspended in cyclohexane was put under agitation. The suspension was destabilized with ethanol, and the resulting precipitate (carbon-supported precursors) was calcined in N2 atmosphere to prevent the carbon matrix from being combusted. Single-phase oxides supported on carbon were obtained by calcination at 700°C unless the oxides were free of Fe. Oxygen reduction activity of the gas-diffusion-type electrodes fabricated with thus prepared carbon-supported oxides increased sharply and decreased gradually with increasing x and y, respectively. Among the prepared oxides, the greatest activity, i.e., 500 mA/cm2 at -67 mV (vs. Hg/HgO electrode) in 9 M NaOH at 85°C under O2 flow, was achieved by the oxide with x = 0.4 and y = 0.2. Optimal loading on carbon as well as durability under oxygen reduction conditions were tested for selected oxides. 17 wt % La0.6Sr0.4Mn0.8Fe 0.2O3+δ loading electrode was compared with 27.7 wt % Pt-loading electrode in an oxygen reduction activity, and it was found that the former electrode was better than the Pt loading electrode. © 2004 the electrochemical society All rights reserved.
DOI： 10.1149/1.1789156
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Stabilization of counter electrode for NASICON based potentiometric CO2 sensor Reviewed
共著者：Y. Miyachi, G. Sakai, K. Shimanoe, N. Yamazoe
Ceramic Engineering and Science Proc., 25 (3), 471-476 (2004). 25 ( 3 ) 471 - 476 2004.11
Language：English Publishing type：Research paper (international conference proceedings)
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Microstructural control of SnO2 thin films by using polyethylene glycol-mixed sols Reviewed
共著者：G. Sakai, C. Sato, K. Shimanoe, N. Yamazoe
Ceramic Engineering and Science Proc., 25 (3), 477-482 (2004). 25 ( 3 ) 477 - 482 2004.11
Language：English Publishing type：Research paper (international conference proceedings)
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Exploration of reverse micelle synthesis of carbon-supported LaMnO <inf>3</inf>
Yuasa M., Sakai G., Shimanoe K., Teraoka Y., Yamazoe N.
Journal of the Electrochemical Society 151 ( 9 ) 2004.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society
Reverse micelle (RM) based synthesis of carbon-supported perovskite type oxide (LaMnO3) was investigated. By using cyclohexane as oil phase, six kinds of nonionic surfactants were tested for the formation of the revere micelle dispersions containing aqueous solutions of mixed nitrates of La 3+ and Mn2+ (RM-N) and tetramethylammonium hydroxide (RM-A) at the water/surfactant molar ratio (Rw) of 3. RM-A was found to be more difficult to form compared with RM-N or the RM containing pure water. At a temperature range of 5-25°C, it was given only by the surfactants with hydrophilic-lipophilic balance (HLB) values of 10.0-10.9. Phase diagrams of oil-surfactant-alkaline solution (or pure water) were constructed at 5 and 15°C for the best two surfactants, i.e., poly-(oxyetylene) 6-nonylphenyl ether and poly-(oxyetylene)5-lauryl ether. Mixing RM-N and RM-A together gave the RM containing a mixed hydroxides-precursor (RM-P), which was further converted into carbon-supported LaMnO3 through a series of treatments including the addition of carbon powder and calcination in N2 atmosphere at 600°C. The size of RM-P as well as that of the LaMnO3 grains supported on carbon could be controlled well by selecting Rw. The carbon-supported LaMnO3 proved to be highly active for the electrochemical reduction of oxygen. © 2004 The Electrochemical Society. All rights reserved.
DOI： 10.1149/1.1782165
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Ruiz A., Sakai G., Cornet A., Shimanoe K., Morante J., Yamazoe N.
Sensors and Actuators, B: Chemical 103 ( 1-2 ) 312 - 317 2004.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Nanocrystalline titanium dioxide with enhanced thermal stability was prepared by subjecting the alkoxide-derived TiO2gel to a hydrothermal treatment at 150°C for 3h in dilute HNO3solution (pH 3 or 2). Structural modifications of TiO2were analyzed by XRD and the morphology of the powders observed by FE-SEM. The hydrothermal treatment stabilized TiO2in two ways, i.e., suppressing thermal growth of TiO2crystallites and shifting up the temperature of anatase-to-rutile phase transformation, although the degree of stabilization differed considerably depending on the pH of the HNO3solution used. The TiO2hydrothermally treated at pH 3 consisted of small anatase nanospheres of 13 and 34nm in average diameter after calcination at 600 and 800°C, respectively, whereas the untreated TiO2was predominated by rutile phase at 700°C. Suppression of crystallite growth was even more conspicuous with the treatment at pH 2; the average crystallite size of anatase was 11 and 26nm after calcined at 600 and 800°C, respectively. In this case, however, the transformation was less hindered, with rutile phase occupying 9, 22 and 67% of TiO2after calcinations at 600, 700 and 800°C, respectively. This indicates that the phase transformation is not always related uniquely with crystallite size of anatase phase. The thick films fabricated with these TiO2powders did not show much differences in sensor response (ratio of resistance in air to that in gas) to dilute CO in air at 400-550°C, though the powder hydrothermally treated at pH 3 tended to give the highest response. However, the hydrothermal treatment was found to improve much the sensor response transients, suggesting that it was effective in developing mesopores inside the films. © 2004 Elsevier B.V. All rights reserved.
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Vuong D., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 103 ( 1-2 ) 386 - 391 2004.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Colloidal dispersions of crystalline SnO2(sols) with a mean grain (crystallite) size controlled between 6 and 16nm were prepared successfully from stannic acid gel by hydrothermal treatments under the condition of pH 10.5 and 200°C or pH 12.2 and 250°C. The growth of crystallites saturated in a few hours of hydrothermal treatment and the saturation values tended to increase with increasing SnO2gel content, pH and temperature. The SnO2grains remained monodispersed unless time of hydrothermal treatment was excessive. Thin films of SnO2prepared on an alumina substrate from the sols by a spin-coating method responded sharply to H2gas. The magnitude of sensor response as well as its dependence on operating temperature were different significantly depending on the grain sizes of the starting sols. Among the sols with a mean grain size of 6, 8.5, and 10nm, the last two gave large response to H2, which reached a maximum at 400 or 350°C, respectively. © 2004 Published by Elsevier B.V.
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Development of FET-type CO<inf>2</inf>sensor operative at room temperature
Shimanoe K., Goto K., Obata K., Nakata S., Sakai G., Yamazoe N.
Sensors and Actuators, B: Chemical 102 ( 1 ) 14 - 19 2004.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
An FET-type CO2sensor operative at room temperature was developed by stacking a powder mixture of metal carbonate (auxiliary phase) - indium tin oxide (ITO, sensing electrode) as well as Na+-exchanged cation exchange membrane (ionic conductor gate) on an FET chip. Both ITO and the cation exchange membrane were indispensable to obtain stable response to CO2at room temperature, while the auxiliary phase was optimized to be Li2CO3-BaCO3(1:3 in molar ratio) from the stability of response against the disturbance by humidity. The device, Li2CO3-BaCO3-ITO (1:3:1)/Na+-exchanged cation exchange membrane/FET, exhibited excellent CO2-sensing characteristics at 30°C. The response in gate-source voltage (VGS) was linear to the logarithm of CO2concentration, with its slopes indicating n = 2.0 where n is the number of reaction electrons involved in the electrochemical reduction per CO2. The Nernst's correlation was fairly stable against a change in RH between 30 and 70%. The times for 90% response and 90% recovery to switching-on and -off 3000 ppm CO2were 1 and 2 min, respectively. © 2004 Elsevier B.V. All rights reserved.
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Reverse Micelle-Based Preparation of carbon-supported La1-xSrxMn1-yFeyO3+d for Oxygen Reduction Electrode Reviewed
共著者：M. Yuasa, G. Sakai, K. Shimanoe, Y. Teraoka, N. Yamazoe
Journal of the Electrochemcal Society, 151, A1690-A1695 (2004). 151 1690 - 1695 2004.9
Language：English Publishing type：Research paper (scientific journal)
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Exploration for reverse micelle synthesis of carbon-supported LaMnO3 Reviewed
共著者：M. Yuasa, G. Sakai, K. Shimanoe, Y. Teraoka, N. Yamazoe
Journal of the Electrochemcal Society, 151, A1477-A1482 (2004). 151 1477 - 1482 2004.9
Language：English Publishing type：Research paper (scientific journal)
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Preparation of grain size-controlled tin oxide sols by hydrothermal treatment for thin film sensor application
共著者：D. D. Vuong, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, 103, 386-391 (2004). 2004.9
Language：English Publishing type：Research paper (scientific journal)
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Microstructure control of thermally stable TiO2 obtained by hydrothermal process for gas sensors Reviewed
共著者：A. M. Ruiz, G. Sakai, A. Cornet, K. Shimanoe, J. R. Morante, N. Yamazoe
Sensors and Actuators B, 103, 312-317 (2004). 103 312 - 317 2004.9
Language：English Publishing type：Research paper (scientific journal)
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Development of FET-type CO2 sensor operative at room temperature Reviewed
共著者：K. Shimanoe, K. Goto, K. Obata, S. Nakata, G. Sakai, N. Yamazoe
Sensors and Actuators B, Vol. 102, 14-19 (2004). 102 14 - 19 2004.9
Language：English Publishing type：Research paper (scientific journal)
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Wet process-based fabrication of WO<inf>3</inf>thin film for NO<inf>2</inf>detection
Choi Y., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 101 ( 1-2 ) 107 - 111 2004.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
It was tried to fabricate a WO3thin film device through a wet process starting from an aqueous sol of WO3·2H2O. When mixed with polyethylene glycol (PEG, molecular weight 6000), the sol was made compatible to spin coating on an alumina substrate and the coating could be converted into a WO3thin film by calcination at 300°C for 2h. Starting with a typical coating dispersion containing WO3·2H2O by 5mass% on WO3basis and 2mass% PEG, the WO3film obtained was 450nm in mean thickness. The film was a slim pack of square plates, each of which was a stack of thin lamellar crystals of WO3. The device was sensitive enough to detect 50ppb NO2in air at 200 or 250°C, although the response and recovery transients were rather sluggish. Unexpectedly, the transients were found to be sharpened drastically in humid atmosphere, while sensor response (sensitivity) to NO2was hardly degraded with humidity. © 2004 Elsevier B.V. All rights reserved.
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Wet process-based fabrication of WO3 thin film for NO2 detection Reviewed
共著者：Y.-G. Choi, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 101, 107-111 (2004). 101 107 - 111 2004.6
Language：English Publishing type：Research paper (scientific journal)
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Sensing properties of SnO2-Co3O4 composites to CO and H2
Choi U., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 98 ( 2-3 ) 166 - 173 2004.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A series of SnO2-Co3O4composite thick films (about 10μm thick) containing 0-100% Co3O4by mass of the composites were prepared from the component oxides through mixing by ball-milling for 24h, screen-printing and sintering at 700°C for 3h. The composite films were found to exhibit n- or p-type response to CO and H2depending on the Co3O4contents of the composites. The n-type response was exhibited at 200°C or above by SnO2-rich composites (Co3O4content up to 5mass%). The sensor response to both CO and H2, defined as Ra/Rg, where Raand Rgare electrical resistances in air and gas, respectively, was promoted strongly by the addition of small amounts of Co3O4to SnO2, and the response at 250°C as correlated with the Co3O4contents went through a sharp maximum at 1mass% Co3O4. The p-type response, obviously originating from Co3O4(p-type), was exhibited at 200°C or below by the composites containing 25-100mass% Co3O4. Remarkably, sensor response to CO, defined as Rg/Ra, was larger with the 50% Co3O4composite than with the neat Co3O4, while the reverse was true for the response to H2. Thus fairly sensitive and selective detection of CO over H2was possible with the 50% Co3O4composite. The physical state of the composites and the mechanisms of promotion of n- and p-type response were discussed. © 2003 Elsevier B.V. All rights reserved.
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Sensing properties of SnO2-Co3O4 composites to CO and H2 Reviewed
共著者：U.-S. Choi, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 98, 166-173 (2004). 98 166 - 173 2004.3
Language：English Publishing type：Research paper (scientific journal)
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Reduction of platinum salts using mixed surfactant liquid crystal as a reaction medium
Kuwahara Takeshi, Uota Masafumi, Yoshimura Takumi, Karasima Takeshi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2004 ( 0 ) 631 - 631 2004
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
Previously we reported the synthesis of platinum nanotubes from mixed surfactant liquid crystal(SLC) templates. The present study demonstrates that the structural order of LC is templates largely affected by couter cation species added and their thermal hystories. The effect of these preparation conditions on the morphological properties of the reduced platinum is also reported.
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Synthesis of high surface area hydroxyapatite nanorods by a mixed surfactant templating method
Uota Masafumi, Arakawa Hiroshi, Kitamura Nana, Yoshimura Takumi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2004 ( 0 ) 466 - 466 2004
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
Precipitation of calcium phosphate from mixed surfactant liquid crystal templates lead to hydroxyapatite nanorods covered with calcium stearate. On calcination at 500 <sup>o</sup>C the rod particles were deorganized into hydroxyapatite with a surface area of as large as 360 m <sup>2</sup>g<sup>-1</sup>.
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Synthesis of Nanostructured Platinum by a Mixed Surfactant Templating Method
Yoshimura Takumi, Uota Masafumi, Fuzikawa Daisuke, Kuwahara Takeshi, Sakai Go, Kizima Tuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2004 ( 0 ) 23 - 23 2004
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
Recently, we found that platinum nanotubes are synthesized from mixed surfactant liquid crystal templates. A similar but a little modified templating method was applied to the reduction of metal salts to obtain sponge- and layer-like platinum with a primary particle diameter of several tens of nanometer.
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Mesoporous Silica Nanoblocks with microporous walls from Mixed-Surfactant Liquid-Crystal Templates
Mori Hiroshi, Uota Masafumi, Yoshimura Takumi, Fujikawa Daisuke, Kuwahara Takeshi, Sakai Go, Kijima Tsuyoshi
Preprints of Annual Meeting of The Ceramic Society of Japan<br>Preprints of Fall Meeting of The Ceramic Society of Japan 2004 ( 0 ) 518 - 518 2004
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Ceramic Society of Japan
Mesoporous silica nanoblocks with microporous walls were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) using the mixed-surfactant liquid-crystal templates composed of nonaethylene-glycol monododecyl ether (C12EO9), polyoxyethylene (20) sorbitan monostearate (Tween60) and water, followed by the calcination of the resulting silica/surfactant nanocomplexes. The precursory LC was structurally characterized by X-ray diffraction. It was also found that the ethanol species formed by hydrolysis must be extracted with a large excess of water for the complexation.
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Controlled crystallization of ordered mesoporous anatase-based oxides
Li Donglin, Zhou Haoshen, Honma Itaru, Sakai Go, Kijima Tsuyoshi
日本セラミックス協会 年会・秋季シンポジウム 講演予稿集 2004 ( 0 ) 503 - 503 2004
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：公益社団法人 日本セラミックス協会
A methodology was developed to synthesize crystalline mesoporous metal oxides by help of controlled crystallization process. The proposed methodology has three essential features: (1) Mesoscopically ordered hybrids consisting of multicomponent inorganic precursors and surfactant templates can be obtained by using self-assembly procedure; (2) Subsequent in-situ crystallization of the materials through heat treatment transforms the hybrid into nanocrystal–based oxides; (3) Glass phase is used to control the crystallization. In this way, the nanocomposite consisting of anatase nanocrystals and glass phase can be designed and synthesized. In addition, almost fully crystalline mesoporous oxides can be resulted by decreasing the content of glass phase.
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Ultrasensitive gas sensor using Co3O4-modified SnO2
Choi U., Sakai G., Shimanoe K., Yamazoe N.
Ceramic Engineering and Science Proceedings 24 ( 4 ) 101 - 106 2003.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ceramic Engineering and Science Proceedings
SnO2 powder was loaded with 0-5 % Co3O4 by mass by a ball milling method. The resulting composites were screen printed onto a substrate to test the sensing properties to CO and H2. It was found that the sensor response, defined as the ratio of electrical resistance in air to that in gas, was greatly promoted with 0.5 or 1.0 % Co 3O4 loading, while further loadings (3 or 5 %) gave an adverse effect. For the 1 % Co3O4-loaded device, for example, the responses to 100, 50 and 10 ppm CO in air were as large as 375, 181 and 23 at 250 °C, respectively, and those to 50, 10 and 1 ppm H 2 in air were 568, 181 and 53 at 300 °C, respectively. The electrical resistance in air increased significantly with increasing Co 3O4 loading, indicating an electronic interaction between Co3O4 and SnO2. The change of the electronic interaction with a change in the redox state of Co3O4 appears to be an origin of the ultra high sensitivity to CO and H2.
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Matsunaga N., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 96 ( 1-2 ) 226 - 233 2003.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
In response and recovery steps of a thin film semiconductor gas sensor, target gas molecules diffuse in and out of the thin film. The gas diffusion dynamics taking place in these steps have been formulated based on a simple reaction-diffusion equation assuming a first-order reaction of target gas. In order to facilitate mathematical treatments, the actual thin film device was replaced by an equivalent model, for which boundary conditions could be set properly. With this model, the reaction-diffusion equation could be solved by using the methods of Fourier expansion and separation of variables. The solutions given as a function of diffusion coefficient D, rate constant k, film thickness L, depth x and time t, are shown to express well how target gas concentration profile in the thin film develops or vanishes in the response or recovery step, respectively. © 2003 Elsevier B.V. All rights reserved.
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Formulation of gas diffusion dynamics for thin film semiconductor gas sensor based on simple reaction-diffusion equation Reviewed
共著者：N. Matsunaga, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 96, 226-233 (2003). 96 226 - 233 2003.11
Language：English Publishing type：Research paper (scientific journal)
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Wet process-prepared thick films of WO<inf>3</inf>for NO<inf>2</inf>sensing
Choi Y., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 95 ( 1-3 ) 258 - 265 2003.10
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Preparation of an aqueous sol of WO3·2H2O starting from Na2WO4through an ion-exchange method, coupled with post-treatments (ultrasonic and/or centrifugal), was found to give WO3·2H2O gels which differed in morphology and preferred orientation depending on the kinds and conditions of the post-treatments. The morphology of the gels was well inherited topotaxically by the dehydrated phases of WO3·H2O and tungsten trioxide (WO3), allowing to control the morphology of WO3by the wet processing. The WO3thick film devices, fabricated from the gels and calcined at 300°C, were found to show very different sensor responses to NO2in air depending on the morphology of WO3. That is, poorly developed, small lamellas of WO3obtained by the ultrasonic treatment for a prolonged time (5h) gave the most sensitive device at 200°C, which could respond to as low as 10ppb NO2, while well developed, thin lamellas of WO3obtained by the centrifugal treatment for a prolonged time (10h) gave the most sensitive one at 300°C. In order to understand the dependence of sensor response on the morphology of WO3, several other methods were also adopted for preparing WO3. It was found that all of the sensor response data collected at 300°C could be related fairly well with the thickness of WO3lamellas or the diameter of WO3grains, whereas such a relationship became less certain at 200°C. © 2003 Elsevier Science B.V. All rights reserved.
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Wet process-prepared thick films of WO3 for NO2 sensing Reviewed
共著者：Y.-G. Choi, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 95, 258-265 95 258 - 265 2003.10
Language：English Publishing type：Research paper (scientific journal)
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Cr-doped TiO2 gas sensor for exhaust NO2 monitoring
Ruiz A., Sakai G., Cornet A., Shimanoe K., Morante J., Yamazoe N.
Sensors and Actuators, B: Chemical 93 ( 1-3 ) 509 - 518 2003.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A set of Cr-highly doped TiO2samples with Cr contents ranging from 5 to 30 at.% were prepared in a sol-gel route and calcined at a temperature between 600 and 900 °C. X-ray diffraction (XRD) analyses revealed the persistence of anatase phase up to the calcination temperature of 700 °C in all samples, above which rutile phase became dominant. The segregation of Cr2O3remained modest, only detectable by surface-sensitive technique like X-ray photoelectron spectra (XPS), for the 5 and 10 at.% Cr-doped samples calcined at 600 or 700 °C, suggesting incorporation of major part of doped Cr in the lattice of TiO2. Higher calcination temperatures or higher Cr contents lead to marked segregation of Cr2O3. XPS spectra in the valence band region of the samples calcined at 600 °C revealed a shift of the binding energy (BE) at the band edge to the lower energy side with increasing Cr contents, suggesting a tendency for the electronic conduction to alter from n- to p-type. As tested preliminarily, the thick and thin film devices prepared with these samples exhibited p-type conduction, and, particularly, a thin film device using 10 at.% Cr-doped sample calcined at 600 °C proved promising performances in the detection of dilute NO2in air at 500 °C. © 2003 Elsevier Science B.V. All rights reserved.
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Fabrication of CO2 sensor using NASICON thick film
Miyachi Y., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 93 ( 1-3 ) 250 - 256 2003.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
The condition of screen-printing paste was explored to densify a thick film of Na+conductor, Na3Zr2Si2PO12(NASICON) deposited on an alumina substrate. A fair well-densified NASICON thick film was found to be obtained from a paste consisting of NASICON powder and ethylene glycol dispersant by screen-printing and calcination at 1000 °C. The resulting planar sensor showed good CO2sensing capability even under humid conditions, although the emf tended to shift upward with increasing relative humidity. In order to reduce the disturbance by humidity, applicability of an oxide-ionic conductor of Bi2Me0.1V0.9O5.35as a counter electrode material was examined. The oxide-incorporated devices, of both disk type and planar, exhibited stable CO2sensing properties under dry as well as humid conditions. In addition, the dependence of emf on RH could be reduced considerably with the oxide-incorporated devices. It was found, however, that the RH dependence of emf originates from both of the sensing and counter electrodes so that the RH dependence of both electrodes should be tackled with to eliminate the RH dependence of the devices. © 2003 Elsevier Science B.V. All rights reserved.
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Preparation of size and habit-controlled nano crystallites of tungsten oxide
Choi Y., Sakai G., Shimanoe K., Teraoka Y., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 93 ( 1-3 ) 486 - 494 2003.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
An aqueous sol dispersing nano crystallites of WO3·2H2O was subjected to a centrifugal treatment for 1 or 10 h, to obtain two kinds of WO3·2H2O gels with very different morphology of crystals. The WO3thick film devices fabricated with these gels were investigated for several properties including NO2sensing characteristics. It was found that the devices prepared under proper conditions exhibited excellent NO2sensing properties to cover environmental standard of NO2. The sensitivity to NO2as well as the rate of response depended markedly on calcination temperature of the devices. The morphology of WO3crystals, i.e. lamellae or disks, was almost the same as that of WO3·2H2O gel unless calcination temperature exceeded 500 °C. Based on the surface analysis using N2adsorption technique, the above changes were estimated to result from a change in microstructure of the WO3crystals. © 2003 Elsevier Science B.V. All rights reserved.
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Fabrication of CO2 sensor using NASICON thick film Reviewed
共著者：Y. Miyachi, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 93, 250-256 93 250 - 256 2003.8
Language：English Publishing type：Research paper (scientific journal)
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Cr-doped TiO2 gas sensor for exhaust NO2 monitoring Reviewed
共著者：A. M. Ruiz, G. Sakai, A. Cornet, K. Shimanoe, J. R. Morante, N. Yamazoe
Sensors and Actuators B, Vol. 93, 486-494 93 486 - 494 2003.8
Language：English Publishing type：Research paper (scientific journal)
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Preparation of size and habit-controlled nano crystallites of tungsten oxide Reviewed
共著者：Y.-G. Choi, G. Sakai, K. Shimanoe, Y. Teraoka, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 93, 486-494 93 486 - 494 2003.8
Language：English Publishing type：Research paper (scientific journal)
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Oxide semiconductor gas sensors Reviewed
共著者：N. Yamazoe, G. Sakai, K. Shimanoe
Catalysis Surveys from Asia, Vol. 7, No.1, 63-75 7 ( 1 ) 63 - 75 2003.4
Language：English Publishing type：Research paper (scientific journal)
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Oxide semiconductor gas sensors
Yamazoe N., Sakai G., Shimanoe K.
Catalysis Surveys from Asia 7 ( 1 ) 63 - 75 2003.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Catalysis Surveys from Asia
Semiconductor gas sensors utilize porous polycrystalline resistors made of semiconducting oxides. The working principle involves the receptor function played by the surface of each oxide grain and the transducer function played by each grain boundary. In addition, the utility factor of the sensing body also takes part in determining the gas response. Therefore, the concepts of sensor design are determined by considering each of these three key factors. The requirements are selection of a base oxide with high mobility of conduction electrons and satisfactory stability (transducer function), selection of a foreign receptor which enhances surface reactions or adsorption of target gas (receptor function), and fabrication of a highly porous, thin sensing body (utility factor). Recent progress in sensor design based on these factors is described.
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Oxygen-sorptive and desorptive properties of perovskite-related oxides under temperature-swing conditions for oxygen enrichment Reviewed
共著者：H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Solid State Ionics, Vol. 152/153, 689-694 152/153 689 - 694 2002.12
Language：English Publishing type：Research paper (scientific journal)
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Kusaba H., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Solid State Ionics 152-153 689 - 694 2002.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Solid State Ionics
A group of A- and/or B-site partially substituted strontium cobaltites was investigated for oxygen-sorptive properties under temperature-swing conditions in air. The cobaltites with perovskite structure desorbed and absorbed significant amounts of oxygen quickly as well as reversibly on heating or cooling in the temperature range between 300 and 1000 °C, while those with brownmillerite or 2H-BaNiO3structure either lacked oxygen-sorptive properties or showed retarded oxygen sorption with hysteresis, respectively. Under temperature-swing cycles between 300 and 550 °C at a heating or cooling rate of 30 °C/min, SrCo0.4Fe0.6O3 - δshowed the largest mass change of 0.96%, or sorption and desorption of 7 cm3oxygen (STP)/g oxide among the perovskite-type oxides tested. This result appears to indicate the potential of a new oxygen enriching method coupled with a temperature-swing technique. © 2002 Published by Elsevier Science B.V.
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Choi Y., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 87 ( 1 ) 63 - 72 2002.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Aqueous sols of tungsten oxide dihydrate (WO3·2H2O) were prepared from Na2WO4by an ion-exchange method. An aqueous solution of Na2WO4was let to flow through a glass column packed with protonated cation-exchange resin. The effluent, initially transparent, turned into an opaque viscous fluid (pale yellow) in a few hours, before yellow precipitate deposited to completion in three days. The precipitate was a mixture of a crystalline phase of WO3·2H2O and an amorphous phase, and the crystalline part could be separated from another by washing with deionized water and centrifuging. The gel of WO3·2H2O thus obtained consisted of platelike crystallite 25nm thick and 42nm wide as evaluated from the X-ray diffractometer (XRD) peaks, and could be dispersed well into deionized water to form a stable suspension of colloidal particles with a mean diameter of about 30nm. The mean particle size as well as the crystallite size tended to increase gradually with the repetition of dispersion in water under ultrasonic wave agitation and gelling by centrifuging. On heating, the gel (WO3·2H2O) changed to the monohydrate (WO3·H2O) at 100°C, which in turn changed to the anhydride (WO3) at 240°C. Remarkably XRD patterns showed conspicuous preferred orientation of WO3·2H2O crystallites in (010) plane after the sol was centrifuged for a long time (10h) and, upon dehydration, it was inherited by the dehydrated phases, resulting in the conspicuous orientation of WO3crystallites in (001). © 2002 Elsevier Science B.V. All rights reserved.
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Preparation of aqueous sols of tungsten oxide dehydrate from sodium tungstate by an ion-exchange method Reviewed
共著者：Y. ?G. Choi, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Sensors and Actuators B,Vol. 87, 63-72 87 63 - 72 2002.11
Language：English Publishing type：Research paper (scientific journal)
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Preparation of Cr-doped TiO<inf>2</inf>thin film of p-type conduction for gas sensor application
Ruiz A., Cornet A., Sakai G., Shimanoe K., Morante J., Yamazoe N.
Chemistry Letters ( 9 ) 892 - 893 2002.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Titanium dioxide (TiO2) could be doped with as much as 8.7 atom% Cr by means of a sol-gel method. XRD analysis revealed that the powder of Cr (8.7 atom%)-doped TiO2calcined at 500°C consisted of small crystallites ascribale to anatase structure. The thin film of doped TiO2(70μm) at this composition was found to behave as a p-type semiconductor on exposure to CO and NO2in air: it responded to dilute NO2with a sharp decrease in electrical resistance.
DOI： 10.1246/cl.2002.892
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Preparation of Cr-Doped TiO2 Thin Film of p-type Conduction for Gas Sensor Application Reviewed
共著者：A. Ruiz, A. Cornet, G. Sakai, K. Shimanoe, J. R. Morante, N. Yamazoe
Chemistry Letters, No. 9, 892-893 9 892 - 893 2002.9
Language：English Publishing type：Research paper (scientific journal)
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Importance of Gas Diffusion in Semiconductor Gas Sensor
共著者：N. Yamazoe, G. Sakai, N. Matsunaga, N. -S. Baik, K. Shimanoe
Chemical Sensors for Hostile Environments Ceramic Transactions,Vol. 130, 27-36 130 27 - 36 2002.4
Language：English Publishing type：Research paper (scientific journal)
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Diffusion equation-based study of thin film semiconductor gas sensor-response transient
Matsunaga N., Sakai G., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 83 ( 1-3 ) 216 - 221 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A diffusion-reaction equation has been formulated and solved under non-steady condition in order to simulate how the gas concentration profile develops inside a thin film of semiconducting oxide after its exposure to a target gas. The gas concentration can be expressed by a polynomial function involving diffusion coefficient (D), rate constant (k), film thickness (L), depth from the film surface (x), time (t) and target gas concentration outside (Cs). Remarkably, the gas concentration at a given x exhibits overshooting behavior before reaching a steady value, the magnitude and appearance time of the overshooting being very dependent on x, k and L/D1/2. The overshooting appears as a result of the competition between diffusion and reaction. Two types of overshooting are recognized, which are ascribable to the gas molecules having entered from the surface and to those having reflected by the wall of substrate, respectively. Reflecting such an overshooting in gas concentration, the response transient also exhibits an overshooting phenomenon. © 2002 Elsevier Science B.V. All rights reserved.
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High temperature PTC thermistor using Ba cobaltite
Kinoshita K., Kusaba H., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Chemistry Letters ( 3 ) 412 - 413 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
It was found that partially Fe-substituted Ba cobaltite, BaCo0.7Fe0.3O3-δ, shows sharp PTC behavior at temperature above 850 °C. As revealed by XRD measurements, the PTC behavior is accompanied by phase transformation between hexagonal perovskite structure (low temperature) and cubic one (high temperature).
DOI： 10.1246/cl.2002.412
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Kinoshita K., Kusaba H., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Chemistry Letters ( 3 ) 344 - 345 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Oxygen permeation property of A-site partially substituted barium cobaltites, A′xBa1-xCo0.7Fe0.3O3-δ(A′ = Ba, Pr, Gd, Dy, Y and Yb), were examined. Substitution of Ba by Dy, Y or Yb was found to stabilize cubic perovskite structure even when x remained as small as 0.05. As a result, oxygen permeation through the disks made of these oxides appeared at temperature lower than 500 °C, and reached fairly high levels at elevated temperature.
DOI： 10.1246/cl.2002.344
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Miura N., Sasaki M., Sakai G., Vengatajalabathy Gobi K.
Chemistry Letters ( 3 ) 342 - 343 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
A regenerable surface plasmon resonance (SPR)-based immunosensor functioning with the indirect competitive immunoreaction of monoclonal antibody between the analyte (antigen) in testing solution and antigen-bovine serum albumin conjugate immobilized on immunoprobe provided a rapid in situ estimation (response time: about 15 min) of benzo(a)pyrene in the concentration range of 0.1-300 ppb.
DOI： 10.1246/cl.2002.342
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Temperature-swing based oxygen enrichment by using perovskite-type oxides
Kusaba H., Sakai G., Shimanoe K., Yamazoe N., Miura N.
Journal of Materials Science Letters 21 ( 5 ) 407 - 409 2002.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Materials Science Letters
A temperature-swing-adsorption method was established as a new oxygen-enriching method. The resulting method combines oxygen-absorptive properties of perovskite type oxides and waste heat from high temperature processes. The feasibility of the new method was explored using a family of partially substituted strontium cobaltites.
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Temperature-swing based oxygen enrichment by using perovskite-type oxides Reviewed
共著者：H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Journal of Materials Science Letters,Vol. 21, 407-409 21 407 - 409 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Diffusion equation-based study of thin film semiconductor gas sensor -response transient- Reviewed
共著者：N. Matsunaga, G. Sakai, K. Shimanoe, N. Yamazoe
Sensors and Actuators B, Vol. 83, 216-221 83 216 - 221 2002.3
Language：English Publishing type：Research paper (scientific journal)
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High Temperature PTC Thermistor Using Ba Cobaltite Reviewed
共著者：K. Kinoshita, H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Chemistry Letters, No.3, 412-413 ( 3 ) 412 - 413 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Influences of A-site Partial Substitution for BaCo0.7Fe0.3O3 Oxide on Perovskite Structure and Oxygen Permeability Reviewed
共著者：K. Kinoshita, H. Kusaba, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Chemistry Letters, No.3, 344-345 3 344 - 345 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Regenerable surface plasmon resonance (SPR)-based immunosensor for highly sensitive measurement of sub-ppb levels of benzo(a)pyrene
共著者：N. Miura, M. Sasaki, G. Sakai, K. V. Gobi
Chemistry Letters, No.3, 342-343 2002 ( 3 ) 342 - 343 2002.3
Language：English Publishing type：Research paper (scientific journal)
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Theory of gas-diffusion controlled sensitivity for thin film semiconductor gas sensor
Sakai G., Matsunaga N., Shimanoe K., Yamazoe N.
Sensors and Actuators, B: Chemical 80 ( 2 ) 125 - 131 2001.11
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Influences of gas transport phenomena on the sensitivity of a thin film semiconductor gas sensor were investigated theoretically. A diffusion equation was formulated by assuming that an inflammable gas (target gas) moves inside the film by Knudsen diffusion, while it reacts with the adsorbed oxygen following a first-order reaction kinetic. By solving this equation under steady-state conditions, the target gas concentration inside the film was derived as a function of depth (x) from the film surface, Knudsen diffusion coefficient (DK), rate constant (k) and film thickness (L). The gas concentration profile thus obtained allowed to estimate the gas sensitivity (S) defined as the resistance ratio (Ra/Rg), under the assumption that the sheet conductance of the film at depth x is linear to the gas concentration there with a proportionality constant (sensitivity coefficient), a. The derived equation shows that S decreases sigmoidally down to unity with an increase in L√k/DK. Further by assuming that the temperature dependence of rate constant (k) and sensitivity coefficient (a) follows Arrenius type ones with respective activation energies, it was possible to derive a general expression of S involving temperature (T). The expression shows that, when the activation energies are selected properly, the S versus T correlation results in a volcano-shaped one, its height increasing with decreasing L. The dependence of S on L at constant T as well as on T at constant L can thus be simulated fairly well based on the equation. © 2001 Elsevier Science B.V. All rights reserved.
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Theory of Gas-diffusion Controlled Sensitivity for Thin Film Semiconductor Gas Sensor Reviewed
共著者：G. Sakai, N. Matsunaga, K. Shimanoe, N. Yamazoe
Sensors and Actuators B,Vol. 80, 125-131 80 125 - 131 2001.11
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Baik N., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 77 ( 1-2 ) 116 - 121 2001.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin film SnO2sensors with various thicknesses were spin-coated from a hydrothermally treated SnO2sol suspension. The FE-SEM observation revealed that the films prepared from the 1.8 wt.% SnO2containing sol suspension had good uniformity packed with nano-crystalline SnO2even after calcination at 600°C when its thickness was up to about 300 nm, though many cracks were observed for thicker films. The gas sensing characteristics to H2and CO were evaluated as a function of film thickness (80-300 nm) in dry air. The electrical resistance of thin films decreased monotonically with increasing film thickness. It was found that the sensor response to H2similarly decreased with an increase in film thickness, while the CO response was found to be almost independent of the film thickness. The relationship between gas sensing properties and film thickness was discussed on the basis of diffusivity and reactivity of the gases inside the oxide films. © 2001 Elsevier Science B.V.
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Metal oxide semiconductor N<inf>2</inf>O sensor for medical use
Kanazawa E., Sakai G., Shimanoe K., Kanmura Y., Teraoka Y., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 77 ( 1-2 ) 72 - 77 2001.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
In order to develop a semiconductor type gas sensor applicable to the monitoring of N2O in air, a search for the semiconducting oxides sensitive to N2O was carried out. Among the 23 kinds of single oxides tested, SnO2turned out to give the highest sensitivity to N2O, although the sensitivity was not high enough. The N2O sensitivity was found to be promoted effectively when SnO2was loaded with a small amount of a basic oxide such as SrO, CaO, BaO, Bi2O3and Sm2O3. The promotion was particularly conspicuous with SrO loading. For example, 0.5wt.% SrO-loaded SnO2, exhibited the N2O sensitivity about three times as high as that of pure SnO2, and could detect N2O in air fairly well in the concentration range of 10-300 ppm at 500°C. © 2001 Elsevier Science B.V.
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Metal Oxide Semiconductor N2O Sensor for Medical Use Reviewed
共著者：E. Kanazawa, G. Sakai, K. Shimanoe, Y. Kanmura, Y. Teraoka, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 77, 72-77 77 72 - 77 2001.6
Language：English Publishing type：Research paper (scientific journal)
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Gas sensing properties of tin oxide thin films fabricated from hydrothermally treated nanoparticles -Dependence of CO and H2 response on film thickness- Reviewed
共著者：G. Sakai, N. S. Baik, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 77, 116-121 77 116 - 121 2001.6
Language：English Publishing type：Research paper (scientific journal)
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Preparation of Stabilized Nano-size Tin-Oxide Particles by Hydrothermal Treatment Reviewed
共著者：N.-S. Baik, G. Sakai, N. Miura, N. Yamazoe
Journal of the American Ceramic Society, Vol. 83,No. 12, 2983-2987 83 ( 12 ) 2983 - 2987 2000.12
Language：English Publishing type：Research paper (scientific journal)
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Semiconductor Gas Sensor Using SrO-Modified SnO2 for the Detection of N2O in Air Reviewed
共著者：E. Kanazawa, G. Sakai, K. Shimanoe, Y. Kanmura, Y. Teraoka, N. Miura, N. Yamazoe
Electrochemical and Solid-State Letters, Vol. 3, No. 12, 572-574 3 ( 12 ) 572 - 574 2000.12
Language：English Publishing type：Research paper (scientific journal)
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Kanazawa E., Sakai G., Shimanoe K., Kanmura Y., Teraoka Y., Miura N., Yamazoe N.
Electrochemical and Solid-State Letters 3 ( 12 ) 572 - 574 2000.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrochemical and Solid-State Letters
A semiconductor-type sensor applicable to the monitoring of N2O in air was studied. As revealed by a screening test, n-type oxides such as SnO2, In2O3, WO3, and ZnO were more or less sensitive to N2O, while the highest sensitivity was obtained with SnO2. However, the N2O sensitivity of SnO2was not sufficient for practical application. The addition of SrO to SnO2was effective for improving N2O sensitivity. Thus 0.5 wt % SrO-SnO2was about three times as sensitive as pure SnO2, allowing good detection of 10-300 ppm N2O in air at 500 °C.
DOI： 10.1149/1.1391212
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糖尿病診断を目指した呼気中アセトン検出用薄膜型酸化物半導体ガスセンサ Reviewed
共著者：酒井 剛、元岡功一、三浦則雄、山添 曻
電気学会準部門誌E、Vol.-120-E,No. 10, 476-481 120-E ( 10 ) 476 - 481 2000.10
Language：Japanese Publishing type：Research paper (scientific journal)
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Hydrothermal treatment of tin oxide sol solution for preparation of thin-film sensor with enhanced thermal stability and gas sensitivity Reviewed
共著者：N.-S. Baik, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Sensors and Actuators B,Vol. 65, 97-100 65 97 - 100 2000.7
Language：English Publishing type：Research paper (scientific journal)
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Spin-coated indium oxide thin film on alumina and silicon substrates and their gas sensing properties Reviewed
共著者：W.-Y. Chung, G. Sakai, K. Shimanoe, N. Miura, D.-D. Lee, N. Yamazoe
Sensors and Actuators B, Vol. 65, 312-315 65 312 - 315 2000.7
Language：English Publishing type：Research paper (scientific journal)
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Phase Transformation and Oxygen Permeation Properties of Partially Substituted Strontium Cobaltite -Influences of B-site Partial Substitution- Reviewed
共著者： H. Kusaba, G. Sakai, N. Miura, N. Yamazoe
Ionics, Vol, 6, 47-56 6 47 - 56 2000.7
Language：English Publishing type：Research paper (scientific journal)
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Baik N., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 65 ( 1 ) 97 - 100 2000.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
The effects of treating tin oxide gel hydrothermally in an ammonia solution at 200 °C for 3 h were studied. The size of sol particles increased with increasing concentration of the resulting sol solution, i.e., 5, 8, 10 and 32 nm for 1.8, 3.2, 6.1 and 8.6 wt.% tin oxide sol as determined by an optical analyzer, whereas the crystallite size of tin oxide determined by X-ray diffraction analysis remained to be about 5-7 nm for all the solutions. The tin oxide powder collected was found to be resistant to grain growth on calcination, depending on the concentration of the sol solution. This tendency was maintained in the thin-films spin-coated on an alumina substrate from the sol solutions. The grain size of the film derived from 1.8 wt.% tin oxide sol was smaller than 10 nm in diameter after calcination at 600 °C. This particular film exhibited an outstanding by high sensitivity to 800 ppm H2at 350 °C, compared with conventional tin oxide elements of a sintered block type.
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Chung W., Sakai G., Shimanoe K., Miura N., Lee D., Yamazoe N.
Sensors and Actuators, B: Chemical 65 ( 1 ) 312 - 315 2000.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin films of indium oxide were prepared on alumina and silicon substrates by spin-coating from an aqueous acetic acid solution dissolving In(OH)3and ammonium carboxymethyl cellulose. The films could cover well the large grains of rough alumina as well as the flat surface of silicon. By changing the number of spin-coating, the film thickness was well controlled between 70 nm and 210 nm on alumina or between 65 nm and 220 nm on silicon, as observed by cross-sectional FE-SEM. Gas sensing properties including sensitivity, selectivity and the rates of response and recovery were strongly dependent on the kind of substrate, film thickness and operating temperature.
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Kusaba H., Sakai G., Miura N., Yamazoe N.
Electrochemistry 68 ( 6 ) 409 - 411 2000.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrochemistry
The relation between oxygen permeation and phase transformation of A- and B-site partially substituted strontium cobaltites, Sr0.9Ca0.1Co1-xB′xO2.5 + δ (B′= Co, Mn, Ni, In, Fe or Al), were examined. As analyzed by high-temperature XRD, all of these oxides transformed into perovskite-type structure at elevated temperatures. The transformation temperatures of the last two oxides (B′= Fe or Al) were lower than those of the others. Noticeably, the phase transformation temperatures coincided with the temperature at which oxygen permeation switched on. The lowest switching-on temperature (750°C) was observed with the Fe-substituted oxide among the above oxides.
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Oxygen Permeability and Phase Transformation of Strontium-Cobaltite System. -Effect of B-site Substitution
共著者：H. Kusaba, G. Sakai, N. Miura, N. Yamazoe
Electrochemistry, Vol. 68, No. 6, 409-411 68 ( 6 ) 409 - 411 2000.6
Language：English Publishing type：Research paper (scientific journal)
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Hydrothermally treated sol solution of tin oxide for thin-film gas sensor
Baik N., Sakai G., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 63 ( 1 ) 74 - 79 2000.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
A sol solution containing SnO2particles (crystallites) of 6 nm in average diameter was prepared by a hydrothermal treatment. The hydrothermal treatment was found to be very effective for suppressing the thermal growth of SnO2grains. A thin-film sensor device, fabricated by spin-coating from the sol solution, consisted of SnO2crystallites with 6 nm in mean diameter after calcination at 600 °C. The device proved for better properties in sensitivity and response transient than a conventional sintered-block sensor device using SnO2precipitated gel.
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Jinkawa T., Sakai G., Tamaki J., Miura N., Yamazoe N.
Journal of Molecular Catalysis A: Chemical 155 ( 1-2 ) 193 - 200 2000.4
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of Molecular Catalysis A: Chemical
A semiconductor gas sensor using SnO2was loaded with acidic or basic oxides (5 wt.%) to investigate ethanol-gas sensing properties and related catalytic properties. The sensitivity to ethanol gas at 300°C increased tremendously with an addition of a basic oxide (e.g., La2O3), while it hardly changed with that of an acidic oxide (WO3). It turned out that the addition of the basic metal oxide to SnO2brought about enhancement of catalytic activity not only for the dehydrogenation of ethanol gas to CH3CHO but also for the consecutive oxidation of CH3CHO to CO2. On the other hand, the acidic metal oxide enhanced only the dehydration reaction, showing even an adverse effect on the consecutive oxidation. Based on these results, it was concluded that the enhancement of the catalytic oxidation activity to an appropriate level could be a reason for the high sensitivity to ethanol gas for the sensors loaded with basic oxides, particularly one loaded with La2O3. (C) 2000 Elsevier Science B.V.
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Hydrothermally treated sol solution of tin oxide for thin-film gas sensor
共著者：N. ?S. Baik, G. Sakai, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 63/1-2, 73-79 63 ( 1-2 ) 73 - 79 2000.4
Language：English Publishing type：Research paper (scientific journal)
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Relationship between ethanol gas sensitivity and surface catalytic property of tin oxide sensors modified with acidic or basic oxides
共著者：T. Jinkawa, G. Sakai, J. Tamaki, N. Miura, N.Yamazoe
Journal of Molecular Catalysis A, Vol. 155(1-2), 193-200 2000.4
Language：English Publishing type：Research paper (scientific journal)
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Preparation of stabilized nanosized tin oxide particles by hydrothermal treatment
Baik N., Sakai G., Miura N., Yamazoe N.
Journal of the American Ceramic Society 83 ( 12 ) 2983 - 2987 2000.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the American Ceramic Society
Stable colloidal suspensions of tin oxide (content 0.9-6.1 wt%) were synthesized by subjecting conventionally prepared tin oxide gels to hydrothermal treatment with an ammonia solution (pH 10.5) at 200°C for 3 h in an autoclave. Based on X-ray diffractometry analyses, the tin oxide crystallites after hydrothermal treatment were resistant to thermal growth at elevated temperatures, and this feature became more conspicuous as the tin oxide content of the colloidal suspension decreased. For the powder derived from a 1.8 wt% colloidal suspension, for example, the mean sizes of the tin oxide crystallites were 7.5 and 13 nm after calcination at 600° and 900°C, respectively, in comparison with corresponding values of 13.5 and 29 nm for the untreated gel-derived powder. Thin film spin-coated from the same suspension had good uniformity, packed with tin oxide grains (crystallites) of a mean size of 6 nm after calcination at 600°C. Optical determination of the tin oxide sol particle size, as well as gravimetric analysis of the dehydration from the powder samples, were conducted to determine effects of hydrothermal treatment.
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Kusaba H., Sakai G., Miura N., Yamazoe N.
Ionics 6 ( 1-2 ) 47 - 56 2000.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Ionics
A group of B-site partially substituted stron.tium cobaltites Sr0.9Cao.1COo.9B'0.1O2.5+8(B'=Mn, Co, Ni, In, Fe and AI) were examined for phase transformation and oxygen permeation properties. As revealed by XRD analysis, these oxides had 2H-BaNiO3-type structure (B'=Mn, Co, Ni and In) or brownmillerite-type structure (B'=Fe and A1) and transformed into perovskite-type structure at elevated temperatures (750 °C or above). The transformation temperature was dependent on the B-site substituent and agreed well with the switching-on temperature of oxygen permeation for the same oxide. Due to a lowering in transformation temperature, the Fe- or Al-doped oxide was made oxygen permeable in the lower temperature range 750-850 °C where the undoped oxide remained non-permeable. It was also found that for a series of Fe-partially substituted samples Sr09Cao°CCol. °CFe°CO25+5the transformation temperature lowered with increasing x up to 0.1, while, for x ≥ 0.2, perovskite-type structure tended to be stabilized at room temperature. TGDTA analysis revealed that phase transformation was accompanied by absorption or desorption of oxygen. Based on the correlation between the oxygen permeability and the membrane thickness, the rate-determining step of oxygen permeation in the present system was assumed to be of the bulk diffusion of oxide ion vacancies.
DOI： 10.1007/BF02375546
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Sakai G., Motooka K., Miura N., Yamazoe N.
IEEJ Transactions on Sensors and Micromachines 120 ( 10 ) 476 - 481 2000
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Sensors and Micromachines
Thin-film-type oxide semiconductor gas sensors sensitive to acetone were explored for the diagnosis of diabetes. SnO2 and ZnO were tested as a base sensor material. When fabricated into a thick-film-type sensor, SnO2 was inferior to ZnO in the acetone sensitivity. However, on changing to a thin-film-type sensor, SnO2 proved to be more sensitive to acetone than ZnO. The acetone sensitivity of the SnO2-based thin film sensor could be improved by the addition (0.1 wt%) of noble metals, such as Rh and Ru. The resulting sensor using Rh-SnO2 could detect as dilute as 0.2 ppm acetone in human expiration at 300∘ without being disturbed by changes in O2 and CO2 concentrations. © 2000, The Institute of Electrical Engineers of Japan. All rights reserved.
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SPR免疫センサによるメタンフェタミン（覚醒剤）の高感度検出とその抗原抗体反応解析
共著者：中田聖士、酒井 剛、宇田泰三、三浦則雄、山添 曻
電気学会E部門誌、センサ・マイクロマシン部門誌、Vol. 119-E, 581-586頁 1999.11
Language：English Publishing type：Research paper (scientific journal)
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Oxygen permeability and phase transformation of Sr<inf>0.9</inf>Ca<inf>0.1</inf>CoO<inf>2.5+δ</inf>
Miura N., Murae H., Kusaba H., Tamaki J., Sakai G., Yamazoe N.
Journal of the Electrochemical Society 146 ( 7 ) 2581 - 2586 1999.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Journal of the Electrochemical Society
Oxygen permeation properties of Sr1-xA′xCoO2.5+δ (A′ = Ca, Sr, Ba, and Mg) were investigated. The oxides with x≤0.2 had hexagonal 2H-BaNiO3-type structure at room temperature. The disk membranes (1.0 mm thick) made of these oxides, when cooled from high temperature, showed significant rates of oxygen permeation down to critical temperatures characteristic of the kind of oxides, below which the rates sharply diminished. Among the oxides tested, Sr0.9Ca0.1CoO2.5+δ showed the largest rate (2.0 cm3 at standard temperature and pressure min-1 cm-2) at 900 °C. As indicated by the X-ray diffraction and thermogravimetry-differential thermal analysis, this oxide underwent phase transformation between the above structure (low-temperature phase) and a cubic perovskite structure (high-temperature phase), which were oxygen nonpermeable and oxygen permeable, respectively. On heating, the oxygen content (2.5+δ) of the oxide decreased in two steps, i.e., first from 2.75 to 2.6 over the temperature range 400 to 600 °C without changing the structure, and then from 2.6 to 2.5 at the temperature of transformation to the high-temperature phase (about 900 °C). The rate of oxygen permeation of the oxide at 900 °C was found to depend on the membrane thickness. Based on these results, oxygen permeation and its relevance to phase transformation are discussed.
DOI： 10.1149/1.1391975
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Oxygen permeability and phase transformation of Sr0.9Ca0.1CoO2.5+d Reviewed
共著者：N. Miura, H. Murae, H. Kusaba, J. Tamaki, G. Sakai, N. Yamazoe
Journal of Electrochemical Society, Vol. 146, No. 7, 2581-2586 146 ( 7 ) 2581 - 2586 1999.7
Language：English Publishing type：Research paper (scientific journal)
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Highly selective and sensitive SPR immunosensor for detection of methamphetamine
Sakai G., Nakata S., Uda T., Miura N., Yamazoe N.
Electrochimica Acta 44 ( 21 ) 3849 - 3854 1999.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Electrochimica Acta
Highly sensitive and selective detection of methamphetamine (MA) was realized by using an immunosensor based on surface-plasmon-resonance (SPR) phenomena. A methamphetamine-bovine serum albumin (MA-BSA) conjugate was prepared as an antigen. It was immobilized on the Au thin film of sensor chip by physical adsorption. The incident angle of the MA-BSA immobilized sensor increased with increasing concentration of anti-MA-BSA antibody up to ca. 20 μg/ml (ppm) and then almost saturated above this concentration. The addition of MA into the antibody solution (20 ppm) was found to decrease the incident angle shift sharply because of the inhibition effect of MA. The present sensor was confirmed to detect MA very sensitively in the concentration range of 0.1-1000 ng/ml (ppb). Moreover, it was found that the sensor could detect MA in the PBS solution containing 1% human urine without any significant changes in incident angle shift due to nonspecific adsorption. Furthermore, it was confirmed that the interference effect of methylephedrine on the MA sensitivity of the sensor was fairly small. From the correlation between incident angle shift and MA concentration, the affinity constants of anti-MA antibody to MA (in liquid media) and MA-BSA (immobilized) were evaluated by assuming Langmuir isotherm and equilibrium state of immunoreaction.
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Highly selective and sensitive SPR immunosensor for detection of methamphetamine
共著者：G. Sakai, S. Nakata, T. Uda, N.Miura, N. Yamazoe
Electrochimica Acta, Vol. 44/21-22, 3849-3854 1999.6
Language：English Publishing type：Research paper (scientific journal)
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Nakata S., Sakai G., Uda T., Miura N., Yamazoe N.
IEEJ Transactions on Sensors and Micromachines 119 ( 11 ) 581 - 586 1999
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Sensors and Micromachines
Highly sensitive detection of methamphetamine (MA) was realized by using an immunosensor based on surface plasmon resonance (SPR) phenomena. A methamphetamine-bovine serum albumin (MA-BSA) conjugate was prepared as an antigen, and it was immobilized on the Au thin film of sensor-chip. Introduction of MA into the antibody solution was found to decrease the incident angle shift sharply because of the inhibition effect of MA. Association constants between anti-MA antibody and MA as well as anti-MA antibody and MA-BSA were evaluated from the Langmuir isotherm adsorption model. The association constants between anti-MA antibody and MA or MA-BSA were estimated as 5.68×106M-1, 2.92×107 M-1 respectively. The association rate constant and dissociation rate constant were also estimated from typical transient responses to antibody solutions. © 1999, The Institute of Electrical Engineers of Japan. All rights reserved.
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Chung W., Sakai G., Shimanoe K., Miura N., Lee D., Yamazoe N.
Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 37 ( 9 A ) 4994 - 4998 1998.9
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Thin films of indium oxide were prepared on a silicon substrate by a spin-coating method using a coating solution dissolving In(OH)3, acetic acid and ammonium carboxymethyl cellulose. The films consisted of a dense stack of fairly uniform grains, adhering well to the substrate, as observed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The film thickness was well controlled by repeating the spin-coating. The sensing properties of the In2O3 film to CO, H2 and C3H8 depended on the film thickness and temperature, fairly good sensing performance to CO being achieved with a 140-nm-thick film at 350°C. The contact between platinum electrode and In2O3 in these devices was found to be slightly non-Ohmic, unlike that in the sintered block type device.
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酸化ビスマスを用いた半導体NOセンサ
共著者：酒井 剛、神川晃幸、三浦則雄、山添 曻
電気学会E部門誌、センサ・マイクロマシン部門誌、Vol. 118-E, 578-583頁 118-E 578 - 583 1998.9
Language：Japanese Publishing type：Research paper (scientific journal)
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A surface plasmon resonance-based immunosensor for highly sensitive detection of morphine
Sakai G., Ogata K., Uda T., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 49 ( 1-2 ) 5 - 12 1998.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Highly sensitive and selective detection of morphine (MO) based on surface-plasmon-resonance (SPR) was realized by using an anti-MO monoclonal antibody and MO-bovine serum albumin (MO-BSA) conjugate (antigen). MO-BSA was immobilized on the Au thin film of the SPR sensor chip by physical adsorption. The incident angle of the SPR system using the MO-BSA immobilized chip increased almost linearly with increasing concentration of antibody up to ca. 5 μg ml-1(ppm). The addition of MO to the antibody solution (5 ppm) was found to reduce the incident angle shift sharply because of the inhibition effect of MO. Based on this inhibiting principle, the present sensor could detect MO in the concentration range 0.1-10 ng ml-1(ppb). The affinity constants between the antibody and the antigens (MO and MO-BSA) could be obtained by assuming a Langmuir adsorption model for the immunoreaction system. © 1998 Elsevier Science S.A. All rights reserved.
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Gas sensing properties of indium oxide thin film on silicon substrate prepared by spin-coating method Reviewed
共著者：W.-Y. Chung, G. Sakai, K. Shimanoe, N. Miura, D.-D. Lee, N. Yamazoe
Japanease Journal of Applied Physics, Vol. 37, 4994-4998 37 4994 - 4998 1998.6
Language：English Publishing type：Research paper (scientific journal)
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Preparation of indium oxide thin film by spin-coating method and its gas-sensing properties
Chung W., Sakai G., Shimanoe K., Miura N., Lee D., Yamazoe N.
Sensors and Actuators, B: Chemical 46 ( 2-3 ) 139 - 145 1998.2
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin films of In2O3were fabricated on an alumina substrate by spin-coating of an aqueous solution prepared from In(OH)3, acetic acid and ammonium carboxymethyl cellulose, followed by drying at 110°C and calcining at 600°C. As observed by SEM, the films consisted of a dense stack of tiny In2O3particles (23-27 nm in diameter) and covered large grains of the alumina substrate well. Subsequently, film thickness was well controlled by the number of spin-coatings. Gas sensing properties were strongly dependent on the film thickness and temperature and fairly excellent sensing performances to H2, CO and C3H8were obtained with a 160 nm-thick film (5 times coated) at 350°C. © 1998 Elsevier Science S.A. All rights reserved.
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Surface Plasmon Resonance-Based Immunosensor for Highly Sensitive Detection of Morphine Reviewed
共著者：G. Sakai, K. Ogata, T. Uda, N. Miura, N. Yamazoe
Sensors and Actuators B,Vol. 49/1-2, 5-12 49 ( 1-2 ) 5 - 12 1998.2
Language：English Publishing type：Research paper (scientific journal)
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Preparation of indium oxide thin film by spin-coating method and its gas-sensing properties Reviewed
共著者：W.-Y. Chung, G. Sakai, K. Shimanoe, N. Miura, D.-D. Lee, N. Yamazoe
Sensors and Actuators B, Vol. 46/2, 139-145 46 ( 2 ) 139 - 145 1998.2
Language：English Publishing type：Research paper (scientific journal)
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Preparation of indium oxide thin film by spin-coating method and its gas-sensing properties
Chung W., Sakai G., Shimanoe K., Miura N., Lee D., Yamazoe N.
Sensors and Actuators, B: Chemical B46 ( 2 ) 139 - 145 1998.1
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin film of In2O3were fabricated on an alumina substrate by spin-coating of an aqueous solution prepared from In(OH)3, acetic acid and ammonium carboxymethyl cellulose, followed by drying at 110 °C and calcining at 600 °C. As observed by SEM, the films consisted of a dense stack of tiny In2O3particles (23-27 nm in diameter) and covered large grains of the alumina substrate well. Subsequently, film thickness was well controlled by the number of spin-coatings. Gas sensing properties were strongly dependent on the film thickness and temperature and fairly excellent sensing performances to H2, CO and C3H8were obtained with a 160 nm-thick film (5 times coated) at 350 °C.
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Bismuth Oxide-Based Semiconductor Gas Sensor for Nitrogen Monoxide
Sakai G., Jinkawa T., Miura N., Yamazoe N.
IEEJ Transactions on Sensors and Micromachines 118 ( 12 ) 578 - 583 1998
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Sensors and Micromachines
A search for semiconducting oxides was carried out to design a sensor selective to NO over NO2. Bi2O3was very selective to NO though not very sensitive among the various oxides examined, and NiO was proved to be the most effective promoter to Bi2O3for enhancing NO sensitivity. The sensor element using 5 wt%NiO-Bi2O3showed fairly good sensing properties to NO in the range of 0-400 ppm in sensitivity, selectivity over NO2and response rate, at 300°C. The cross-sensitivities to C3H6, C3H8, H2and O2were modest or insignificant, compared to the sensitivity to NO. Catalytic activity tests and TPD measurements indicated that the response to NO (increase in resistance) was associated with its reaction with the surface oxygen of the element, while that to NO2(decrease in resistance) resulted from its anionic adsorption. © 1998, The Institute of Electrical Engineers of Japan. All rights reserved.
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Wang X., Sakai G., Shimanoe K., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 45 ( 2 ) 141 - 146 1997.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Thin films of SiO2-WO3composites with various SiO2contents (0-20 wt%) were prepared by means of sol-gel method. The grain size of WO3decreased with increasing SiO2content, resulting in an increase in NO2sensitivity. On the other hand, the response transient to NO2was brought to be the quickest at 5% SiO2. The thin film of SiO2(5%)-WO3was far more sensitive to NO2than the thin film or sintered block of pure WO3. It could detect dilute NO2(0.1-2 ppm) in air at 350°C sensitively and fairly selectively. The NO2sensing characteristics were stable over the whole test period of 10 days. © 1997 Elsevier Science S.A.
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Spin-coated Thin Film of SiO2-WO3 Composites for Detection of Sub-ppm NO2 Reviewed
共著者：X. Wang, G. Sakai, K. Shimanoe, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 45, 141-146 45 141 - 146 1997.12
Language：English Publishing type：Research paper (scientific journal)
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Detection of Morphine in ppb Range by Using SPR (Surface-Plasmon Resonance) Immunosensor Reviewed
共著者：N. Miura, K. Ogata, G. Sakai, T. Uda N. Yamazoe
Chem. Lett., Vol. 1997, No.8, 713-714 1997 ( 8 ) 713 - 714 1997.8
Language：English Publishing type：Research paper (scientific journal)
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Sakai G., Saiki T., Uda T., Miura N., Yamazoe N.
Sensors and Actuators, B: Chemical 42 ( 2 ) 89 - 94 1997.7
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators, B: Chemical
Binding of human serum albumin (HSA) to its monoclonal and polyclonal antibody was examined by using a quartz crystal immunosensor on which the immobilized monoclonal antibody was exposed to HSA and polyclonal antibody stepwise. The association constants and rate constants of the respective steps of immunoreactions were estimated from the resonant frequency shifts at steady state and the time course of resonant frequency. The binding of HSA to the polyclonal antibody (second step) was shown to be much weaker and slower than that to the monoclonal antibody (first step), probably owing to the steric hindrance and orientation effects of the HSA already bound to the immobilized monoclonal antibody. © 1997 Elsevier Science S.A.
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Evaluation of Binding of Human Serum Albumin (HSA) to Monoclonal and Polyclonal-Antibody by means of Piezoelectric Immunosensing Technique Reviewed
共著者：G. Sakai, T. Saiki, T. Uda, N. Miura, N. Yamazoe
Sensors and Actuators B, Vol. 42, 89-94 42 89 - 94 1997.7
Language：English Publishing type：Research paper (scientific journal)
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Detection of morphine in ppb range by using SPR (surface-plasmon-resonance) immunosensor
Miura N., Ogata K., Sakai G., Uda T., Yamazoe N.
Chemistry Letters ( 8 ) 713 - 714 1997
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Chemistry Letters
Highly sensitive detection of morphine (MO) in ppb range was realized by using an immunosensor based on surface-plasmon-resonance (SPR) phenomena. The addition of MO into the antibody solution was found to reduce the incident angle shift of the SPR sensor system sharply because of the inhibition effect of MO. Based on this inhibiting principle, the present sensor could detect MO very sensitively in the concentration range of 0.1 - 10 ng/cm3(ppb).
DOI： 10.1246/cl.1997.713
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Highly sensitive detection of morphine by using immunosensor based on surface-plasmon-resonance
Sakai G., Ogata K., Uda T., Miura N., Yamazoe N.
International Conference on Solid-State Sensors and Actuators, Proceedings 1 179 - 182 1997
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：International Conference on Solid-State Sensors and Actuators, Proceedings
Highly sensitive and selective detection of morphine (MO) was realized by coupling an immunoreaction of an anti-MO monoclonal antibody and a surface-plasmon-resonance (SPR) phenomena. A normorphine-bovine serum albumin (NM-BSA) conjugate prepared as an antigen was immobilized on the Au thin film of sensor chip by physical adsorption. The incident angle of the SPR system using the NM-BSA immobilized chip increased almost linearly with increasing concentration of antibody up to ca. 5 μg/ml (ppm). The addition of MO into the antibody solution (5 ppm) was found to reduce the incident angle shift sharply because of the inhibition effect of MO. Based on this inhibiting principle, the present sensor could detect MO very sensitively in the concentration range of 0.1 - 10 ng/ml (ppb).
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水晶振動子を用いたガスおよびバイオセンサに関する研究
酒井 剛
学位論文 1996.2
Language：English Publishing type：Research paper (other academic)
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Selective and repeatable detection of human serum albumin by using piezoelectric immunosensor
Sakai G., Saiki T., Uda T., Miura N., Yamazoe N.
Sensors and Actuators: B. Chemical 24 ( 1-3 ) 134 - 137 1995.3
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators: B. Chemical
Improvements of the sensitivity and stability of a piezoelectric immunosensor for human serum albumin (HSA) have been examined. A change in resonance frequency (ΔF: sensitivity) is observed when an HSA solution is allowed to flow onto a quartz-crystal sensor immobilized with anti-HSA monoclonal antibody. ΔF is found to increase further by about three times upon subsequent exposure to a flow of the polyclonal antibody solution owing to the formation of a complex of HSA sandwiched between the two types of antibody. The final value of ΔF varies almost linearly with the HSA concentration in the range 0-20 ppm, with a sensitivity of ≈ Hz ppm-1. The resonance frequency returns reversibly to the initial level on exposure to an acidic buffer solution (pH 3.0). Furthermore, the measurement of HSA can be repeated up to about 30 times with the same sensor without a significant change in sensitivity. These results confirm that the sensor has sufficient sensitivity as well as good repeatability to be applied to a liquid flow-type HSA assay system. © 1995.
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Selective Detection of HSA (Human Serum Albumin) by Piezoelectric Immunosensor Reviewed
共著者：G. Sakai, T. Saiki, T. Uda, N. Miura, Yamazoe
Sensors and Actuators B, Vol. 24-25, 134-137 24-25 134 - 137 1995.3
Language：English Publishing type：Research paper (scientific journal)
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Miura N., Higobashi H., Sakai G., Takeyasu A., Uda T., Yamazoe N.
Sensors and Actuators: B. Chemical 13 ( 1-3 ) 188 - 191 1993.5
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators: B. Chemical
We have developed an immunosensor based on a piezoelectric quartz resonator, which detects methamphetamine (MA) in liquids from a shift of the resonant frequency. The sensor has MA-albumin conjugates immobilized on the resonator and its resonant frequency shifts downward on contact with the monoclonal antibody to MA dissolved in the phosphate buffer solution. Under the condition of a fixed concentration of the antibody, the frequency shift is attenuated by mixing MA with the antibody solution. Based on this principle, it has been possible to detect 0.02-100 ppm MA with a detection time of about 7 min. The sensor has proved to be sensitive and stable enough to detect the critical concentration (1 ppm) of MA in human urine. © 1993.
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Piezoelectric Crystal Immunosensor for Sensitive Detection of Methamphetamine (Stimulant Drug) in Human Urine Reviewed
共著者：N. Miura, H. Higobashi, G. Sakai, A. Takeyasu, T. Uda, N. Yamazoe
Sensors and Actuators B, Vol. 13-14, 188-191 13-14 188 - 191 1993.5
Language：English Publishing type：Research paper (scientific journal)
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Miura N., Minamoto H., Sakai G., Yamazoe N.
Sensors and Actuators: B. Chemical 5 ( 1-4 ) 211 - 217 1991.8
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Sensors and Actuators: B. Chemical
A new type of piezoelectric crystal sensor coated with a sputtered noble metal (Pt, Pd, Ir, or Pt-Ir) film is proposed for the detection of inflammable gases, such as H2, CO and isobutane diluted with air, in the temperature range 100-400 °C. Its sensing principle utilizes an increase in resonance frequency of the quartz crystal with the increase in temperature due to the oxidation of an inflammable gas on the coated catalyst film. Experiments show that the sensitivity increases linearly with H2concentration up to 0.4 vol.%, with a 90% response time of about 20 s to 0.3 vol.% H2at 200 °C. The sensitivity is dependent on the operation temperature due to the temperature-dependent resonance frequency of the crystal. Among the various coating films tested, sputtered Pt-Ir film gives the best sensor, with high sensitivity to inflammable gases and high resistance to interference by coexisting water vapour. © 1991.
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New Type Calorimetric Gas Sensor Using Temperature Characteristics of Piezoelectric Quartz Crystal Fitted with Noble Metal Catalyst Film Reviewed
共著者：N. Miura, H. Minamoto, G. Sakai, N. Yamazoe
Sensors and Actuators B, Vol. 5, 211-217 5 211 - 217 1991.8
Language：English Publishing type：Research paper (scientific journal)