大川 祐輔

The unique morphology was spontaneously constructed during precipitation under acidic conditions without specific growth modifiers.

The rhabdophane-type YPO₄ particles have been synthesized in the presence of citrate ions under systematically varied reaction conditions.

The core's preferential dissolution transforms the cubic-core/monoclinic-shell manganese hexacyanoferrate particles into the hollow structure. Applying an additional growth technique, multi-shell hollow particles have also been constructed.

One-dimensional hydroxyapatite (1D-HAP) particles were synthesized via a hydrothermal process using calcium sodium nitrilotriacetate (CaNa-NTA) as a Ca2+ reservoir. CaNa-NTA dissolved slowly at 150°C to enable Ca2+ to be supplied to the aqueous phase to react with phosphate and hydroxide ions. The average length and width of the 1D-HAP particles were 6.0μm and 60 nm, respectively the former depended on the amount of CaNa-NTA loaded but the latter did not. We investigated the formation of 1D-HAP particles by powder X-ray diffraction measurement and electron microscopy observation.

Zinc oxide (ZnO) nanowires (NWs) are grown on fluorine-doped tin oxide (FTO) glass substrates via a simple reactive evaporation method without the presence of any catalysts or additives. The ZnO NWs show high crystallinity and preferential elongation along the c-axis of the hexagonal wurtzite crystal structure. The highly crystalline NWs as electron transporting layer have been used to fabricate the CH3NH3PbI3 perovskite solar cells and their photovoltaic performance were investigated. In this report, we studied the effect of filtration of PbI2-solution on surface morphology of CH3NH3PbI3 layer. Spin-coating of the filtered PbI2-solution leads to a better crystallization and relatively homogenous coverage of the CH3NH3PbI3 film, resulting in an enhancement of the solar cell efficiency compared to the cell fabricated using non-filtrated PbI2-solution. By synthesizing the CH3NH3PbI3 film using filtrated PbI2-solution, we achieved the best power conversion efficiency of 4.8% with a current density of 7.6 mA cm(-2), the open circuit voltage of 0.79V and fill factor of 0.63. (C) 2016 The Japan Society of Applied Physics

Synthesis procedures of monodisperse Prussian blue nanoparticles have been investigated to control their size in a citric acid reduction system. Two different procedures, enforced-nucleation and additional-growth ones, are applied to decrease and to increase the particle size, respectively. In the former, small amount of ascorbic acid is added in the citric acid solution as the enforced-nucleation agent, which varies the number of nuclei and thus the particle size depending on its amount. In the latter, a part of Prussian blue dispersion preliminarily prepared is introduced into the reactant solution that provides additional reaction resources for the further growth. As a result, Prussian blue nanoparticles are prepared in the range of 20-100nm in the mean size with narrow size distribution.

A reagentless electrochemical biosensor for hydrogen peroxide was fabricated. The sensor carries a monolayer of nanocomplex composed of horseradish peroxidase and Au-nanoparticle, and responds to hydrogen peroxide through the highly efficient direct electron transfer at a mild electrode potential without any soluble mediator. Formation of the nanocomplex was studied with visible spectroscopy and size exclusion chromatography. The sensor performance was analyzed based on a hydrodynamic electrochemical technique and enzyme kinetics. The sensor was applied to fabrication of sensors for glucose and uric acid through further modification of the nanocomplex-carrying electrode with the corresponding hydrogen peroxide-generating oxidases, glucose oxidase and urate oxidase, respectively.

One-dimensional yttrium hydroxide particles of hexagonal crystal structure were selectively synthesized through a hydrothermal reaction of yttrium chloride solution that was alkalized by two-step addition of sodium hydroxide solution. Keeping the YCl3 solution at pH similar to 6.8 for a few minutes before raising the pH to the sufficient level (pH similar to 13) was concluded to be the practical requirement for the one-dimensional Y(OH)(3) particle formation. This requirement was successfully achieved by the two-step addition procedure that was applicable to adjust the pH values independently. The size distribution of one-dimensional particles was changed depending on the interval time between alkali-additions and on the pH of the hydrothermal reaction. The formation mechanism of the one-dimensional particles was also discussed.

A procedure to obtain monodisperse nanoparticles of cobalt(1) hexacyanoferrate(III) was investigated. To prevent a reaction with [Fe(CN)(6)](3-), Co2+ was stored in the form of a citrate complex at pH 7.8. By lowering the pH to 3.4 by the addition of acid, part of the Co2+ was released and reacted with [Fe(CN)(6)](3-) to form nuclei, followed by their growth via mass-transfer of Co2+ from the citrate complex to the solid. Here, gelatin was employed as a protective colloid. The particles obtained were cubic and fairly monodisperse. The mean particle size was typically 160 nm and varied from 30 to 450 nm, depending on the reactant contents. The formation mechanism associated with equilibrium shifts was supported by a calculated estimation of free Co2+ on the basis of the equilibrium relationships involved in the preparation system.

ソバは酸化防止効果などの生理作用をもつルチンを多く含むことから, 健康食品としての期待が高い。本研究ではソバ食品加工時におけるソバルチンと小麦グルテンの相互作用がソバ蒸しパンに及ぼす影響を解明し, その結果から物理的特性が良好で機能性の高いソバ食品の膨化調理条件を考察した。普通およびダッタンソバ粉に活性グルテンを0〜10wt%混合したバッターを調製し, これを15分間蒸した各種ソバ蒸しパンの物性を測定した。蒸しパンのテクスチャー特性のうち, かたさの項目でダッタンソバ試料の値が高くなり, 凝集性では値が低くなった。また, 蒸しパンの応力-ひずみ曲線の微分解析よりダッタンソバ試料は噛み込んだ時に硬く脆い食感となる傾向を示した。さらに体積の測定を行い, すだちを観察した結果, ダッタンソバ試料は膨化体積が小さく, すだちは不均一できめが粗かった。またソバの機能性の1つとして抗酸化能についても比較し, グルテン添加により各種ソバ蒸しパンの抗酸化能が向上することが明らかとなった。

ゼリー状ソバ食品の調理条件の解明を目指した基礎実験として,ソバに含有するルチンの添加量を変えて調製したルチン-ゼラチン混合系ゲルのゲル特性を追跡した。細線加熱法および動的粘弾性の各測定では,ルチン添加によるゼラチンのゾル・ゲル転移温度の変動はみられなかった。しかし,結晶が析出し始める1,000ppm以上のルチン添加では,無添加試料に比較してゲル化後の貯蔵弾性率が著しく上昇したことから,この添加量以上では,ゲル化後のゼラチン分子の架橋形成が促進されることが示唆された。この濃度以上では,ルチン結晶の析出量が増加するとともに,有意にゲルの破断応力は上昇して硬さを増し,破断歪率は低下して脆くなった。以上のことから,ゲル中におけるルチン結晶の析出は,ゲルの物性に影響を与えると考えられる。そのため,口当りの好ましいゼリー状ソバ食品の調理加工には,ルチン含量の低い普通ソバ粉や,ソバ茶抽出液などの利用が望ましいといえる。

A novel electrochemical biosensor for hydrogen peroxide with high electron transfer efficiency was developed using a nanocomplex composed of horseradish peroxidase and Au-nanoparticle. The nanocomplex was prepared through adsorption of horseradish peroxidase on an Au-nanoparticle. The nanocomplexes were easily coagulated and immobilized on an ITO electrode as a monolayer film by simply casting the nanocomplex dispersion and drying below 10 degrees C. The electrode worked as a hydrogen peroxide biosensor featuring high electron transfer efficiency without any soluble mediator at a mild electrode potential of +0.15V vs. Ag/AgCl.

Monodisperse particles of tungsten(VI) oxide monohydrate were prepared in a hydrothermal system at 40 degrees C, where 20 ml of HCl solution (1.50 mol/l) was added to the same volume of Na2WO4 aqueous solution (0.50 mol/l) with magnetic stirring, followed by standing in an air oven for 168 h. The shape of the particles was square platelet and the mean size was 0.72 mu m with 10% of the coefficient of variation. The XRD pattern was in good agreement with the standard JCPDS data for WO3 center dot H2O. The effects of counter cation and anion of the starting materials in addition to the preparation temperature and acid concentration were also examined. (c) 2006 Elsevier B.V. All rights reserved.

魚の煮汁を冷やして得られた"煮こごり"は,日本の伝統的な料理である.本研究では魚の代わりに鶏手羽先を材料として加熱温度及び加熱時間を変化させた煮汁から得た"煮こごり"ゲルを調製し,ゲル化及び溶解過程における動的弾性率の変化並びにゲルの破断応力を測定し,物性の変化を追跡した.さらに,SDS-PAGE,サイズ排除クロマトグラフィーにより溶出たんぱく質の分子量分布並びに抽出コラーゲン量の変化を微視的に追跡した.鶏手羽先から得た"煮こごり"は高温長時間加熱により硬いゲルを形成し,煮こごりゾル中に含まれるたんぱく質は熱加水分解により,加熱時間の経過に伴い低分子化していることが明らかとなった.

Supersaturation ratio, S, has been theoretically related to the supply rate of solute, Q, from growth rate and mass-balance equations in the quasi-steady state in the growth process of isotropic monodisperse particles. The derived equation, (S - 1) = (1/D + 1/kr)(Q/beta C(0)nr) + 2V(m)gamma/rRT, suggests a linear dependence of S on Q under constant n and r, where D is the diffusion coefficient, k is the rate constant for surface-reaction, C-0 is the solubility, n and r are the number and radius of growing particles, respectively, V-m is the molar volume of particles, R is the gas constant, T is the absolute temperature, and beta is the shape factor defined by beta equivalent to (1/r(2)) dv/dr, where v is the volume of an individual particle. The equation was applied to the analysis of growth kinetics and determinations of critical supersaturation ratio in monodisperse AgBr particles in the controlled double-jet system with the assistance of a potentiometric supersaturation measurement. In both cubic and octahedral particles, growth rates were completely limited by diffusion and surface-reaction at pBr (equivalent to -log[Br-]) 3.0 and 1.0, respectively, while the growths were intermediate of them at pBr 2.0 and 4.0. The growth parameters, DC0 and kC(0), were experimentally determined. Also, critical supersaturation ratio was estimated as 1.28 as an average in the present study.

煮こごりを始めとするゼラテン料理に加えられるアルコール量のゲル化に及ぼす影響をみるために低濃度から高濃度(1%,3%,5%,10%,20%)まで変化させたアルコール添加ゲルを調製し,動粘度モニタリングシステム,旋光度,動的粘弾性,レオメーターによる力学特性及び^<17>O-NMRのスピン-格子緩和時間(T_1)の測定,電子顕微鏡によるゲル内部の組織観察を行い,得られた結果を以下にまとめた。(1)アルコール添加濃度が高濃度になるほどゼラチン分子のゲル化特性(ゲル化温度,旋光度,粘性率及び弾性率の低下)に影響を及ぼし,初期の架橋形成も遅れることが示唆された。つまり,高直度のアルコール添加はゲル化が阻害されることが明らかとなった。(2)10%以上の高濃度アルコール添加ゲルの物性は,表面はゴム状の延性的性状を有したが,(1)の結果から内部は網目構造の少ない口どけの早いゲルを形成すると推測された。(3)ゾルのNMR測定及びゲル内部の組織観察から,10%以上の高濃度アルコール添加はアルコールと溶媒の水との相互作用により,ゼラチン分子の網目形成が阻害され,ネットワークの少なく組織構造の変化したゲルを形成することが認められた。

ゼラチン溶液に各種糖を添加した場合のゲル化機構を明らかにするために動粘度モニタリングシステム, 旋光度, 動的粘弾性, レオメーターによる力学的特性及び¹⁷O-NMRのスピン-格子緩和時間 (T₁) の測定を行い, 得られた知見を以下にまとめた.<BR>1) 各種糖添加により, 対照と比べてゲル化が早く始まり, 高温側でゲル化し, ゲル化完了までに長時間を要した.<BR>2) ゲル化は, まず粘性率が増加する現象に始まり, 続いて弾性率の増加, 最後に旋光度という順で変化が起きていた.<BR>3) 各種糖添加試料はいずれも対照と比べて硬いゲルを形成したが, 糖の種類によりゲル強度に差がみられた.<BR>4) ゼラチンゲルの状態と共存する糖の種類との関係について, ¹⁷O-NMRのスピン-格子緩和時間 (T₁) の測定を行ったところ, 糖の赤道結合 (e-OH) の数に関係があることが示唆された.

ゼラチン溶液に糖及びアルコールを添加した場合のゲル化機構を動粘度モニタリングシステム,旋光度,動的粘弾性,レオメータの測定により検討した結果を以下にまとめた。1)糖及びアルコールの添加はアルカリ処理低温抽出ゼラチンのゾル-ゲル変換に影響を及ぼした。糖添加によりゲル化開始時間は短く,ゲル化が完了した時間は長く,ゲル化温度は高くなった。一方,エタノール20%添加ではゲル化開始時間,ゲル化時間は長く,ゲル化温度を低下させた。2)本試料ゼラチンのゲル化では,粘性率の増加から始まり,続いて弾性率の増加が起こり,最後に旋光度という順で変化が起きていた。3)ソルビトール添加はゼラチン分子のへリックス形成に有効であり,弾性率も上昇し,硬いゲルを形成したが,高濃度のエタノール添加はゼラチンのヘリックス形成に抑制的に働き,弾性率も低下し、破断波形において延性を増した。