2021/07/12 更新

写真a

イシダ ナオユキ
石田 尚之
ISHIDA Naoyuki
所属
自然科学学域 准教授
職名
准教授
外部リンク

学位

  • 博士(工学) ( 京都大学 )

研究キーワード

  • 表面間力

  • コロイド・界面化学

  • 表面ナノ構造

  • Recycling

  • Fine Particle

  • 原子間力顕微鏡

  • Surface Force

研究分野

  • ナノテク・材料 / 機能物性化学

  • ものづくり技術(機械・電気電子・化学工学) / 移動現象、単位操作

学歴

  • 京都大学    

    1997年4月 - 2000年3月

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    国名: 日本国

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経歴

  • 岡山大学   自然科学研究科   准教授

    2012年4月 - 現在

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論文

  • ニードル刺激によるfoaming誘導を利用した低真空下における真空foam乾燥の乾燥履歴の制御 査読

    日高史博, 佐藤朋, 藤岡亜希穂, 竹田昂司, 今中洋行, 石田尚之, 今村維克

    37 ( 12 )   1520 - 1527   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • アモルファス固体分散体としてメタノールから乾燥した糖類アモルファスマトリクスの物理的安定性と熱処理の影響 査読

    竹田昂司, 関藤孝成, 藤岡亜希穂, 山本佳代子, 岡本崇, 松浦傳史, 今中洋行, 石田尚之, 今村維克

    108 ( 6 )   2056 - 2062   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  • Adsorption characteristics of various proteins on a metal surface in the presence of an external electric potential 査読

    Ei Ei Htwe, Yuhi Nakama, Yuko Yamamoto, Hiroshi Tanaka, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    Colloids and Surfaces B: Biointerfaces   166   262 - 268   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Elsevier B.V.  

    The effect of the properties of a protein on its adsorption to a metal surface in the presence of external electric potential was investigated. Protein adsorption processes at different surface potentials were measured for fifteen types of proteins using an in-situ ellipsometry. The tested proteins were classified into three groups, based on the amount of protein that was adsorbed as a function of the surface potential: In First group of proteins, an increasing trend for the amount adsorbed with a more positive surface potential was found
    The amount adsorbed of α-chymotrypsinogen A and ribonuclease A (Second group) were roughly constant and independent of the applied surface electric potentials
    In Third group, the amount adsorbed decreased with increasing surface potential. This protein classification was correlated with the isoelectric points of the proteins (First group: ≤9.3
    Second group: 9.3–10
    Third group: &gt
    10). Increasing the pH positively and negatively shifted the surface potentials, allowing ß-lactoglobulin (First group) and lysozyme (Third) to become adsorbed, respectively. The surface potential range for protein adsorption was also markedly shifted depending on the metal substrate type. These findings were interpreted based on the electrostatic interactions among the protein, surface hydroxyl groups, and the applied external electric field.

    DOI: 10.1016/j.colsurfb.2018.03.035

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  • Stratification of Colloidal Particles on a Surface: Study by a Colloidal Probe Atomic Force Microscopy Combined with a Transform Theory 査読

    Ken Ichi Amano, Taira Ishihara, Kota Hashimoto, Naoyuki Ishida, Kazuhiro Fukami, Naoya Nishi, Tetsuo Sakka

    Journal of Physical Chemistry B   122 ( 16 )   4592 - 4599   2018年4月

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    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society ({ACS})  

    © 2018 American Chemical Society. Colloidal probe atomic force microscopy (CP-AFM) can be used for measuring force curves between the colloidal probe and the substrate in a colloidal suspension. In the experiment, an oscillatory force curve reflecting the layer structure of the colloidal particles on the substrate is usually obtained. However, the force curve is not equivalent to the interfacial structure of the colloidal particles. In this paper, the force curve is transformed into the number density distribution of the colloidal particles as a function of the distance from the substrate surface using our newly developed transform theory. It is found by the transform theory that the interfacial stratification is enhanced by an increase in an absolute value of the surface potential of the colloidal particle, despite a simultaneous increase in a repulsive electrostatic interaction between the substrate and the colloidal particle. To elucidate the mechanism of the stratification, an integral equation theory is employed. It is found that crowding of the colloidal particles in the bulk due to the increase in the absolute value of the surface potential of the colloidal particle leads to pushing out some colloidal particles to the wall. The combined method of CP-AFM and the transform theory (the experimental-theoretical study of the interfacial stratification) is related to colloidal crystallization, glass transition, and aggregation on a surface. Thus, the combined method is important for developments of colloidal nanotechnologies.

    DOI: 10.1021/acs.jpcb.8b01082

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  • Hydrophobic Attraction Measured between Asymmetric Hydrophobic Surfaces 査読

    Naoyuki Ishida, Kohei Matsuo, Koreyoshi Imamura, Vincent S. J. Craig

    Langmuir   34 ( 12 )   3588 - 3596   2018年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

    The interaction forces between silica surfaces modified to different degrees of hydrophobicity were measured using colloidal probe atomic force microscopy (AFM). A highly hydrophobic silica particle was prepared with octadecyltrichlorosilane (OTS), and the interaction forces were measured against silica substrates modified to produce surfaces of varying hydrophobicity. The interaction forces between the highly hydrophobic particle and a completely hydrophilic silicon wafer surface fitted well to the DLVO theory, indicating that no additional (non-DLVO) forces act between the surfaces. When the silicon wafer surface was treated to produce a contact angle of water on surface of 40°, an additional attractive force that is longer ranged than the van der Waals force was observed between the surfaces. The range and magnitude of the attractive force increase with the contact angle of water on the substrate. Beyond the effect on the contact angle, the hydrocarbon chain length and the terminal groups of hydrophobic layer on the substrate only have a minor effect on the magnitude of the force, even when the substrate is terminated with polar carboxyl groups, provided the hydrophobicity of the other surface is high.

    DOI: 10.1021/acs.langmuir.7b04246

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  • Influence of an external electric field on removal of protein fouling on a stainless steel surface by proteolytic enzymes 査読

    Ei Ei Htwe, Yuhi Nakama, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    COLLOIDS AND SURFACES B-BIOINTERFACES   159   118 - 124   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Enzymatic cleaning is a potentially useful method for removing proteinaceous fouling from solid surfaces under mild conditions. Herein, the influence of an external electric field on the enzymatic cleaning of a metal surface fouled with a protein was investigated. The model fouling protein (BSA; lysozyme) was prepared on a stainless steel (St) surface, and the resulting surface subjected to enzymatic cleaning with an electric potential being applied to the St plate. Trypsin, alpha-chymotrypsin, and thermolysin were used as model proteases. The amounts of protein remaining on the plate before and during the cleaning process were measured by means of a reflection absorption technique using Fourier transform infrared spectroscopy. In the case for BSA fouling, the cleaning efficiency of the protease tended to increase at more negative applied potentials. Whereas, there was an optimum applied potential for removing the lysozyme fouling. Atomic force microscopy analyses indicated that applying an adequate range of electric potential enhanced the enzymatic removal of protein fouling inside scratches on the St plate surface. These findings suggest the existence of two modes of electrostatic interactions for the external electric field, one with protease molecules and the other with digested fragments of the fouling protein. (C) 2017 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.colsurfb.2017.07.074

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Characteristics of proteinaceous additives in stabilizing enzymes during freeze-thawing and -drying 査読

    Takanori Shimizu, Tamayo Korehisa, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY   81 ( 4 )   687 - 697   2017年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TAYLOR & FRANCIS LTD  

    Protein-stabilizing characteristics of sixteen proteins during freeze-thawing and freeze-drying were investigated. Five enzymes, each with different instabilities against freezing and dehydration, were employed as the protein to be stabilized. Proteinaceous additives generally resulted in greater enzyme stabilization during freeze-thawing than sugars while the degree of stabilization for basic lysozyme and protamine were inferior to that of neutral and acidic proteins. Freeze-drying-induced inactivation of enzyme was also reduced by the presence of a proteinaceous additive, the extent of which was lower than that for a sugar. In both freeze thawing and freeze drying, the enzymes stabilization by the proteinaceous additive increased with increasing additive concentration. The enhancement of enzyme inactivation caused by pH change was also reduced in the presence of proteinaceous additives. The combined use of a sugar such as sucrose and dextran tended to increase the stabilizing effect of the proteinaceous additive.

    DOI: 10.1080/09168451.2016.1274637

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Surfactant-Free Solid Dispersions of Hydrophobic Drugs in an Amorphous Sugar Matrix Dried from an Organic Solvent 査読

    Koji Takeda, Yuto Gotoda, Daichi Hirota, Fumihiro Hidaka, Tomo Sato, Tsutashi Matsuura, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    MOLECULAR PHARMACEUTICS   14 ( 3 )   791 - 798   2017年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The technique for homogeneously dispersing hydrophobic drugs in a water-soluble solid matrix (solid dispersion) is a subject that has been extensively investigated in the pharmaceutical industry. Herein, a novel technique for dispersing a solid, without the need to use a surfactant, is reported. A freeze-dried amorphous sugar sample was dissolved in an organic solvent, which contained a soluble model hydrophobic component. The suspension of the sugar and the model hydrophobic component was vacuum foam dried to give a solid powder. Four types of sugars and methanol were used as representative sugars and the organic medium. Four model drugs (indomethacin, ibuprofen, gliclazide, and nifedipine) were employed. Differential scanning calorimetry analyses indicated that the sugar and model drug (100:1) did not undergo segregation during the drying process. The dissolution of the hydrophobic drugs in water from the solid dispersion was then evaluated, and the results indicated that the C-max and AUC(0-60) (min) of the hydrophobic drug in water were increased when the surfactant-free solid dispersion was used. Palatinose and/or alpha-maltose were superior to the other tested carbohydrates in increasing C-max and AUC(0-60 min), for all tested model drugs, and the model drug with a lower water solubility tended to exhibit a greater extent of over-dissolution.

    DOI: 10.1021/acs.molpharmaceut.6b01048

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Adsorption of lysozyme on base metal surfaces in the presence of an external electric potential 査読

    Ei Ei Htwe, Yuhi Nakama, Hiroshi Tanaka, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    COLLOIDS AND SURFACES B-BIOINTERFACES   147   9 - 16   2016年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The impact of external electric potential on the adsorption of a protein to base metal surfaces was examined. Hen egg white lysozyme (LSZ) and six types of base metal plates (stainless steel SUS316L (St), Ti, Ta, Zr, Cr, or Ni) were used as the protein and adsorption surface, respectively. LSZ was allowed to adsorb on the surface under different conditions (surface potential, pH, electrolyte type and concentration, surface material), which was monitored using an ellipsometer. LSZ adsorption was minimized in the potential range above a certain threshold and, in the surface potential range below the threshold, decreasing the surface potential increased the amount of protein adsorbed. The threshold potential for LSZ adsorption was shifted toward a positive value with increasing pH and was lower for Ta and Zr than for the others. A divalent anion salt (K2SO4) as an electrolyte exhibited the adsorption of LSZ in the positive potential range while a monovalent salt (KCI) did not. A comprehensive consideration of the obtained results suggests that two modes of interactions, namely the electric force by an external electric field and electrostatic interactions with ionized surface hydroxyl groups, act on the LSZ molecules and determine the extent of suppression of LSZ adsorption, All these findings appear to support the view that a base metal surface can be controlled for the affinity to a protein by manipulating the surface electric potential as has been reported on some electrode materials. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.colsurfb.2016.07.042

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Nanostructures of 3-aminopropyltriethoxysilane created on flat substrate by combining colloid lithography and vapor deposition 査読

    Naoyuki Ishida, Ryohei Nishihara, Hiroyuki Imanaka, Koreyoshi Imamura

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   495   39 - 45   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The creation of patterned structures with micro/nano-scale lengths on flat surfaces has recently been emerged as an important technique in various fields. In this report, we present a simple method to create nanopatterns of 3-aminopropyltriethoxysilane (APS) on glass substrates by the combination of colloid lithography and vapor deposition. When deposition was conducted at room temperature under natural humidity, an array of nanorings was formed on the substrate by the condensation of APS vapor on the water bridges remaining under the particles. By varying only the deposition temperature, the structure of the ordered arrays could easily be transformed: nanorings were converted to honeycomb and dot like structures by increasing temperature. This transformation proposedly occurred by the condensation and polymerization of APS vapor through the deformed particles of the colloidal monolayer. We also fabricated a patterned polymer brush array and a pore array using the obtained APS nanopattern as a template. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.colsurfa.2016.01.047

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  • Surfactant-free solid dispersion of fat-soluble flavour in an amorphous sugar matrix 査読

    Tomo Satoh, Fumihiro Hidaka, Kento Miyake, Natsuki Yoshiyama, Koji Takeda, Tsutashi Matsuura, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    FOOD CHEMISTRY   197   1136 - 1142   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    A solid dispersion technique to homogeneously disperse hydrophobic ingredients in a water-soluble solid without using surfactant was examined as follows: first, freeze-dried amorphous sugar was dissolved in an organic medium that contained a soluble model hydrophobic component. Second, the mixed solution of sugar and the model hydrophobic component was vacuum dried into a solid (solid dispersion). Methanol and six fat-soluble flavours, including cinnamaldehyde, were used as organic media and model hydrophobic components. The retention of flavours in the solid dispersion during drying and storage under vacuum was evaluated. The amorphised disaccharides dissolved in methanol up to 100 mg/mL, even temporarily (20 s to 10 days) and could be solidified without any evidence of crystallisation and segregation from flavour. The solid dispersion, prepared using a-maltose usually showed 65-95% flavour retention during drying (and storage for cinnamaldehyde), whereas >= 50% of the flavour was lost when the flavour was O/W emulsified with a surfactant and then freeze-dried with sugar. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.foodchem.2015.11.097

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  • The use of a proteinaceous "cushion" with a polystyrene-binding peptide tag to control the orientation and function of a target peptide adsorbed to a hydrophilic polystyrene surface 査読

    Hiroyuki Imanaka, Daisuke Yamadzumi, Keisuke Yanagita, Naoyuki Ishida, Kazuhiro Nakanishi, Koreyoshi Imamura

    BIOTECHNOLOGY PROGRESS   32 ( 2 )   527 - 534   2016年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    In immobilizing target biomolecules on a solid surface, it is essential (i) to orient the target moiety in a preferred direction and (ii) to avoid unwanted interactions of the target moiety including with the solid surface. The preferred orientation of the target moiety can be achieved by genetic conjugation of an affinity peptide tag specific to the immobilization surface. Herein, we report on a strategy for reducing the extent of direct interaction between the target moiety and surface in the immobilization of hexahistidine peptide (6His) and green fluorescent protein (GFP) on a hydrophilic polystyrene (PS) surface: Ribonuclease HII from Thermococcus kodakaraensis (cHII) was genetically inserted as a cushion between the PS-affinity peptide tag and target moiety. The insertion of a cushion protein resulted in a considerably stronger immobilization of target biomolecules compared to conjugation with only a PS affinity peptide tag, resulting in a substantially enhanced accessibility of the detection antibody to the target 6His peptide. The fluorescent intensity of the GFP moiety was decreased by approximately 30% as the result of fusion with cHII and the PS-affinity peptide tag but was fully retained in the immobilization on the PS surface irrespective of the increased binding force. Furthermore, the fusion of cHII did not impair the stability of the target GFP moiety. Accordingly, the use of a proteinaceous cushion appears to be promising for the immobilization of functional biomolecules on a solid surface. (c) 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:527-534, 2016

    DOI: 10.1002/btpr.2232

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  • Effect of surface hydrophobicity on short-range hydrophobic attraction between silanated silica surfaces 査読

    Yuhei Soga, Hiroyuki Imanaka, Koreyoshi Imamura, Naoyuki Ishida

    ADVANCED POWDER TECHNOLOGY   26 ( 6 )   1729 - 1733   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The interaction forces between silanated silica surfaces without nanobubbles were measured using colloidal probe atomic force microscopy (AFM). To obtain hydrophobic surfaces without nanobubbles, an aqueous solution was introduced between the surfaces following an exchange process involving several solvents. In the obtained approaching force curves, an attractive force was observed from a distance of 10-20 nm, which is an additional attractive force stronger than typical van der Waals attractions. When the surface hydrophobicity decreased, the range of this attraction decreased slightly; the attraction disappeared when the surface contact angle was below 90 degrees. In contrast, measurements in the water-ethanol mixtures revealed that the attraction persisted even when the contact angle was well below 90 degrees. The possible origin of this force was discussed on the basis of the obtained results. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan.

    DOI: 10.1016/j.apt.2015.10.017

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  • Inhibitory effects of additives and heat treatment on the crystallization of freeze-dried sugar 査読

    Kohshi Kinugawa, Mitsunori Kinuhata, Ryo Kagotani, Hiroyuki Imanaka, Naoyuki Ishida, Mizuki Kitamatsu, Kazuhiro Nakanishi, Koreyoshi Imamura

    JOURNAL OF FOOD ENGINEERING   155   37 - 44   2015年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    An amorphous matrix of a sugar is frequently used as a bulk-forming and stabilizing agent in the food industry but tends to crystallize as the result of water uptake and increase in temperature. Additives and methods used to inhibit the crystallization of amorphous sugar (sucrose) were screened in this study. Freeze-dried amorphous sucrose containing 0.5-5 wt% of additive, including salts, different types of sugars, and polymers, the crystallization temperature (T-cry) and isothermal crystallization characteristics were examined. Certain types of salts markedly increased the Tcry and prolonged the induction period for crystal nucleation. The use of 1 wt% MgCl2 was particularly effective in inhibiting sugar crystallization. The heat treatment of crystalline sucrose under appropriate conditions was also found to result in diminished sucrose crystallization. MALDI-TOF mass spectra of the heat-treated sucrose suggested that sucrose derivatives containing multiple pyranose groups were formed, which would closely relate to the crystallization inhibition. Finally, the protein stabilizing effects of the matrices were evaluated. The results indicated that both the addition of additives and the heat treatment resulted in an improvement of the protein stabilizing effect of amorphous sugar matrix, compared to that of sucrose alone. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jfoodeng.2015.01.016

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Influence of sugar surfactant structure on the encapsulation of oil droplets in an amorphous sugar matrix during freeze-drying 査読

    Shota Nakayama, Yoshifumi Kimura, Sayuri Miki, Jun Oshitani, Takashi Kobayashi, Shuji Adachi, Tsutashi Matsuura, Hiroyuki Imanaka, Naoyuki Ishida, Hiroko Tada, Kazuhiro Nakanishi, Koreyoshi Imamura

    FOOD RESEARCH INTERNATIONAL   70   143 - 149   2015年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The encapsulation of O/W emulsion droplets in a freeze-dried amorphous sugar matrix was investigated, focusing on the impact of the molecular structure of the emulsifying surfactant. O/W emulsions, containing various surfactants, were freeze-dried in the presence of a sugar. Thirty types of surfactants, including eighteen different sugar surfactants and ten types of commercially available sugar ester mixtures, were used. Linoleic acid methyl ester and trehalose were used as the oil phase and sugar. The amounts of oil droplets encapsulated in freeze-dried amorphous sugar matrix were analyzed by Fourier transform Infrared spectroscopy. Sugar surfactants were generally superior to the other classes of surfactants for oil droplet encapsulation during freeze-drying, and there was the optimum alkyl chain length of the sugar surfactant. Sugar esters generally exhibited greater oil encapsulation than sugar ethers. Larger sugar head group appeared to result in better encapsulation in the case of sugar esters, but the opposite tendency was found for sugar ethers. A limited combination of sugar surfactants (15% sucrose mono- and 85% di-stearate) resulted in the maximum oil droplet encapsulation efficiency although these surfactants are individually quite poor in the encapsulation and other tested combinations did not improve the encapsulation efficiency relative to their individual effectiveness. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.foodres.2015.02.003

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Effect of Lipid Amount on Surfactant-free Solid Lipid Nanoparticle Formation by Hot Homogenization 査読

    Jun Oshitani, Natsumi Murakami, Mikio Yoshida, Naoyuki Ishida, Koreyoshi Imamura, Hideki Ichikawa

    CHEMISTRY LETTERS   43 ( 7 )   1011 - 1013   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    The yield and size distribution of surfactant-free solid lipid nanoparticles (SF-SLNs) formed by hot homogenization were investigated by changing the amount of lipid (palmitic acid). The yield was 100% and monodispersed same-sized particles of 120-200 nm were formed at the lipid amount <= 2.8 x 10(-4) g-lipid (g-water)(-1). The yield decreased owing to phase separation, and the size increased "step-likely" to be 200 350 nm while keeping the monodispersity when the lipid amount was just above <= 2.8 x 10(-4) g-lipid (g-water)(-1). The size and the lipid amount continued to increase gradually at the lipid amount >2.8 x 10(-4) g-lipid (g-water)(-1). The results indicate that submicron-sized solid lipid particles can be formed without surfactants and that the decrease of yield and the step-like increase of particle size occur at the same lipid amount. The total surface area of the SF-SLNs was estimated using the experimental data. It is suggested that the total surface area and the lipid amount are correlated to each other.

    DOI: 10.1246/cl.140279

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    その他リンク: http://orcid.org/0000-0001-7603-1151

  • Characteristics of Sugar Surfactants in Stabilizing Proteins During Freeze-Thawing and Freeze-Drying 査読

    Koreyoshi Imamura, Katsuyuki Murai, Tamayo Korehisa, Noriyuki Shimizu, Ryo Yamahira, Tsutashi Matsuura, Hiroko Tada, Hiroyuki Imanaka, Naoyuki Ishida, Kazuhiro Nakanishi

    JOURNAL OF PHARMACEUTICAL SCIENCES   103 ( 6 )   1628 - 1637   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    Sugar surfactants with different alkyl chain lengths and sugar head groups were compared for their protein-stabilizing effect during freeze-thawing and freeze-drying. Six enzymes, different in terms of tolerance against inactivation because of freeze-thawing and freeze-drying, were used as model proteins. The enzyme activities that remained after freeze-thawing and freeze-drying in the presence of a sugar surfactant were measured for different types and concentrations of sugar surfactants. Sugar surfactants stabilized all of the tested enzymes both during freeze-thawing and freeze-drying, and a one or two order higher amount of added sugar surfactant was required for achieving protein stabilization during freeze-drying than for the cryoprotection. The comprehensive comparison showed that the C10-C12 esters of sucrose or trehalose were the most effective through the freeze-drying process: the remaining enzyme activities after freeze-thawing and freeze-drying increased at the sugar ester concentrations of 1-10 and 10-100 M, respectively, and increased to a greater extent than for the other surfactants at higher concentrations. Results also indicate that, when a decent amount of sugar was also added, the protein-stabilizing effect of a small amount of sugar ester through the freeze-drying process could be enhanced. (c) 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci

    DOI: 10.1002/jps.23988

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  • pH Effect on Properties of Surfactant-free Oil-in-water Emulsion Prepared with Oleic Acid 査読

    Yuta Akizuki, Mikio Yoshida, Naoyuki Ishida, Toshiyuki Oshiki, Jun Oshitani

    CHEMISTRY LETTERS   43 ( 5 )   604 - 606   2014年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Size distribution, zeta potential, and yield of surfactant-free oil-in-water (O/W) emulsion prepared with oleic acid were measured at various pHs after seven days from the emulsification. We found that the size distribution is almost the same regardless of pH from 9 to 3. The magnitude of zeta potential and yield remains constant at pH from 9 to 6, and decreases at pH from 6 to 3. There is a correlation between the zeta potential and the yield, but no correlation between the zeta potential and the size, suggesting that the zeta potential relates to stability of oleic acid droplets in water rather than their size.

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  • 水中の疎水化シリカ表面間に働く短距離性疎水性引力に及ぼす表面の疎水性の影響

    曽我 友平, 今中 洋行, 今村 維克, 石田 尚之

    粉体工学会誌   51 ( 5 )   343 - 348   2014年

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    記述言語:英語   出版者・発行元:一般社団法人 粉体工学会  

    The interaction forces between silanated silica surfaces with no nanobubbles were measured using colloidal probe atomic force microscopy (AFM). To obtain hydrophobic surfaces without nanobubbles, an aqueous solution was introduced between the surfaces following an exchange process involving several solvents. In the obtained approachingforce curves, an attractive force was observed from a distance of 10~20 nm, which is an additional attractive force stronger than typical van der Waals attractions. When the surface hydrophobicity decreased, the range of this attraction decreased slightly ; the attraction disappeared when the surface contact angle was below 90°。. In contrast, measurements in the water-ethanol mixtures revealed that the attraction persisted even when the contact angle was well below 90°。. The possible origin of this force was discussed on the basis of the obtained results.

    DOI: 10.4164/sptj.51.343

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  • プロピル基に表面改質した固体壁とシリカ粒子間の付着力に及ぼす改質条件の影響 査読

    吉田幹生, 日高弘喜, 石田尚之, 押谷潤, 後藤邦彰

    粉体工学会誌   51 ( 9 )   635-640 (J-STAGE)   2014年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.4164/sptj.51.635

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  • Improving the physical stability of freeze-dried amorphous sugar matrices by compression at several hundreds MPa 査読

    Ryo Kagotani, Kohshi Kinugawa, Mayo Nomura, Hiroyuki Imanaka, Naoyuki Ishida, Koreyoshi Imamura

    JOURNAL OF PHARMACEUTICAL SCIENCES   102 ( 7 )   2187 - 2197   2013年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    Amorphous matrices, composed of sugars, are markedly plasticized by moisture uptake, which results in physical instability. Our previous studies, in the compression pressure range 443 MPa, indicated that when a matrix is compressed, the amount of sorbed water at given relative humidities (RHs) decreases, whereas the glass transition temperature (Tg) remains constant. Herein, the effect of higher compression pressures than those used previously was explored to investigate the feasibility of using compression to improve the physical stability of amorphous sugar matrix against water uptake and subsequent collapse. Amorphous sugar samples were prepared by freeze-drying and then compressed at 0-665 MPa, followed by rehumidification at given RHs. The physical stability of the amorphous sugar sample was evaluated by measuring Tg and crystallization temperature (Tcry). The amounts of sorbed water, different in the interaction state, were determined using an FTIR technique. It was found that the compression at pressures of 443 MPa decreased the amount of sorbed water, which is a major factor in plasticization and crystallization, and thus markedly increased the Tg and Tcry relative to that for the uncompressed sample. Hence, the compression at several hundreds MPa appears to be feasible for improving the physical stability of amorphous sugar matrix. (c) 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2187-2197, 2013

    DOI: 10.1002/jps.23568

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  • Characteristics of amorphous matrices composed of different types of sugars in encapsulating emulsion oil droplets during freeze-drying 査読

    Koreyoshi Imamura, Yoshifumi Kimura, Shota Nakayama, Miki Sayuri, Seiji Ogawa, Tatsuya Hoshino, Jun Oshitani, Takashi Kobayashi, Shuji Adachi, Tsutashi Matsuura, Hiroyuki Imanaka, Naoyuki Ishida, Kazuhiro Nakanishi

    FOOD RESEARCH INTERNATIONAL   51 ( 1 )   201 - 207   2013年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The encapsulation of emulsion oil droplets by amorphous sugar matrices, formed by freeze-drying, was investigated, with a focus on the influence of the type of sugar. An oil-in-water emulsion, comprised of linoleic acid methyl ester (LME) and sucrose monolaurate (SML) as an oil phase and surfactant, respectively, were freeze-dried in the presence of different types of sugars. LME-droplet encapsulation during and after freeze-drying were evaluated by FTIR analysis. The loss of LME largely occurred in the early stage of freeze-drying. The size distribution of the encapsulated LME droplets remained unchanged before and after freeze-drying in most cases. The encapsulated fractions of LME droplets could be correlated with the glass transition temperature of the sugars in the fully hydrated state (T-g*), and the existence of an optimum T-g* value for the sugar matrix was predicted. The encapsulation ability of an amorphous sugar matrix was maximized when mono- and polysaccharide were combined so as to give a value for T-g* of approximately -50 degrees C, although, individually, mono- and polysaccharides were quite poor for oil droplet encapsulation. These findings suggest that the structural flexibility of the amorphous sugar matrix is a major determinant in oil droplet encapsulation by an amorphous sugar matrix during freeze-drying. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.foodres.2012.12.010

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  • Role of interfacial interactions in ordering of two-dimensional colloidal self-assemblies on polyelectrolyte multilayer surfaces 査読

    Yasuyuki Kusaka, Naoyuki Ishida, Hirobumi Ushijima

    SOFT MATTER   9 ( 11 )   3155 - 3163   2013年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    In this study, we examined the ordering of 2D colloidal particle monolayer structures formed atop polyelectrolyte multilayers (PEM) constructed by layer-by-layer deposition. We focused on the interactions between the particles and the substrate surface by changing the top layer of PEMs, along with the fabrication procedure for the PEMs. For PEMs prepared by rinsing with pure water in the fabrication process, the 2D assembly of negatively charged colloidal spheres exhibited a disordered state for positively charged PEM surfaces, whereas a well-ordered structure was formed on a negatively charged surface. Investigations with a colloid-probe atomic force microscope technique revealed that the friction force between the colloid and substrate at a zero load condition strongly affects the ordering state of the particle monolayers for relatively rigid surfaces. However, swollen PEM surfaces that were prepared by rinsing the layers with a salt solution rendered disordering of the colloidal monolayer for both positively and negatively charged surfaces and shifted to a less ordered state as the number of polyelectrolyte layers increased. For the salt-rinsed PEMs, we found that the range of the steric force of the PEMs rather than the friction force appears to be critical for the ordering of the 2D colloidal assemblies. For such swollen PEMs, we consider that the entanglement of the polymers to the colloidal particles invokes the hindrance of the particle ordering in the 2D colloidal assembly formation even though electrostatic repulsion between the colloids and the polymer layer takes place.

    DOI: 10.1039/c2sm27486h

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  • Water-in-oil Microemulsion Formation with Aqueous C-n-TAB Solution and H-AOT/Isooctane Solution 査読

    Jun Oshitani, Yuichi Baba, Shiho Takashina, Mikio Yoshida, Naoyuki Ishida

    CHEMISTRY LETTERS   41 ( 10 )   1072 - 1074   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    Aqueous C-n-TAB (n = 8, 10, and 12; octyl-, decyl-, and dodecyltrimethylammonium bromide) solution and isooctane solution of H-AOT (hydrogen bis(2-ethylhexyl) sulfosuccinate) were mixed using a vortex mixer to produce a water-in-oil (W/O) microemulsion. The microemulsion was formed with the critical amount of C-n-TAB; the order of the critical amount was C-12-TAB < C-10-TAB < C-8-TAB. A possible cause for the microemulsion formation was proposed based on the screening of the electrostatic repulsion between negatively charged AOT's polar headgroups by the positively charged C-n-TAB's polar headgroups, the hydrophobic interaction between hydrocarbon chains, and hydrated water around AOT's polar headgroup.

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  • Hydrophobic Attraction between Silanated Silica Surfaces in the Absence of Bridging Bubbles 査読

    Naoyuki Ishida, Yasuyuki Kusaka, Hirobumi Ushijima

    LANGMUIR   28 ( 39 )   13952 - 13959   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The interaction forces between silanated silica surfaces on which there were neither nanobubbles nor a gas phase were measured using colloidal probe atomic force microscopy (AFM). To obtain hydrophobic surfaces without attached nanobubbles, an aqueous solution was introduced between the surfaces after an exchange process involving several solvents. In the approaching force curves obtained, an attractive force was observed from a distance of 10-25 nm, indicating the existence of an additional attractive force stronger than the van der Waals attraction. In the retracting force curves, a strong adhesion force was observed, and the value of this force was comparable to that of the capillary bridging force. The data clearly showed that although the bridging of nanobubbles is responsible for long-range hydrophobic attraction, there also exists an additional attractive force larger than the van der Waals attraction between hydrophobic surfaces without nanobubbles. Both the ionic strength and the temperature of the solution had little influence on the force. The possible origin of the force is discussed on the basis of the obtained results.

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  • Effect of Electrolyte and Alcohol in Solution on the Hydrophobic Attraction between Alkoxylated Silica Surfaces 査読

    Naoyuki Ishida, Yasuyuki Kusaka, Hirobumi Ushijima

    CHEMISTRY LETTERS   41 ( 10 )   1273 - 1275   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    The interaction forces between silica surfaces when nanobubbles were removed from the surfaces were measured using an atomic force microscope. In the approaching force curves between the hydrophobic surfaces, an attractive force was observed from a distance of 10-20 nm. The electrolyte concentration had little effect on the range and strength of the interaction, whereas the addition of even a small amount of ethanol dramatically reduced the range of the interaction.

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  • Analysis of Adsorption and Binding Behaviors of Silver Nanoparticles onto a Pyridyl-Terminated Surface Using XPS and AFM 査読

    Nobuko Fukuda, Naoyuki Ishida, Kenichi Nomura, Tong Wang, Kaoru Tamada, Hirobumi Ushijima

    LANGMUIR   27 ( 21 )   12916 - 12922   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    In this study, we analyzed adsorption and binding behaviors of citrate-capped silver nanoparticles (AgNPs) on a pyridyl-terminated surface using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Adsorption of the AgNPs onto the pyridyl-terminated silicon wafer surface was completed through pH-controlled sol immersion. The adsorption occurred predominantly at a pH less than the pK(b) value of the pyridyl group and more than the pK(a1) of citric acid, indicating that the driving force behind adsorption was electrostatic interaction. Adsorption of citrate onto the pyridyl group also occurred at pK(al) < pH < pK(b) without AgNPs. According to XPS in the N1s region, larger deprotonation from the pyridinium-formed pyridyl groups was demonstrated subsequent to adsorption of the AgNPs. The deprotonation from the pyridinium indicates the formation of the neutral pyridyl group as the counterpart of hydrogen bonding with the carboxyl group of citrate. The binding state between the pyridyl group and citrate surrounding AgNPs is expected to be kept stable through hydrogen bonding and van der Waals force derived from the AgNPs approach to the pyridyl surface.

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  • The size of particle aggregates produced by flocculation with PNIPAM, as a function of temperature 査読

    Elizaveta Burdukova, Naoyuki Ishida, Timothy Shaddick, George V. Franks

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   354 ( 1 )   82 - 88   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    This work investigates the effect of temperature on the size of alumina aggregates formed by flocculation with temperature responsive Poly(N-Isopropylacrylamide)(PNIPAM). The results are discussed in terms of the effects of temperature on particle collision, particle adhesion and aggregate breakage. It was found that the size of alumina aggregates increases with increasing solution temperature. Particle/particle collision and aggregate breakage are largely unaffected by increasing solution temperature and therefore could not account for the change in aggregate size. The dominant factor in aggregate growth with increasing temperature was found to be the increase in the force of adhesion between alumina particles. The appearance of the adhesive force is triggered by the increase in temperature above the lower critical solution temperature of PNIPAM. (C) 2010 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jcis.2010.10.016

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  • A New Method of 'Solid Inking' and Its Application to Direct Patterning of InAs Nanowire Using Dip-Pen Nanolithography 査読

    Tong Wang, Yoshiki Shimizu, Naoyuki Ishida, Hirobumi Ushijima

    IEICE TRANSACTIONS ON ELECTRONICS   E94C ( 2 )   146 - 150   2011年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

    We report a new approach to creating a 'solid ink' and direct patterning of In As nanowires on a Si substrate using dip-pen nano-lithography (DPN). The normal method to prepare an 'ink' is a solution-based process using sonication to liquidize nanoparticles, which we call 'liquid ink' in this paper. As ink-solution-based DPN patterning has been prevalent in most studies, herein we propose a new method, 'solid inking', by which the inking process is solution-free. In our work, In As nanowires were transferred to an AFM tip by directly scanning the tip over an In As nanowire wafer at humidity over 80%. By this method, the preparation of ink and the 'inking' process is combined into one step, and a large amount of nanowires can be collected onto the tip to ensure the formation of a continuous ink flow for the direct patterning.

    DOI: 10.1587/transele.E94.C.146

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  • Surface characterization of nanoparticles carrying pH-responsive polymer hair 査読

    Syuji Fujii, Motomichi Suzaki, Yoshinobu Nakamura, Kenichi Sakai, Naoyuki Ishida, Simon Biggs

    POLYMER   51 ( 26 )   6240 - 6247   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCI LTD  

    The surface of near-monodisperse colloidal polystyrene (PS) latex particles carrying pH-responsive poly [2-(diethylamino)ethyl methacrylate] (PDEA) polymer chains as a steric stabilizer has been extensively characterized in dry and wet states. X-ray photoelectron spectroscopy and contact angle measurement studies confirm that PDEA chains are located on the PS latex particle surface. Transmission electron microscopy (TEM) studies reveal that the sterically stabilized PS particles have a core-shell morphology and wet atomic force microscopy data confirm that the pH-responsive PDEA component covers the PS latex core and the thickness of the protonated steric polymer is estimated to be approximately 15 nm. The PS latex particles can be easily dispersed in acidic aqueous media (pH 3.0) whilst they flocculate in basic aqueous media (pH 10.0) due to the pH-responsive PDEA hair. This dispersion-flocculation cycle of the PS latex is fully reversible. (C) 2010 Elsevier Ltd. All rights reserved.

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  • Effect of Grafting Density on Phase Transition Behavior for Poly(N-isopropylacryamide) Brushes in Aqueous Solutions Studied by AFM and QCM-D 査読

    Naoyuki Ishida, Simon Biggs

    MACROMOLECULES   43 ( 17 )   7269 - 7276   2010年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The effect of grafting density on the phase transition behavior of poly(N-isopropylacrylamide) (PNIPAM) grafted onto a flat substrate was investigated using an atomic force microscope (AFM) and a quartz crystal microbalance (QCM-D). We prepared PNIPAM brush layers at three different grafting densities on silicon wafers using a "grafting from" atom transfer radical polymerization (ATRP) approach. AFM imaging in water at various temperatures showed that the transition behavior of the grafted PNIPAM chains from a brush-like to a mushroom-like morphology was dependent on the grafting density: the images change abruptly from essentially featureless to domain structures across the LCST for the low-density surface, whereas the change in the images becomes less abrupt with increasing polymer graft density. The QCM-D data also indicated a significant dependence of the layer properties on the grafting density, confirming the behavior differences suggested by the A FM images. In particular, the dissipation data strongly suggest that the magnitude of lateral aggregation for the PNIPAM chains depends on the grafting density. A similar effect of grafting density was also observed for the phase transition as a function of salt concentration in sodium sulfate solutions.

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  • Temperature controlled surface hydrophobicity and interaction forces induced by poly (N-isopropylacrylamide) 査読

    Elizaveta Burdukova, Haihong Li, Naoyuki Ishida, John-Paul O'Shea, George V. Franks

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   342 ( 2 )   586 - 592   2010年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Poly (N-isopropylacrylamide) (PNIPAM) is a temperature responsive polymer. At temperature below its lower critical Solution temperature (LCST 32 degrees C) PNIPAM is soluble in water and hydrophilic. At temperature above the LCST, the polymer becomes hydrophobic and insoluble in water. At temperatures above the LCST, PNIPAM has been shown to induce flotation of previously hydrophilic minerals. The mechanism is believed to be an increase in particle hydrophobicity when PNIPAM adsorbs to the particle surfaces at high temperature. This paper investigates the interaction forces between bare silica surfaces in PNIPAM solutions. The influence of three phase contact angles on these interactions, in the presence of polymers of different molecular weights, is also examined. It was found that the presence of PNIPAM on silica Surfaces significantly increases their hydrophobicity at a temperature above the LCST. The AFM measurements Of Surface forces at high temperature also showed that strong adhesion is present between the PNIPAM coated surfaces, which is absent in the absence of polymer. These findings lead to the conclusion that the detected attractive force and subsequent adhesion result from hydrophobic attraction induced by PNIPAM at temperature above the LCST. (C) 2009 Elsevier Inc. All rights reserved.

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  • Mechanism responsible for flocculation in poly (n-isopropylacrylamide) temperature responsive dewatering-attractive interaction forces induced by surface hydrophobicity 査読

    Franks G, Burdukova E, Li H, Ishida N, O{'}Shea J.-P

    XXV International Mineral Processing Congress 2010, IMPC 2010   5   4057 - 4067   2010年

  • Characterizing the structural transition of cationic DPPC liposomes from the approach of TEM, SAXS and AFM measurements 査読

    Kenichi Sakai, Hideki Tomizawa, Koji Tsuchiya, Naoyuki Ishida, Hideki Sakai, Masahiko Abe

    COLLOIDS AND SURFACES B-BIOINTERFACES   67 ( 1 )   73 - 78   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    The structural transition of L-alpha-dipalmitoylphosphatidylcholine (DPPC) liposomes, caused by the addition of a small amount of stearylamine (SA), has been characterized. It has been reported that the shape of DPPC liposomes changes from multilamellar vesicles to large-unilamellar vesicles at the molar concentration ratio of DPPC/SA = 9.5/0.5, however, the possible diving factors for this phenomenon have not so far been presented. Flat lipid membranes consisting of DPPC and SA, prepared by the quasi-Bangham method or the Langmuir-Blodgett (LB) technique, are employed in this study when considering the molecular interaction in and between lipid membranes, which should play a key role for determining the liposome shape. The colloid probe atomic force microscopy reveals that the addition of SA results in an inter-film electrosteric repulsion. This repulsive interaction causes a significant increase in the inter-film distance, which is confirmed with freeze-fracture transmission electron microscopy (FF-TEM) and small-angle X-ray scattering (SAXS), and thereby, the large-unilamellar vesicles are formed for reducing the inter- and intra-firm repulsive forces. Taking the molecular structures into consideration, it seems that the shape transition of DPPC liposomes results from such electrostatic interactions as well as packing geometry of the two components. (C) 2008 Elsevier B.V. All rights reserved.

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  • Salt-induced structural behavior for poly(N-isopropylacryamide) grafted onto solid surface observed directly by AFM and QCM-D 査読

    Naoyuki Ishida, Simon Biggs

    MACROMOLECULES   40 ( 25 )   9045 - 9052   2007年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The salt-induced structural changes of an end-grafted poly(N-isopropylacrylamide) (PNIPAM) layer on a silica substrate were investigated in sodium sulfate solutions using an atomic force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). A PNIPAM layer was grafted onto the silicon wafer surface by free radical polymerization of NIPAM to obtain a high molecular weight polymer layer with low grafting density overall. AFM images of the coated surface were featureless at low salt concentrations commensurate with a brush-like layer. At salt concentrations >= 0.11 M, a large number of domain structures, with a characteristic size of similar to 100 nm, were seen on the surface commensurate with a collapse of the brush-like layer into mushroom-like aggregates. This critical concentration for brush collapse is in good agreement with the concentration range of between 0.1 and 0.2 M, at which the phase transition of the bulk PNIPAM is reported. Both the frequency and the dissipation data obtained using a QCM-D also showed a significant change at this concentration indicative of the layer collapse. Further analysis of these data confirmed that the observed PNIPAM structural transition was caused by a collapse of the brush-like structure as a result of dehydration of the polymer chains.

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  • Interaction forces between a poly(N-isopropylacryamide) layer grafted onto a solid surface and a hydrophobic particle 査読

    Naoyuki Ishida

    ADVANCED POWDER TECHNOLOGY   18 ( 6 )   631 - 642   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:BRILL ACADEMIC PUBLISHERS  

    The interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using atomic force microscopy. The measurements were conducted between a smooth silicon wafer on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Large repulsive forces were observed between the surfaces below the lower critical solution temperature (LCST) of PNIPAAm, while attractive forces were observed above the LCST. The magnitude of the attractive force tended to increase with the surface hydrophobicity of the particles. The temperature-induced changes in the hydration state of the grafted PNIPAAm chains are considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and hydrophobic particles in the interaction forces is discussed.

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  • Direct observation of the phase transition for a Poly(N-isopropylacryamide) layer grafted onto a solid surface by AFM and QCM-D 査読

    Naoyuki Ishida, Simon Biggs

    LANGMUIR   23 ( 22 )   11083 - 11088   2007年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    The temperature-induced structural changes of a thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) layer grafted onto a silica substrate were investigated in aqueous solution using an atomic force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). A PNIPAM layer was grafted onto the silicon wafer surface by free radical polymerization of NIPAM to obtain a high molecular weight polymer layer with low-grafting density overall. By AFM imaging, the transition of the grafted PNIPAM chains from a brush-like to a mushroom-like state was clearly visualized: The surface images of the plate were featureless at temperatures below the LCST commensurate with a brush-like layer, whereas above the LCST, a large number of domain structures with a characteristic size of similar to 100 nm were seen on the surface. Both frequency and dissipation data obtained using QCM-D showed a significant change at the LCST. Analysis of these data confirmed that the observed PNIPAM structural transition was caused by a collapse of the brush-like structure as a result of dehydration of the polymer chains.

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  • Direct measurement of hydrophobic particle-bubble interactions in aqueous solutions by atomic force microscopy: Effect of particle hydrophobicity 査読

    Naoyuki Ishida

    COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS   300 ( 3 )   293 - 299   2007年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE BV  

    Direct measurements of the interaction forces between a spherical silica particle and a small air bubble have been conducted in aqueous electrolyte solutions by using an atomic force microscope (AFM). The silica particle was hydrophobized with a silanating reagent, and the interaction forces were measured by using several particles with different surface hydrophobicities. In the measured force curves, a repulsive force was observed at large separation distances as the particle moved towards the bubble. The origin of the repulsive force was attributed to an electrostatic double-layer force because both the particle and bubble were negatively charged. After the repulsive force, an extremely long-range attractive force acted between the surfaces. These results indicate that the intervening thin water film between the particle and bubble rapidly collapsed, resulting in the particle penetrating the bubble.
    The instability of the thin water film between the surfaces suggests the existence of an additional attractive force. By comparing the repulsive forces of the obtained force curves with the DLVO theory, the rupture thickness was estimated. The hydrophobicity of the particle did not significantly change the rupture thickness, whereas the pH of the solution is considered to be a critical factor. (C) 2007 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.colsurfa.2007.02.003

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  • Interaction forces between chemically modified hydrophobic surfaces evaluated by AFM - The role of nanoscopic bubbles in the interactions 査読

    N Ishida, K Higashitani

    MINERALS ENGINEERING   19 ( 6-8 )   719 - 725   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    The interaction forces between a hydrophobic silicon plate and a silica particle in an aqueous solution were investigated with an atomic force microscope (AFM). The surfaces were hydrophobized chemically by a silane coupling agent, and the hydrophobicity (contact angle theta) of the surfaces was varied. The interactions were long-ranged at theta > 90 degrees with a discontinuous step appearing in the approaching and separating force curves respectively. The range and magnitude of the interaction were decreased with decreasing theta. On the other hand. the interactions at theta = 80 degrees was unstable and no long-range attraction was observed. When the gas phase on the surfaces was removed by flushing organic solvents between the surfaces, the interactions became short-ranged at theta > 90 degrees, and the interaction was described DLVO theory at large distances at theta = 80 degrees. A large number of nano-size domain structures were found on the surfaces by tapping-mode AFM. These results imply that the bridging of nanobubbles is the main origin of the long-range force between chemically hydrophobized surfaces and that the size of the bubble has critical effect on the range and magnitude of the attractive force. The short-range interactions without bubbles were found to consist of an electrostatic repulsive force at larger distances and an attractive force, which was sufficiently longer-ranged than the van der Waals force, at smaller distance. (C) 2005 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.mineng.2005.09.023

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  • Interaction forces measured between poly(N-isopropylacrylamide) grafted surface and hydrophobic particle 査読

    N Ishida, M Kobayashi

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   297 ( 2 )   513 - 519   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    The interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using an atomic force microscope. Measurements were conducted between smooth silicon wafers on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Below the lower critical solution temperature (LCST) of PNIPAAm, there were large repulsive forces between the surfaces, both on approach and separation of the surfaces. On the other hand, above LCST, attractive forces were observed both in approaching and in separating force curves. When surface hydrophobicity of the particles increased, the maximum attractive force tended to increase. The changes of hydration state of the grafted PNIPAAm chains depending on temperature are considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and the hydrophobic particles in the interaction forces is discussed. (c) 2005 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jcis.2005.10.068

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  • Interaction forces between thermoresponsive surface and colloidal particle in aqueous solution studied using atomic force microscopy 査読

    Ishida N, Kobayashi M

    Materials Research Society Symposium Proceedings   942   21 - 27   2006年

  • Capillary forces between planar anchoring surfaces in the isotropic phase of a nematic liquid crystal 査読

    Hiroyuki Shinto, Kiwamu Kobayashi, Terumasa Hyodo, Naoyuki Ishida, Ko Higashitani

    Chemistry Letters   34 ( 10 )   1318 - 1319   2005年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The interaction forces between the planar anchoring surfaces of a carbon microsphere and a graphite plate immersed in 8CB liquid crystal have been measured at different temperatures above the nematic-isotropic transition point, using an atomic force microscopy. The attractive force was observed between the surfaces when they came closer. The magnitude and the range of the attractive force increased with decreasing temperature. This attractive force is attributable to the confinement-induced phase separation of 8CB. Copyright © 2005 The Chemical Society of Japan.

    DOI: 10.1246/cl.2005.1318

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  • Interaction forces between hydrophobic surfaces evaluated by AFM - The role of nanoscopic bubbles in the interactions 査読

    Ishida N, Higashitani K

    Australasian Institute of Mining and Metallurgy Publication Series   481 - 486   2005年

  • 界面活性剤水溶液中での微粒子 : 気泡間相互作用力の直接測定

    石田 尚之, 四元 弘毅

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   120 ( 6 )   400 - 405   2004年7月

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    記述言語:日本語   出版者・発行元:一般社団法人 資源・素材学会  

    In many industrial processes, surfactants are used to control the dispersion and coagulation of particles in aqueous solutions. Especially, surfactants have critical effects in flotation separation. To investigate the effects of surfactants to the surface force between bubble and particle, which is critical for the particle recovery in flotation, we conducted direct measurements of the interaction forces between a spherical silica particle and an air bubble in dodecylamine hydrochloride (DAH) solution using atomic force microscope. Interaction forces were measured between the particle attached on the top of AFM probe and bubble generated on the flat surface.<BR>When a hydrophilic silica particle was used, electrostatic force was observed at large separation distance on approach of the silica and the bubble. Then long-range attractive force acted between the surfaces even when DAH concentration was low. The range of attractive force includes the penetration distance of particle into the bubble. The relation between the floatability of silica particle in batch column flotation and the interaction force was discussed.<BR>On the other hand, when the hydrophobized silica was used, the range of attractive force became short with the increase of DAH concentration. The repulsive force before attraction became very strong at high DAH concentration. The origin of the strong repulsive force is assumed to be the steric force between adsorbed dodecylammonium ions. These interaction forces cause the depression of the particle in flotation.

    DOI: 10.2473/shigentosozai.120.400

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  • 原子間力顕微鏡による水溶液中での固体微粒子 : 気泡間相互作用力の直接測定

    石田 尚之, 四元 弘毅

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   120 ( 6 )   395 - 399   2004年7月

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    記述言語:日本語   出版者・発行元:一般社団法人 資源・素材学会  

    Interaction forces between a bubble and a particle are critical for various industrial processes that handle colloidal dispersions, especially for froth flotation. Therefore, it is fundamentally important to understand the surface force between a bubble and a particle to control froth flotation process effectively. In this study, we conducted direct measurements of interaction forces between a spherical solid particle (silica and iron oxide) and a small air bubble in aqueous electrolyte using atomic force microscope (AFM). Interaction forces were measured between the particle attached on the top of AFM probe and air bubble generated on the flat surface. The forces between the silica and the bubble were repulsive over the wide range of the conditions of present experiments. The origin of the force was considered to be electrostatic force. In the case of iron oxide-air bubble system, the interaction forces were attractive when the pH was lower than isoelectric point (iep) of the ion oxide, while the forces were repulsive when the pH exceeded the iep. The attractive forces were stronger and longer-ranged than the force predicted by heterocoagulation theory. It was found that these interaction forces could explain batch column flotation results with nitrogen gas bubbles qualitatively.

    DOI: 10.2473/shigentosozai.120.395

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  • Optical observation of gas bridging between hydrophobic surfaces in water 査読

    N Ishida, M Sakamoto, M Miyahara, K Higashitani

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   253 ( 1 )   112 - 116   2002年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    The very strong and long-ranged interaction force between hydrophobic surfaces in water has been a debated issue for a long time. Recent studies suggest that the long-range attraction is attributable to the bridging of nanoscopic bubbles attached on the surfaces. However, it is still unclear at present whether such a bridging is able to exit stably or not. To clarify the existence of the gas bridge, we conducted the optical observation and the force measurement between the hydrophobic glass particle and plate in water simultaneously, using a combined apparatus of an atomic force microscope and an optical inverted microscope. It is found that (i) the image of the dark ring of ca. 1 mum in diameter appears in the region where the existence of the bridge is confirmed by force curves, but disappears when the separation between surfaces becomes shorter than the low limit of the wavelength of visible light, and (ii) the sudden disappearance of the image coincides well with the breakage of the bridge estimated from the separating force curve. The results obtained here are consistent with the above-mentioned mechanism for the long-range attraction between hydropobic surfaces in water. (C) 2002 Elsevier Science (USA).

    DOI: 10.1006/jcis.2002.8444

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  • Static method to evaluate interaction forces by AFM 査読

    N Ishida, M Sakamoto, M Miyahara, K Higashitani

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   235 ( 1 )   190 - 193   2001年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC  

    An atomic force microscope (AFM) is a very powerful tool to evaluate interaction forces between surfaces in liquids on the molecular scale, but the apparatus was not designed to measure forces in equilibrium. Hence, data obtained by AFM are not in equilibrium in principle. Here we propose a static method to obtain interaction forces between stationary surfaces in aqueous solutions using AFM. The validity of the proposed method was confirmed by comparing interaction forces measured by this method with those by the normal dynamic method for the system of a mica plate and a silica particle in electrolyte solutions where an equilibrium was nearly achieved because water molecules and ions moved much faster than surfaces, The applicability of this method to the measurement of hydrophobic attraction was then examined, and important information on the attraction was obtained. (C) 2001 Academic Press.

    DOI: 10.1006/jcis.2000.7212

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  • Nano bubbles on a hydrophobic surface in water observed by tapping-mode atomic force microscopy 査読

    N Ishida, T Inoue, M Miyahara, K Higashitani

    LANGMUIR   16 ( 16 )   6377 - 6380   2000年8月

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    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    The silicon wafer hydrophobized with OTS was immersed into water to observe the surface in-situ by tapping-mode AFM. A large number of nano-size domain images:were found on the surface. Their shapes were characterized by the height image procedure of AFM, and the differences of the properties compared to those of the bare surface were analyzed using the phase image procedure and the interaction force curves. All the results consistently implied that the domains represent the nanoscopic bubbles attached on the surface. This was confirmed by the fact that no domain was observed in the case of the surfaces hydrophobized in the AFM fluid cell without exposure to air. The apparent contact angle of the bubbles was much smaller than that expected macroscopically, which was postulated to be the reason bubbles were able to sit stably on the surface.

    DOI: 10.1021/la000219r

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  • Attraction between hydrophobic surfaces with and without gas phase 査読

    N Ishida, M Sakamoto, M Miyahara, K Higashitani

    LANGMUIR   16 ( 13 )   5681 - 5687   2000年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    To clarify the origin of the long-range attraction between hydrophobic surfaces in water, the interaction between the surfaces silanated by the popular method (type I) and that between the surfaces silanated without exposing to air (type II) were: examined using an atomic force microscope (AFM) and their characteristics were compared. The interaction between type I surfaces was long-ranged, and a discontinuous step appeared in the approaching and separating force curves, respectively, whereas the interaction between type II surfaces was short-ranged and no step was found. Once type II surfaces were exposed to air, however, the similar interaction to that for type I surfaces appeared. As for type I surfaces, the force curves depended on the local property of the surface, and the interaction in the first cycle of force measurements differed from those in the later cycles. These findings enabled us to estimate the following mechanism for the long-range attraction. When surfaces are hydrophobized, they are usually exposed to air during the hydrophobizing reaction or in the drying process. Then they are immersed in water to measure the interaction without removing microscopic bubbles on the surfaces completely. These bubbles coalesce before the surfaces contact and generate a strong long-range interaction. Hence, this interaction is not the genuine hydrophobic attraction.

    DOI: 10.1021/la991146i

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  • Effects of hydrophobizing methods of surfaces on the interaction in aqueous solutions 査読

    N Ishida, N Kinoshita, M Miyahara, K Higashitani

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   216 ( 2 )   387 - 393   1999年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ACADEMIC PRESS INC  

    The hydrophobic interaction between the surfaces hydrophobized by the adsorption of STAC in a STAC solution (system I) and the interaction between the surfaces hydrophobized by the reaction with OTS in water (system II) were investigated using an atomic force microscope, and their difference was compared. Clear differences of the interaction between systems I and II were found with respect to the force curves and the morphology of the surfactants adsorbed on the surfaces. It is postulated that the hydrophobic interaction for system II is attributable to the cavity bridging between the surfaces, but that for system I it is originated from a different mechanism. It is also implied that the existence of the surfactants in the bulk will play an important role for the hydrophobic interaction, (C) 1999 Academic Press.

    DOI: 10.1006/jcis.1999.6329

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  • 人工ダイヤモンドとグラファイトへの無機抑制剤の吸着

    石田 尚之, Mwaipopo Danford, 日下 英史, 新苗 正和, 福中 康博, 中廣 吉孝

    資源と素材 : 資源・素材学会誌 : journal of the Mining and Materials Processing Institute of Japan   113 ( 4 )   p.269 - 273   1997年4月

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    記述言語:日本語   出版者・発行元:資源・素材学会  

    DOI: 10.2473/shigentosozai.113.269

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  • 人工ダイヤモンドとグラファイトへの無機抑制剤の吸着

    石田 尚之, MWAIPOPO Danford, 日下 英史, 新苗 正和, 福中 康博, 中廣 吉孝

    資源と素材   113 ( 4 )   269 - 273   1997年

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    記述言語:日本語   出版者・発行元:一般社団法人 資源・素材学会  

    The adsorption phenomena of sodium pyrophosphate and sodium silicate were studied on synthesized diamond and unreacted graphite. Both depressants adsorbed on diamond surface, while they were rarely onto unreacted graphite. It suggests that the diamond surface adsorbed with depressant becomes hydrophilic to depress the floatation of diamond. The adsorption isotherm curves were also measured to estimate the differential heat of adsorption. They were between the typical values corresponding to physical and chemical adsorption. The dependency of adsorption density for these depressants on pH showed as follow: primary adsorption species was HP<SUB>2</SUB>O<SUB>7</SUB><SUP>3-</SUP>and adsorption isotherm equation was of Langmuir type for sodium pyrophosphate, while it was SiO (OH) <SUB>3</SUB><SUP>- </SUP>and Freundlich type for sodium silicate.

    DOI: 10.2473/shigentosozai.113.269

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  • 希土類磁石材料スクラップのリサイクリングに関する研究

    新苗 正和, 山口 潔人, 石田 尚之, DJOHARI Akskadi, 中廣 吉孝, 若松 貴英

    資源と素材   110 ( 12 )   981 - 986   1994年

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    記述言語:日本語   出版者・発行元:一般社団法人 資源・素材学会  

    The rare earth magnet has a good performance, and the production is increasing year by year. Two types of rare earth magnets are presently made as industrial products. One is a Nd-Fe-B intermetallic compound magnet and the other is a Sm-Co alloy magnet.<BR>Mixed scraps of Nd-Fe-B intermetallic compound and Sm-Co alloy are sometimes produced in the step of production. Therefore, it is desired that the recycling system of mixed rare earth magnet scraps shall be established.<BR>In the present study, the extraction and separation of Nd and Sm by solvent extraction is mainly tested to obtain the fundamental data for the hydrometallurgical treatment of the mixed rare earth magnet scraps. The results obtained in this study are summarized as follows:<BR>(1) The separation efficiency of Nd and Sm from hydrochloric acid solutions is better than that from sulphuric acid solutions.<BR>(2) The extractant combinations, EHPNA/ TOPO and EHPNA/TOA are favourable to the extraction and separation of Nd and Sm, compared with other extractants tested in this study.<BR>(3) The hydrometallurgical process of mixed rare earth magnet scraps based on oxidizing roasting, hydrochloric acid leaching, and solvent extraction is proposed.

    DOI: 10.2473/shigentosozai.110.981

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  • 新・基礎粉体工学講座(第1章)粒子の性質と測定(9)粒子間相互作用力(4)相互作用力の測定法

    石田 尚之

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   55 ( 10 )   542 - 546   2018年

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    記述言語:日本語   出版者・発行元:粉体工学会  

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  • 特別講演 原子間力顕微鏡による気液および固液界面間相互作用力の直接測定 (第137回学術講演会 : 粉体精製・環境リサイクル技術の基礎と応用) 招待

    石田 尚之

    環境資源工学   65 ( 2 )   41 - 46   2018年

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    記述言語:日本語   出版者・発行元:環境資源工学会  

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  • 第1章 粒子の性質と測定 1.9 粒子間相互作用力 1.9.3 変形・形状・表面粗さと相互作用力

    石田 尚之, 松坂 修二

    粉体工学会誌   55 ( 4 )   208 - 211   2018年

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    記述言語:日本語   出版者・発行元:一般社団法人 粉体工学会  

    DOI: 10.4164/sptj.55.208

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  • 第1章 粒子の性質と測定 1.9 粒子間相互作用力 1.9.2 液相中の相互作用

    石田 尚之, 松坂 修二

    粉体工学会誌   55 ( 2 )   104 - 112   2018年

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    記述言語:日本語   出版者・発行元:一般社団法人 粉体工学会  

    DOI: 10.4164/sptj.55.104

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  • 科学啓発活動への展開を目的とした顔料短時間合成法の開発 (特集 セラミックスと教育(3))

    米田 美佳, 石田 尚之, 寺西 貴志, 中西 真

    セラミックス   52 ( 11 )   759 - 763   2017年11月

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    記述言語:日本語   出版者・発行元:日本セラミックス協会  

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  • 新・基礎粉体工学講座(第1章)粒子の性質と測定(9)粒子間相互作用力(1)気相中の相互作用

    松坂 修二, 石田 尚之, 松山 達

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   54 ( 11 )   739 - 743   2017年

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  • 表面間力の直接測定::表面・界面のナノ構造および物性が表面間力に与える影響 招待

    石田 尚之

    色材協会誌   90 ( 9 )   333 - 338   2017年

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)   出版者・発行元:一般社団法人 色材協会  

    多くの工業分野で重要である液体中の微粒子分散系を扱ううえでは,その分散・凝集を適切に評価し,制御することが必要である。分散系の粒子の分散・凝集は粒子間に働く相互作用力(表面間力)によってほぼ支配されているため,粒子表面の性質や構造,あるいは溶媒の種類,条件などによる表面間力を正確に見積もることが,分散・凝集の適切な評価には重要である。本稿では,この表面間力の直接測定方法およびその研究動向と,そこから得られた知見について述べる。とくに,溶媒・溶質分子の表面吸着や構造の形成などといった,ナノスコピックな界面の構造・性質が表面間力を本質的にいかに変化させるかを俯瞰する。</p>

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  • 新・基礎粉体工学講座(第1章)粒子の性質と測定(9)粒子間相互作用力(1)気相中の相互作用

    松坂 修二, 石田 尚之, 松山 達

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   54 ( 11 )   739 - 743   2017年

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  • 1.9.1 気相中の相互作用

    松坂 修二, 石田 尚之, 松山 達

    粉体工学会誌   54 ( 11 )   739 - 743   2017年

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    記述言語:日本語   出版者・発行元:一般社団法人 粉体工学会  

    DOI: 10.4164/sptj.54.739

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  • 1. Particle characteristics and measurement 1.9 interparticle forces

    Naoyuki Ishida, Shuji Matsusaka

    Journal of the Society of Powder Technology, Japan   54 ( 11 )   738   2017年

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    記述言語:日本語   掲載種別:速報,短報,研究ノート等(学術雑誌)   出版者・発行元:Society of Powder Technology  

    DOI: 10.4164/sptj.54.738

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  • 疎水性引力の直接測定とその発現メカニズム (特集 界面科学部会九州地区講演会総説)

    石田 尚之

    オレオサイエンス   15 ( 6 )   253 - 259   2015年6月

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    記述言語:日本語   出版者・発行元:日本油化学会  

    DOI: 10.5650/oleoscience.15.253

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  • 液体中の粉体間に働く疎液性引力の直接測定と起源究明

    石田 尚之

    ホソカワ粉体工学振興財団年報   23 ( 0 )   38 - 43   2015年

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    記述言語:日本語   出版者・発行元:公益財団法人 ホソカワ粉体工学振興財団  

    <p>疎水性引力は,疎水性の粉体などの表面間に長距離から強い引力が働く特異な現象であり,粉体の挙動に重要な影響を及ぼす.この引力の起源についてはナノサイズの気泡の表面間架橋であるとされるが,気泡が存在しない系ではどのような力が働くか,あるいは水以外の溶媒でこの力が存在するかなど,検討されるべき点は数多く残っている.本研究では,原子間力顕微鏡を用いた直接測定により検討を行い,気泡を除去した疎水性表面間にもファンデルワールス力より強い引力が働くことを見出した.これは,疎水性引力は気泡がなくても働き得ることを示している.また,有機溶媒中の疎液化した表面間にも疎水性引力と同様の引力が観測され,水以外の溶媒中でも疎水性引力と同様の「疎液性引力」が普遍的に存在することが推察された.これらの引力の作用範囲は表面のサイズによって大きく変化し,これは発生起源の違いを反映していることが示唆された.</p>

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  • 疎水性引力の直接測定とその発現メカニズム

    石田 尚之

    オレオサイエンス   15 ( 6 )   253 - 259   2015年

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    記述言語:日本語   出版者・発行元:公益社団法人 日本油化学会  

    <p>疎水性引力は,水溶液中にある疎水性の表面間にvan der Waals引力をはるかに上回る長距離から強い引力が働く現象であり,液相コロイド分散系の挙動に重要な影響を及ぼす。しかし,なぜこのような長距離引力が働くのかというメカニズムについては,多くの研究例があるにもかかわらず長く不明であった。本稿では,原子間力顕微鏡 (AFM) による直接測定を中心とした検討により,疎水性引力の発生メカニズムの 「謎」 の解明を目的とした研究について,その成果を俯瞰したい。</p>

    DOI: 10.5650/oleoscience.15.253

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  • 柔らかい界面における相互作用の実験的測定

    石田 尚之

    粉体工学会誌   50 ( 8 )   567 - 575   2013年8月

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    記述言語:日本語   出版者・発行元:一般社団法人 粉体工学会  

    Since the interaction forces between solid surfaces in solutions are critical to understand the aggregation-dispersion behavior of colloidal particles in dispersion systems, direct measurements of the interaction forces between surfaces have been conducted in a large variety of systems over a past few decades. Recently, much effort has been paid to enable direct measurements of the interaction forces between "soft" interfaces, which show large deformation in solutions such as oil droplets, bubbles, lipid bilayers and cell surfaces, adopting atomic force microscopy techniques. This review illustrates how the interactions between surfaces including such soft interfaces can be measured and summarizes the current literature describing such experiments.

    DOI: 10.4164/sptj.50.567

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  • 第10回界面動電現象に関する国際シンポジウム(ELKIN2012)に参加して

    石田 尚之

    粉体工学会誌   50 ( 1 )   57 - 58   2013年1月

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    記述言語:日本語  

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  • 疎水性引力の直接測定とそのメカニズムの解明

    石田 尚之

    日本接着学会誌   49 ( 8 )   305 - 310   2013年

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    記述言語:日本語   出版者・発行元:一般社団法人 日本接着学会  

    DOI: 10.11618/adhesion.49.305

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  • AFMおよびQCM-Dを用いた環境応答性高分子のミクロ構造直接観察と物性評価

    石田 尚之

    オレオサイエンス   12 ( 4 )   151 - 158   2012年

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    記述言語:日本語   出版者・発行元:公益社団法人 日本油化学会  

    外部刺激に応答する高分子を固定した表面は,表面の構造や物性を環境に応じて制御できることから,各種の機能性材料へ応用が期待されるが,幅広い応用のためには固定した分子の構造変化を詳細に理解することが重要である。筆者らは,感温性高分子poly(N-isopropylacrylamide)(PNIPAM)をグラフトした表面について,原子間力顕微鏡と水晶振動子マイクロバランスを用い,温度変化による相転移に伴う構造・物性変化を,水中でその場・直接に評価する方法を確立した。また,電解質水溶液中でのPNIPAM の挙動やグラフト密度の影響等についても検討を行った。本稿では,これらの研究成果について紹介する。

    DOI: 10.5650/oleoscience.12.151

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  • The Fifth Biennial Australian Colloid and Interface Symposium に参加して

    石田 尚之

    粉体工学会誌   48 ( 7 )   495 - 497   2011年7月

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    記述言語:日本語   出版者・発行元:粉体工学会  

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  • 柔らかい界面における相互作用の実験的解析

    石田 尚之

    オレオサイエンス   11 ( 3 )   79 - 84   2011年

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    記述言語:日本語   出版者・発行元:公益社団法人 日本油化学会  

    液体中の微粒子の分散あるいは凝集といった挙動を知るためには, その支配要因である表面問の相互作用力 (表面問力) の直接測定が非常に重要であり, 固体問の相互作用については, これまで直接測定が盛んに行われてきた。近年では原子問力顕微鏡を中心とした装置により, 気泡や油滴, あるいは脂質膜や細胞のような大きな変形を伴う界面での測定が試みられるようになってきている。本稿では, このような柔らかい界面が含まれる系での表面問力の直接測定に関する最近の実験的研究を概観する。

    DOI: 10.5650/oleoscience.11.79

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  • 表面に固定した感温性高分子のナノ構造直接観察と物性評価

    石田 尚之

    C & I commun : colloid & interface communication : newsletter from DCSC   36 ( 1 )   30 - 32   2011年

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    記述言語:日本語   出版者・発行元:日本化学会コロイドおよび界面化学部会  

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  • 81st ACS Colloid & Surface Science Symposium 印象記

    石田 尚之

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   45 ( 2 )   118 - 119   2008年2月

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    記述言語:日本語  

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  • イギリス滞在記

    石田 尚之

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   44 ( 10 )   760 - 763   2007年10月

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    記述言語:日本語   出版者・発行元:粉体工学会  

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  • イギリス滞在記

    石田 尚之

    粉体工学会誌   44 ( 10 )   760 - 763   2007年

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    出版者・発行元:一般社団法人 粉体工学会  

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  • 液相中での表面間力の直接測定 : 疎水性引力を中心に

    石田 尚之

    粉体工学会誌 = Journal of the Society of Powder Technology, Japan   42 ( 5 )   342 - 346   2005年5月

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    記述言語:日本語   出版者・発行元:粉体工学会  

    DOI: 10.4164/sptj.42.342

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  • フロンティア研究シリーズ 液相中での表面間力の直接測定―疎水性引力を中心に―:疎水性引力を中心に

    石田 尚之

    粉体工学会誌   42 ( 5 )   342 - 346   2005年

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    記述言語:日本語   出版者・発行元:一般社団法人 粉体工学会  

    Direct measurement of the interaction forces between solid surfaces in liquids has become an important technique in recent years for understanding the various microscopic phenomena that affect the behavior of fine particles in many industrial processes. The history and the development of the direct measurements of surface forces are briefly reviewed. As a practical example of the force measurements, a series of the investigations for hydrophobic attraction, which is the interaction between hydrophobic surfaces in aqueous solution, using an atomic force microscope is introduced.

    DOI: 10.4164/sptj.42.342

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  • ナノ粒子の分散・凝集評価のための表面間力測定技術 (特集 粉体工業分野におけるナノテク関連評価技術)

    石田 尚之

    粉体と工業   36 ( 6 )   65 - 73   2004年6月

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    記述言語:日本語   出版者・発行元:粉体と工業社  

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  • 水溶液中における疎水性表面間力の発現機構

    石田 尚之

    粉体工学会誌   37 ( 11 )   826 - 827   2000年11月

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    記述言語:日本語  

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  • 第34回夏期シンポジウム総合討論 : 粒子表面のキャラクタリゼーション

    石田 尚之

    粉体工学会誌   36 ( 3 )   214 - 222   1999年3月

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    記述言語:日本語   出版者・発行元:粉体工学会  

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