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論文

Development of a D$$_2$$O/H$$_2$$O vapor generator for contrast-variation neutron scattering

有馬 寛*; 高田 慎一; 笠井 聡*; 大内 啓一*; 森川 利明*; 宮田 登*; 宮崎 司*; 青木 裕之; 岩瀬 裕希*; 廣井 孝介; et al.

Journal of Applied Crystallography, 56(6), p.1802 - 1812, 2023/12

The contrast-variation technique in neutron scattering experiments plays a pivotal role in distinguishing partial structures within multi-component complexes, facilitating the elucidation of distinct sample constituents. This differentiation is achieved using different isotopes, namely hydrogen and deuterium, which possess varying neutron scattering characteristics. This study presents a novel vapor generator designed for neutron scattering experiments, enabling continuous control of the D$$_2$$O/H$$_2$$O ratio of the vapor. This feature is especially useful for contrast-variation studies. The generator features two saturators and four mass flow controllers, allowing for the rapid and independent generation of D$$_2$$O/H$$_2$$O vapors. Additionally, the incorporation of the two-temperature method ensures accurate dew point control within a margin of $$pm$$0.2$$^{circ}$$Cdp. This setup proves useful for conducting time-resolved experiments and can accelerate research on functional polymers, such as polymer electrolyte membranes for fuel cells, where water potential assumes critical importance.

論文

Structural changes of polystyrene particles in subcritical and supercritical water revealed by in situ small-angle neutron scattering

柴田 基樹*; 中西 洋平*; 阿部 淳*; 有馬 寛*; 岩瀬 裕希*; 柴山 充弘*; 元川 竜平; 熊田 高之; 高田 慎一; 山本 勝宏*; et al.

Polymer Journal, 55(11), p.1165 - 1170, 2023/11

 被引用回数:0 パーセンタイル:56.45(Polymer Science)

Marine ecosystem degradation due to micro plastics is a significant environmental problem, as acknowledged by Sustainable Development Goal 14. Decomposition of plastics using near critical or supercritical water is one of the promising methods to reduce micro plastics. To attain the optimization of the method for improving environmental friendliness, it is necessary to clarify the structural change of materials during the process. We, thus, investigated the decomposition processes of polystyrene particles dispersed in deuterated water (D$$_{2}$$O) during heating under near critical or supercritical conditions by using in situ small-angle neutron scattering. Under subcritical conditions, the PS particles were swollen by D$$_{2}$$O due to increased compatibility with temperature. Near the critical point in subcritical conditions, the cleavage of PS chains in the particles occurred, so that the swollen ratio was much enhanced though the PS particles kept their shapes. In a supercritical condition, the PS particles were degraded into oil including oligomers or monomers and the phase-separated structures with styrene-rich and D$$_{2}$$O-rich regions.

論文

Direct observation of concentration fluctuations in Au-Si eutectic liquid by small-angle neutron scattering

坂口 佳史*; 高田 慎一; 川北 至信; 藤村 由希; 近藤 啓悦

Journal of Physics; Condensed Matter, 35(41), p.415403_1 - 415403_11, 2023/10

It is well-known that eutectic gold-silicon (Au-Si) alloys exhibit anomalous melting point depression, which is more than 1000 $$^{circ}$$C from the melting point of elemental Si (1414 $$^{circ}$$C). The melting point depression in eutectic alloys is generally explained in terms of a decrease of the free energy by mixing. However, it is difficult to understand the anomalous melting point depression only from the stability of the homogeneous mixing. Some researchers suggest that there are concentration fluctuations in the liquids, where the atoms are inhomogeneously mixed. In this paper, we measure the small-angle neutron scattering (SANS) of Au$$_{81.4}$$Si$$_{18.6}$$ (eutectic composition) and Au$$_{75}$$Si$$_{25}$$ (off-eutectic composition) at temperatures from room temperature to 900 $$^{circ}$$C in both solid and liquid states to observe such concentration fluctuations directly.

論文

Dynamic exchange of amphiphilic random copolymers between micelles in water; Kinetics and mechanism analyzed by TR-SANS

Hibino, Masayuki*; 高田 慎一; 廣井 孝介; 青木 裕之; 寺島 崇矢*

Macromolecules, 56(8), p.2955 - 2964, 2023/04

Amphiphilic random copolymers bearing poly(ethylene glycol) (PEG) and alkyl groups as side chains are intermolecularly self-assembled into size-controlled multichain micelles in water. The random copolymer micelles are known to induce the exchange of their polymer chains, whereas the details of the kinetics and mechanism have not been elucidated yet. Herein, we investigated the exchange kinetics and mechanism of the random copolymer chains between their micelles by time-resolved small-angle neutron scattering (TR-SANS). For this purpose, random copolymers carrying PEG and deuterated butyl or dodecyl groups were designed for deuterated micelles. After mixing deuterated and non-deuterated micelle solutions, the resulting mixtures were monitored by TR-SANS at various concentrations and temperatures. The scattering intensity of the micelle mixtures decayed with time, indicating that deuterated copolymers were gradually mixed with non-deuterated copolymers via chain exchange between their micelles to form micelles consisting of both deuterated and non-deuterated copolymers. The kinetic analysis revealed that the exchange of their polymer chains involved two mechanisms: A unimer release and insertion pathway was dominant in diluted conditions, whereas the contribution of a micelle collision pathway increased with increasing total polymer concentration and temperature. The activation energy of the polymer exchange process was dependent on the hydrophobic alkyl groups and larger than that of a related surfactant micelle.

論文

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

三浦 大輔*; 熊田 高之; 関根 由莉奈; 奥 隆之; 高田 慎一; 廣井 孝介; 岩田 高広*

J-PARC 22-02; J-PARC MLF Annual Report 2021, p.6 - 7, 2022/03

スピンコントラスト変調中性子粉末結晶構造解析法を用いてグルタミン酸結晶を測定したところ、水素核偏極度に応じて偏極中性子の回折ピーク強度がピークごとに大きく変化した。その変化を解析することにより水素原子間同士の相関関数および水素原子と他の原子との相関関数を抽出することに成功した。

論文

Star-polymer-DNA gels showing highly predictable and tunable mechanical responses

大平 征史*; 片島 拓弥*; 内藤 瑞*; 青木 大輔*; 吉川 祐介*; 岩瀬 裕希*; 高田 慎一; 宮田 完二郎*; Chung, U.-I.*; 酒井 崇匡*; et al.

Advanced Materials, 34(13), p.2108818_1 - 2108818_9, 2022/01

DNA duplexes are ideal crosslinkers for building such gels because of their excellent sequence addressability and flexible tunability in bond energy. However, the mechanical responses of most DNA gels are complicated and unpredictable. The melting curve analysis of the DNA gels reveals the good correspondence between the thermodynamic potentials of the DNA crosslinkers and the presimulated values by DNA calculators. Stress-relaxation tests and dissociation kinetics measurements show that the macroscopic relaxation time of the DNA gels is approximately equal to the lifetime of the DNA crosslinkers over 4 orders of magnitude from 0.1-2000 s. Furthermore, a series of durability tests find the DNA gels are hysteresis-less and self-healable after the applications of repeated temperature and mechanical stimuli.

論文

Spontaneous formations of nanoconfined water in ionic liquids by small-angle neutron scattering

阿部 洋*; 根本 文也*; 廣井 孝介; 大石 一城*; 高田 慎一

Journal of Molecular Liquids, 346, p.117035_1 - 117035_6, 2022/01

In this study, monodispersive nanoconfined water ("water pocket") is organized spontaneously in hydrophilic ionic liquid (IL). The IL is 1-alkyl-3-methylimidazolium nitrate ([C$$_{n}$$mim][NO$$_{3}$$] $$n$$ = 2, 6, and 8). By small-angle neutron scattering (SANS), D$$_{2}$$O aggregations in the IL are detected. There are no SANS peaks for [C$$_{2}$$mim][NO$$_{3}$$]-D$$_{2}$$O, but, in [C$$_{6}$$mim][NO$$_{3}$$]-$$x$$ mol% D$$_{2}$$O, a SANS peak can be observed at $$70 < x < 90$$ mol%. The peak intensity, position, and profile change according to water concentration and temperature. Pure [C$$_{8}$$mim][NO$$_{3}$$] has a distinct SANS peak, reflecting on the nanodomains at room temperature. Above 70 mol%, the SANS peak of [C$$_{8}$$mim][NO$$_{3}$$]-D$$_{2}$$O sharply increases and shifts to the low-Q position. The water pocket develops proportionate to water concentration, and its morphologies are visualized using an ${it ab initio}$ bead model. The alkyl chain length dependence of the water pocket is clarified by a three-dimensional reconstruction method.

論文

Structural changes in pH-responsive gelatin/hydroxypropyl methylcellulose phthalate blends aimed at drug-release systems

野上 聡*; 門田 和紀*; 内山 博雅*; 有馬 寛*; 岩瀬 裕希*; 富永 大輝*; 山田 武*; 高田 慎一; 柴山 充弘*; 戸塚 裕一*

International Journal of Biological Macromolecules, 190, p.989 - 998, 2021/11

The present study aimed to investigate the thermal-and pH-dependent gelation behavior of gelatin/HPMCP blends using ultraviolet (UV) spectrophotometry, viscoelasticity, and dynamic light scattering (DLS). We found that the release of lisinopril from gelatin/HPMCP gels can be inhibited at low pH. UV spectrophotometric analysis showed that pH had a significant effect on the transparency of aqueous HPMCP systems and gelatin/ HPMCP gels. The viscoelastic patterns of gelatin/HPMCP at pH 4.6 considerably differed from those of gelatin/ HPMCP at pH 5.2 and 6.0. DLS measurements showed that HPMCP molecules in low concentrations underwent strong aggregation below pH 4.8. Such HPMCP aggregation induces a physical barrier in the matrix structures of the gelatin/HPMCP gels, which inhibits the drug release at pH 1.2. This hydrogel delivery system using polymer blends of gelatin/HPMCP can be used in oral gel formulations with pH-responsive properties.

論文

Dynamics of water in a catalyst layer of a fuel cell by quasielastic neutron scattering

伊藤 華苗; 山田 武*; 篠原 朗大*; 高田 慎一; 川北 至信

Journal of Physical Chemistry C, 125(39), p.21645 - 21652, 2021/10

 被引用回数:2 パーセンタイル:30.86(Chemistry, Physical)

The catalyst layer (CL) in polymer electrolyte fuel cells (PEFCs) plays a critical role in the performance of a PEFC. In this study, we investigate the water dynamics in the CL using quasielastic neutron scattering (QENS) and small-angle neutron scattering. The temperature dependence of the mean square displacement $$<$$u$$^{2}$$$$>$$ shows that the freezing of water does not occur at a melting temperature in the Nafion thin film of the CL, suggesting that the water is confined in a smaller region than $$sim$$15 ${AA}$. The QENS measurements established three kinds of water in the CL: immobile water tightly connected to a sulfonic group, water in a fast mode assigned to free diffusion restricted in a sphere, and water in a slow mode described by a jump diffusion model. Assuming that these three modes were independent, the number of water molecules in each mode was estimated. On discussing the structure and dynamics elucidated in the study, we finally conclude that the coupled model of the fast and slow modes is plausible for describing the diffusion of water confined in the thin Nafion film of the CL.

論文

Relationship between viscosity and acyl tail dynamics in lipid bilayers

長尾 道弘*; Kelley, E. G.*; Faraone, A.*; 齋藤 真器名*; 依田 芳卓*; 黒葛 真行*; 高田 慎一; 瀬戸 誠*; Butler, P. D.*

Physical Review Letters, 127(7), p.078102_1 - 078102_7, 2021/08

Membrane viscosity is a fundamental property that controls molecular transport and structural rearrangements in lipid membranes. Given its importance in many cell processes, various experimental and computational methods have been developed to measure the membrane viscosity, yet the estimated values depend highly on the method and vary by orders of magnitude. Here we investigate the molecular origins of membrane viscosity by measuring the nanoscale dynamics of the lipid acyl tails using X-ray and neutron spectroscopy techniques. The results show that the membrane viscosity can be estimated from the structural relaxation times of the lipid tails.

論文

Distinguishing adsorbed and deposited ionomers in the catalyst layer of polymer electrolyte fuel cells using contrast-variation small-angle neutron scattering

原田 雅史*; 高田 慎一; 岩瀬 裕希*; 梶谷 修司*; 門浦 弘明*; 金谷 利治*

ACS Omega (Internet), 6(23), p.15257 - 15263, 2021/06

The ionomers distributed on carbon particles in the catalyst layer of polymer electrolyte fuel cells (PEFCs) govern electrical power via proton transport and oxygen permeation to active platinum. Thus, ionomer distribution is a key, to PEFC performance. This distribution is characterized by ionomer adsorption and deposition onto carbon during the catalyst-ink coating process; however, the adsorbed and deposited ionomers cannot easily be distinguished in the catalyst layer. Therefore, we identified these two types of ionomers based on the positional correlation between the ionomer and carbon Particles. From fitting with a model for a fractal aggregate of polydisperse core-shell spheres we determined the adsorbed-ionomer thickness on the carbon particle to be 51 angstrom land the deposited-ionomer amount for the total ionomer to be 50%. Our technique for ionomer differentiation can be used to optimally design PEFC catalyst layers.

論文

Modifications in the nanoparticle-protein interactions for tuning the protein adsorption and controlling the stability of complexes

Kumar, S.*; Saha, D.*; 高田 慎一; Aswal, V. K.*; 瀬戸 秀紀

Applied Physics Letters, 118(15), p.153701_1 - 153701_7, 2021/04

We report the pathways to suppress or enhance the protein adsorption on nanoparticles and thereby control the stability of the nanoparticle-protein complexes with the help of selective additives. This has been achieved by tuning the electrostatic interaction between the nanoparticles and proteins, in the presence of surfactant and multivalent counterions. The preferential binding of the proteins with the surfactant and multivalent ions induced charge reversibility of nanoparticles can lead to adsorption of an otherwise non-adsorbing protein and vice versa. The findings are demonstrated for anionic silica nanoparticles and two globular proteins [lysozyme (cationic) and bovine serum albumin (BSA) (anionic)] as model systems, in the presence of two ionic surfactants [anionic sodium dodecyl sulfate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB)], and ZrCl$$_{4}$$ as multivalent salt.

論文

Polarization analysis for small-angle neutron scattering with a $$^{3}$$He spin filter at a pulsed neutron source

奥平 琢也; 上田 祐生; 廣井 孝介; 元川 竜平; 稲村 泰弘; 高田 慎一; 奥 隆之; 鈴木 淳市*; 高橋 慎吾*; 遠藤 仁*; et al.

Journal of Applied Crystallography, 54(2), p.548 - 556, 2021/04

 被引用回数:1 パーセンタイル:34.11(Chemistry, Multidisciplinary)

$$^{3}$$Heスピンフィルタを中性子スピン解析子として使用することにより、パルス中性子源での中性子小角散乱実験において、偏極解析を行うことに成功した。本実験に使用した$$^{3}$$Heスピンフィルタは中性子小角散乱実験を行うために十分な立体角をカバーすることができ、$$^{3}$$He偏極緩和時間も数日と長く、これは実験を完遂するために十分な性能である。水素原子による非干渉性散乱は非常に大きく、試料の組成から計算によって非干渉性散乱量を見積もる試みが行われていたが、正確に非干渉性散乱量を決定することは難しかった。しかし本研究では試料内での中性子の多重散乱を考慮した偏極解析実験を行うことで、干渉性散乱と非干渉性散乱を正確に分離することが可能となった。現在までパルス中性子源での中性子小角散乱では、偏極解析の手法が確立されていなかったが、本成果によって、様々な種類の試料に対して干渉性散乱と非干渉性散乱を正確に分離することができるようになると予想される。

論文

Development of spin-contrast-variation neutron powder diffractometry for extracting the structure factor of hydrogen atoms

三浦 大輔*; 熊田 高之; 関根 由莉奈; 元川 竜平; 中川 洋; 大場 洋次郎; 大原 高志; 高田 慎一; 廣井 孝介; 森川 利明*; et al.

Journal of Applied Crystallography, 54(2), p.454 - 460, 2021/04

AA2020-0724.pdf:2.05MB

 被引用回数:1 パーセンタイル:18.34(Chemistry, Multidisciplinary)

山形大学が原子核物理実験用に開発した結晶試料の核スピン偏極技術を、スピンコントラスト偏極中性子回折測定法に展開し、水素核偏極化されたグルタミン酸を用いて粉末結晶試料中の水素の配向および凝集・分散などの構造情報を抽出できることを実証した。

論文

NACore amyloid formation in the presence of phospholipids

Pallbo, J.*; 今井 正幸*; Gentile, L.*; 高田 慎一; Olsson, U.*; Sparr, E.*

Frontiers in Physiology (Internet), 11, p.592117_1 - 592117_13, 2020/12

In this paper we investigate interactions between an aggregating peptide and phospholipid membranes, focusing on the nanometer-scale structures of the aggregates formed, as well as on the effect on the aggregation process. As a model system, we use the small amyloid-forming peptide named NACore, which is a fragment of the central region of the protein alpha-synuclein that is associated with Parkinson's disease. We find that phospholipid vesicles readily associate with the amyloid fibril network in the form of highly distorted and trapped vesicles that also may wet the surface of the fibrils.

論文

Probing the adsorption of nonionic micelles on different-sized nanoparticles by scattering techniques

Singh, H.*; Ray, D.*; Kumar, S.*; 高田 慎一; Aswal, V. K.*; 瀬戸 秀紀

Physical Review E, 102(6), p.062601_1 - 062601_11, 2020/12

The interaction of nanoparticles with surfactants is extensively used in a wide range of applications from enhancing colloidal stability to phase separation processes as well as in the synthesis of noble functional materials. The interaction is highly specific depending on the charged nature of the surfactant. In the case of nonionic surfactants, the micelles adsorb on the surface of nanoparticles. The adsorption of nonionic surfactant C12E10 as a function of surfactant concentration for two different sizes of anionic silica nanoparticles (16 and 27 nm) has been examined using dynamic light scattering (DLS) and small-angle neutron scattering (SANS). The study on different-sized nanoparticles shows that the lower curvature enhances the packing fraction whereas the loss of surface-to-volume ratio suppresses the fraction of adsorbed micelles with the increase in the nanoparticle size.

論文

Structural investigation of sulfonated polyphenylene ionomers for the design of better performing proton-conductive membranes

椎野 佳祐*; 大友 季哉; 山田 武*; 有馬 寛*; 廣井 孝介; 高田 慎一; 三宅 純平*; 宮武 健治*

ACS Applied Polymer Materials (Internet), 2(12), p.5558 - 5565, 2020/11

To achieve high-performance proton-exchange membranes (PEMs), understanding of the polymer structure/ property relationship is crucial. In particular, the structure of water clusters (number, size, interdomain distance, interconnectivity, etc.) and hydrophobic domains dominates important membrane properties, such as proton conductivity and mechanical strength, which can be adjusted by the monomer sequence in the polymer chains. In the present paper, we have prepared three sulfonated polyphenylene-based copolymers (SPP-MP, SPP-BP, and SPP-QP) whose main chain components were the same but their sequence differed by the use of different hydrophobic monomers (monophenylene, -MP; biphenylene, -BP; and quinquephenylene, -QP, respectively). Careful investigation of the proton nuclear magnetic resonance (1H NMR) spectra suggested that the randomness of the hydrophilic component (sulfophenylene unit) was dominated by the hydrophobic component: 51 % for -MP, 32 % for -BP, and 19 % for -QP, respectively. Transmission electron microscopy (TEM) observation of the three polyphenylene ionomer membranes revealed that the lower randomness of the hydrophilic component caused a larger hydrophilic domain size in their phase-separated morphology under dry conditions. Small-angle X-ray scattering (SAXS) measurements suggested that SPP-QP, with the lowest randomness of the hydrophilic component, possessed the most pronounced periodic structure under humidified conditions.

論文

Preparation, characterization, and dilute solution properties of four-branched cage-shaped poly(ethylene oxide)

野田 昂志*; 土肥 侑也*; 太田 豊*; 高田 慎一; 高野 敦志*; 松下 裕秀*

Journal of Polymer Science, 58(15), p.2098 - 2107, 2020/08

A four-branched cage-shaped poly(ethylene oxide) (4C-PEO) was prepared by a coupling reaction at very dilute condition between two kinds of end-functional four-armed star-shaped PEOs having amino and $$N$$-hydroxysuccinimide groups on their four ends, followed by purification using $$alpha$$-cyclodextrin ($$alpha$$-CD). The raw coupling reaction product shows multiple peaks including various high molecular weight multimeric products in size-exclusion chromatography measurements, while the product after $$alpha$$-CD purification shows a single peak eluted slightly earlier than the precursor star PEOs. These results suggest that the targeted 4C-PEO polymer was successfully isolated through the $$alpha$$-CD purification. Small-angle neutron scattering (SANS) measurements of the final product in dilute solution were conducted, and its chain conformation was evaluated from the scattering profile in comparison with linear and star polymers.

論文

Nanostructures and viscosities of nafion dispersions in water/ethanol from dilute to concentrated regimes

Gupit, C. I.*; Li, X.*; Maekawa, Ryosuke*; Hasegawa, Naoki*; 岩瀬 裕希*; 高田 慎一; 柴山 充弘*

Macromolecules, 53(4), p.1464 - 1473, 2020/02

The present work involved a systematic analysis of both the structural and rheological properties of Nafion dispersions carefully prepared using a standard procedure, ranging from dilute (0.1 wt %) to highly concentrated (30 wt %) conditions. Small-angle X-ray scattering confirmed the cylindrical structure of Nafion in dispersion and the unique interactions of Nafion particles acting as polyelectrolytes. Three different scaling relationships involving the zero-shear viscosities of the Nafion dispersions were determined for specific concentration regimes. However, at the upper concentration limit of approximately 30 wt %, the viscosity greatly deviated from these scaling relationships and significant shear thinning was observed. Simultaneous analyses using rheology and small-angle neutron scattering determined fully isotropic spatial correlations on a length scale of less than 60 nm, even when high shear was applied.

論文

The Effect of alkyl ammonium ionic liquids on thermal denaturation aggregation of $$beta$$-lactoglobulin

吉田 亨次*; 禪院 知寛*; Fujiyoshi, Ayako*; 真田 雄介*; 山口 敏男*; Murata, Kunihiko*; 高田 慎一; 廣井 孝介; 竹清 貴浩*; 吉村 幸浩*

Journal of Molecular Liquids, 293, p.111477_1 - 111477_9, 2019/11

Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS) measurements, and scanning and transmission electron microscope (SEM and TEM) of $$beta$$-lactoglobulin ($$beta$$-LG) are performed in alkyl (methyl, ethyl, and propyl) ammonium nitrate ionic liquids (RAN-ILs)-water mixtures at 25-100$$^{circ}$$C. The addition of these RANs decreased the thermal denaturation temperature of $$beta$$-LG, and the effect is larger with an increase of the hydrophobic part of the cation of the ILs. In ethyl ammonium nitrate (EAN) and propyl ammonium nitrate (PAN) mixtures, the fractal aggregate structure of $$beta$$-LG was found after the thermal denaturation occurred. These results are similar to those of alcohol-water mixtures. The nanoheterogeneous structure of the RAN-water mixture which consists of the hydrophobic and hydrophilic parts might affect the aggregation structure of $$beta$$-LG.

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