森田 剛

A high-temperature high-pressure cell equipped with a metallic window was developed for small-angle neutron scattering (SANS). The feasibility of a Ti alloy (Ti–6Al–4V) as a candidate window material was assessed, considering its mechanical strength and neutron characteristics. SANS experiments should be conducted using safe and reliable materials without risk of window damage or leakage of the activated samples due to window breakage. SANS profiles measured for supercritical heavy water showed maximum scattering intensity at temperatures and pressures near the critical density. Additionally, the utility of the cell for observations of the decomposition of plastic in supercritical water is presented. The cell facilitates analysis of reaction mechanisms under sub- and supercritical conditions, which could provide detailed information to aid efficient decomposition and recycling, contributing to a sustainable society.

The study revealed element-ratio dependence of the 5d-states and mechanism of the 5d-state changes in solid-solution-type Au–Pt alloy nanoparticles.

Abstract Alcohols and urea are widely used as effective protein denaturants. Among monohydric alcohols, 2,2,2‐trifluoroethanol (TFE) has large cosolvent effects as a helix stabilizer in proteins. In contrast, urea efficiently denatures ordered native structures, including helices, into coils. These opposing cosolvent effects of TFE and urea are well known, even though both preferentially bind to proteins; however, the underlying molecular mechanism remains controversial. Cosolvent‐dependent relative stability between native and denatured states is rigorously related to the difference in preferential binding parameters (PBPs) between these states. In this study, GCN4‐p1 with two‐stranded coiled coil helices was employed as a model protein, and molecular dynamics simulations for the helix dimer and isolated coil were conducted in aqueous solutions with 2 M TFE and urea. As 2 M cosolvent aqueous solutions did not exhibit clustering of cosolvent molecules, we were able to directly investigate the molecular origin of the excess PBP without considering the enhancement effect of PBPs arising from the concentration fluctuations. The calculated excess PBPs of TFE for the helices and those of urea for the coils were consistent with experimentally observed stabilization of helix by TFE and that of coil by urea. The former was caused by electrostatic interactions between TFE and side chains of the helices, while the latter was attributed to both electrostatic and dispersion interactions between urea and the main chains. Unexpectedly, reverse‐micelle‐like orientations of TFE molecules strengthened the electrostatic interactions between TFE and the side chains, resulting in strengthening of TFE solvation.

Abstract Density fluctuation is a vital concept for understanding disordered systems. A supercritical fluid is a typical disordered system having extremely large inhomogeneity. To determine the density fluctuations using a scattering method, the key physical quantities are the fluid density and the normalized scattering intensity, as well as the small-angle scattering signals. Here, we propose a methodology to obtain all of these quantities absolutely from a scattering experiment. Normalization of scattering intensity relating to the number of molecules per unit volume was performed using fluid density evaluated directly from in situ measurements of the X-ray absorption coefficients. Conversion of scattering intensity to absolute value concerning scattering volume was achieved utilizing the value of the density fluctuation in the ideal state. An analysis of supercritical carbon dioxide confirmed the validity of the present method. By applying this method, the density fluctuations of supercritical methanol were quantitatively determined for the first time.

A mixture of poly(benzyl methacrylate) (PBnMA) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mim][NTf2]) exhibits lower-critical-solution-temperature (LCST)-type phase separation. An investigation combining magic-angle spinning NMR spectroscopy and small-angle scattering was performed to gain new...

The effects of pH changes and saccharin (SAC) addition on the nanostructure and mobility of the cationic aminoalkyl methacrylate copolymer Eudragit E PO (EUD-E) and its drug solubilization ability were investigated. Small-angle X-ray scattering performed using synchrotron radiation and atomic force microscopy showed that the EUD-E nanostructure, which has a size of approximately several nanometers, changed from a random coil structure at low pH (pH 4.0-5.0) to a partially folded structure at high pH (pH 5.5-6.5). The EUD-E also formed a partially folded structure in a wide pH range of 4.5-6.5 when SAC was present, and the coil-to-globule transition was moderate with pH increase, compared with that when SAC was absent. The equilibrium solubility of the neutral drug naringenin (NAR) was enhanced in the EUD-E solution and further increased as the pH increased. The enlargement of the hydrophobic region of EUD-E in association with the coil-to-globule transition led to efficient solubilization of NAR. The interaction with SAC enhanced the mobility of the EUD-E chains in the hydrophobic region of EUD-E, resulting in changes in the drug-solubilizing ability. 1H high-resolution magic-angle spinning NMR measurements revealed that the solubilized NAR in the partially folded structure of EUD-E showed higher molecular mobility in the presence of SAC than in the absence of SAC. This study highlighted that solution pH and the presence of SAC significantly changed the drug solubilization ability of EUD-E, followed by changes in the EUD-E nanostructure, including its hydrophobic region.

Previously, we reported the formation of 100-200 nm disk- and tube-like nanoparticles by hydration of L-ascorbyl 2,6-dipalmitate (ASC-DP) and distearoylphosphatidylethanolamine polyethylene glycol 2000 (DSPE-PEG) films prepared at an initial molar ratio of 2:1. This study investigated the feasibility of nanoparticle formation with higher ASC-DP loading. Although particle size distribution determined by dynamic light scattering showed a multimodal pattern including micro-sized particles at a molar ratio of 3:1, the mean particle size gradually decreased with a further increased molar ratio. Homogeneous ca. 240 nm nanoparticles with a unimodal size distribution were obtained at a molar ratio of 10:1. FE-TEM showed that the nanoparticles at a molar ratio of 10:1 were rod-shaped with a diameter of ca. 100 nm and a length of ca. 300 nm. After centrifugation, X-ray analysis of the nanoparticle precipitates showed that these rod-like nanoparticles were composed of a series of lamellar structures with 3.7 nm repeated units. The molar ratio of ASC-DP/DSPE-PEG in the nanoparticle precipitates determined by 1H NMR measurements was 68.8:1. The rod-like nanoparticles should be composed of a core-shell structure, where a small amount of DSPE-PEG covers the lamellar structure of ASC-DP. Further increase in the ASC-DP/DSPE-PEG molar ratio over 33:1 no longer provided nanoparticles. Hence, to prepare a stable ASC-DP nanoparticle suspension, it is necessary to prepare ASC-DP/DSPE-PEG films containing at least 3 mol% DSPE-PEG.

<p>Solvent fluctuation (<italic>G</italic>_TFE-TFE) of 2,2,2-trifluoroethanol (TFE)–H₂O mixture was determined by small-angle X-ray scattering investigation. Protein’s coil–helix transition can be induced by preferential binding of TFE (Δ<italic>Γ</italic>₂₃) without aggregation of TFE.</p>

Polymeric micelles are invaluable media as drug nanocarriers. Although knowledge of an interaction between the micelles is a key to understanding the mechanisms and developing the superior functions, the interaction potential surface between drug-incorporated polymeric micelles has not yet been quantitatively evaluated due to the extremely complex structure. Here, the interaction potential surface between drug-entrapped polymeric micelles was unveiled by combining a small-angle scattering experiment and a model-potential-free liquid-state theory. Triblock copolymer composed of poly(ethylene oxide) and poly(propylene oxide) was investigated over a wide concentration range (0.5-10.0 wt %). Effects of the entrapment of a water-insoluble hydrophobic drug, cyclosporin A, on the interaction were explored by comparing the interactions with and without the drug. The results directly clarified the high drug carrier efficiency in terms of the interaction between the micelles. In addition, an investigation based on density functional theory provided a deeper insight into the monomer contribution to the extremely stable dispersion of the nanocarrier.

© 2019 American Chemical Society. Fusion growth from each nanocluster applying the random coil-globule transition of a thermoresponsive polymer was explored for alloy nanoparticle (NP) formation for the first time. The fusion growth of bimetallic Au-Pt alloy NPs was examined at 100, 150, and 200 °C via the structural collapse caused by the transition of a thermoresponsive polymer, poly(N-isopropylacrylamide). A significant temperature dependence was revealed in the formation path, even in the narrow range of reaction temperatures studied here. Structural investigations for the products were performed using transmission electron microscopy, energy-dispersive X-ray spectrometry, elemental mapping, X-ray absorption fine structure, and X-ray diffraction. At 100 °C, Au NPs slightly alloyed with Pt atoms rather than form neat Au NPs. The element ratio was determined to be Au:Pt = 12:1 or less of Pt atoms. Small Pt particles coated the surface of the central NPs. A nonmetallic component of Pt atoms was mainly detected in the product solution on the basis of the number of unoccupied Pt 5d orbitals. Aggregates comprising small particles several nanometers in size and void parts were generated at 150 °C. All of the characterization results indicate that the hydrothermal condition at 200 °C led to the production of Au-Pt alloy NPs having a solid-solution-type structure. The reaction path of the fusion growth of the bimetallic NPs is discussed on the basis of the effect of the temperature applied during the reaction.

© 2019 the Owner Societies. A novel Raman scattering enhancement was discovered using colloid nanoparticles conjugated with an amine-based copolymer. The interaction potential surface between Raman scattering enhancing nanoparticles was clarified by combining a small-angle scattering method and a model-potential-free liquid-state theory as an in situ observation in the solution state. The potential surface indicates that the most stable position is located around 0.9 nm from the particle surface, suggesting the existence of a nanogap structure between the nanocomposites. The change in Raman scattering enhancement was also acquired during the dispersion process of the aggregated nanocomposites through a glutathione-triggered nanosensing reaction.

© 2019 CSIRO. Aqueous solutions of ionic liquids have unique mixing states. Fluctuations are useful for understanding the inhomogeneity of the mixing states. In this study, an aqueous solution of tetrabutylphosphonium trifluoroacetate, ([P4,4,4,4]CF3COO), which exhibits a lower-critical-solution-temperature-type phase transition, was investigated. Focussing on the concentration and temperature range near the critical point, the fluctuations were evaluated by combining three kinds of experimentally obtained data: Small-angle X-ray scattering intensity, partial molar volumes, and isothermal compressibility. Using Kirkwood-Buff integrals, individual density fluctuations of water and [P4,4,4,4]CF3COO were calculated, and these suggested that a large number of water molecules hydrated [P4,4,4,4]CF3COO ion pairs, and the hydrated ion pairs aggregated near the critical point. The relationship between the mesoscopic fluctuations and the macroscopic phase transition was clarified by drawing counter maps of the fluctuations in the phase diagrams.

© 2018 Liquid water has an inhomogeneous structure in the molecular organization, due to the cooperative hydrogen bonding. Here, we report the effect of ionic liquid cations on the structural fluctuations of water using the small-angle X-ray scattering method. Aqueous solutions of imidazolium-, ammonium-, and phosphonium-based cations with butyl alkyl-chain(s) were investigated as typical cations forming ionic liquids. The investigation was performed on the basis of the concept of Mixing Scheme I, within which water maintains percolation of the hydrogen-bonding network and therefore holds the characteristic property of water even in solution systems. Dissolution of typical ionic liquid cations led to extreme reduction in the mesoscopic structural fluctuations, compared to molecular liquid. This reduction of the fluctuation is discussed both in terms of the contribution of the hydrophobic hydration of water molecules around the cations and the distorted hydrogen bonding network in bulk water due to the hydrophilic effect.

© 2018 American Chemical Society. The Hansen solubility parameters (HSPs) of asphaltene model compounds were determined experimentally via solubility testing. For the test, we synthesized various archipelago- and continental-type molecule model compounds: 5 were steroid-derived naphthoquinoline compounds; 14 were phenanthrene/pyrene-derived compounds; 2 were nickel porphyrins; and 1 was an alkyl hexabenzocoronene molecule. Some of them contain nitrogen as the quinoline or porphyrin structure, oxygen as the furan structure, and sulfur as the thiophene structure. Using the Hansen sphere method, the HSPs δd, δp, and δh were successfully determined with only small errors, with values of 18.7-21.0, 2.7-8.1, and 2.2-6.5 MPa1/2, respectively. For real asphaltenes, these values were about 19, 4, and 4 MPa1/2, respectively. The solubility characteristics of the model compounds were found to be complex, because there is not clear relationships between solubility and chemical structures. Even slight structural differences, such as the type and location of heteroatoms, greatly changed the Hansen sphere radius, R0. The HSP analyses will enable the development of a mixing strategy for model compounds, to mimic asphaltene.

© 2017 Elsevier B.V. We characterized the effects of tetrapropylammonium and tetrabutylammonium cations, typical constituent cations of ionic liquids, on the molecular organization of liquid water by using the 1-propanol probing methodology developed by us earlier. Of late, much attention has been paid to the properties of aqueous solutions of ionic liquids. Our results indicated that both ions gained hydrophobicity considerably. There is a remarkable difference in hydrophobicity between tetramethyl- and tetraethyl-ammonium cations we studied earlier using the same methodology. The hydrophobicity of tetrabutylammonium cation was twice stronger than that of tetrapropylammonium. We point out that the present methodology describes strictly at the equilibrium situation. Nevertheless, the resulting hydration numbers of these cations are close to the conclusions given by spectroscopic studies, which provides information of transient situation.

© 2017 Elsevier B.V. To study the structural fluctuation of supercritical solutions, we introduced three fluctuational parameters, a scattering factor, a density factor and a volume factor, which were based on the Bhatia–Thornton theory. In the present study, the density dependence of the structural inhomogeneity in a supercritical aqueous solution of n-pentane was discussed using the scattering factor and the density factor obtained from small-angle X-ray scattering and the fluid density measurements, respectively. Although both these factors have their maxima at the same density position in the case of neat supercritical fluids, a significant difference between the two factors is observed in the binary solution. The large difference occurs by the contribution of the concentration fluctuation in the system. Based on the difference between the factors, it is suggested that a phase separation of the system exists in the higher-fluid-density region.

© 2017 Elsevier B.V. Raman spectral changes of CO2 induced by the absorption were evaluated for the Fermi dyad continuously up to 15 MPa of equilibrium CO2 pressure. Little pressure dependence was observed for both the band positions and the bandwidth of the absorbed CO2, compared to those for neat supercritical CO2. Furthermore, the band positions lay at much lower values than those for neat CO2. The bandwidth broadening was observed for the absorbed CO2 even in the lower pressure region. The absorption state of CO2 is discussed from the viewpoints of structural fluctuations and interaction forces induced by the surrounding ionic liquid.

© the Owner Societies 2017. We have studied the mixing scheme of an aqueous solution of ionic liquid tetrabutylphosphonium trifluoroacetate, [P4,4,4,4]CF3COO, in the water-rich region. The mixture shows phase separation with a lower critical solution temperature. To learn how the solute [P4,4,4,4]CF3COO species interact with each other in the dilute region, the third derivative quantities of Gibbs energy in terms of enthalpy, HEIL-IL, and volume, VEIL-IL, are evaluated. In the present study using up to the third derivative quantities, we conclude that [P4,4,4,4]CF3COO turns out to be an extremely strong hydrophobe. This finding may hint that the present IL is not dissociated in this water-rich region, despite the large dielectric permittivity of solvent water and as such it works as an extremely strong hydrophobe. An earlier 1-propanol (1P) probing study showed that [P4,4,4,4]+ is a significant amphiphile with a strong hydrophobicity and an equally strong hydrophilicity, and CF3COO- is a modest amphiphile. However, the 1-propanol (1P) probing methodology effectively uses the fourth derivative of G, and is capable of providing deeper information on the effect of the test solute on H2O. To reconcile the present conclusion with the earlier observations described above, we propose to conduct the 1P-probing of the ionic liquid salt, [P4,4,4,4]CF3COO.

© 2016 Elsevier B.V. We determined the excess partial molar enthalpy and the excess partial molar volume, HTFEE, VTFEE, of 2,2,2-trifluoroethanol (TFE) in TFE-H2O at 25.0 °C. We then evaluate the TFE-TFE interactions in terms of enthalpy and volume, HTFE-TFEE and VTFE-TFEE, graphically without resorting to any model dependent fitting functions. Both model-free third derivatives indicate that TFE is a hydrophobic solute and that as other hydrophobic alkyl mono-ols there are three distinct mixing schemes, Mixing Schemes I, II, and III in their aqueous solutions. The relative strength in hydrophobicity between TFE and tert-butylalcohol (TBA), for example, gave a mixed message within the behavior of these third derivative quantities. We thus applied the 1-propanol (1P) probing methodology (Koga, Y. Phys. Chem. Chem. Phys. 2013, 15, 14548) that utilizes the fourth derivative in effect, and quantified the degree of hydrophobicity of TFE. It turned out that TFE is a stronger hydrophobe than 1P and ethanol (ET), and has approximately the same hydrophobicity as TBA within the estimated uncertainty. These findings were compared with the ability reported in literature to denature β-lactoglobulin and to induce α-helices in melittin in their aqueous solutions.

© 2016 American Chemical Society. Biological sensing technology utilizing nanoparticles extends through a diverse range of fields. The nanosensing is controlled using the assembly/disassembly of nanoparticles dominated by interaction forces between them. Although the interaction potential surface gives decisive information on the sensing mechanism, evaluating the quantitative profile has been impossible due to extremely complicated interactions of conjugated soft matter. In this study, a model-potential-free determination of the interaction potential surfaces was devised by combining small-angle scattering and liquidstate theory. The model-potential-free liquid theory was developed for colloidal nanoparticles inherently with strong van der Waals attraction forces by their nanoscopic size. The present method extracts interaction potential between nanoparticles even in systems with complicated interactions due to conjugated soft matter. By applying this determination method to a glutathione-triggered biosensing reaction, interaction potential curves between biosensing nanoparticles were realized for the first time. The analysis revealed peculiar potential surfaces of the sensing nanoparticles. The mechanism of colorimetric nanosensing function based on surface plasmon resonance is discussed from the viewpoint of the assembly/disassembly of nanoparticles in nanocomposites dominated by the interaction potential surfaces.

© 2015 Elsevier B.V. All rights reserved. This study presents the development of large-area (18 cm × 18 cm × 2 cm), high refractive index (n ∼ 1.05) hydrophobic silica aerogel tiles for use as Cherenkov radiators. These transparent aerogel tiles will be installed in a Cherenkov detector for the next-generation accelerator-based particle physics experiment Belle II, to be performed at the High Energy Accelerator Research Organization (KEK) in Japan. Cracking has been eliminated from the prototype aerogel tiles by improving the supercritical carbon dioxide (scCO2) extraction procedure when drying the wet gel tiles. Finally, a method of mass-producing aerogel tiles for the actual detector was established. It was confirmed that the experimentally manufactured aerogel tiles meet the required optical and hydrophobic characteristics and have a uniform tile density.

© 2015 American Chemical Society. Small-angle X-ray scattering (SAXS) analyses of an asphaltene (a heptane-insoluble fraction in Canadian oil sand bitumen (CaAs)) at various concentrations in bromobenzene (BB) were performed at a synchrotron facility. BB is the first trial medium in which the aggregation behavior of asphaltenes has been elucidated, and is considered to be one of the "best" pure solvents for CaAs when determining the Hansen solubility parameters (HSP). Although the aggregation behavior of the CaAs in toluene (TL) and toluene-pentane mixed solvent (TL-PT10, containing 10% pentane on a volume basis) was confirmed to be similar to that reported in previous SAXS studies, the behavior in BB was markedly different. The results indicated that aggregates with a soft boundary of ∼30-60 Å in the radius of gyration (R<inf>g</inf>), which were observable in TL and TL-PT10, disappeared in BB and larger aggregates with a clear boundary appeared simultaneously. This phenomenon supported a colloidal aggregation model, with HSP analyses suggesting that BB dispersed the colloid surface fraction at the molecular level and isolated the colloid core fraction, which led to the formation of a rigid aggregation of the core fraction. The HSP analyses enabled us to evaluate the aggregation behavior quantitatively, and the results obtained by SAXS were consistent with those obtained by Rayleigh scattering that we reported previously.

© the Owner Societies 2015. Aqueous solutions of tetrabutylphosphonium trifluoroacetate, [P4444]CF3COO, exhibit a liquid-liquid phase transition with a lower critical solution temperature. Herein, we characterized the constituent ions, [P4444]+ and CF3COO-, in terms of their effects on the molecular organization of H2O on the basis of 1-propanol probing methodology devised by Koga et al. The resulting characterization of the hydrophobicity/hydrophilicity is displayed on a two-dimensional map together with previous results, for a total of four cations and nine anions of typical ionic liquid (IL) constituents. The results indicate that [P4444]+ is the most significant amphiphile with strong hydrophobic and equally strong hydrophilic contributions among the group of constituent cations of ILs studied so far. The hydration number for [P4444]+ was evaluated to be nH = 72, which is three times larger than that of a typical imidazolium-based cation, [C4mim]+. Self-aggregation of [P4444]+ was found to occur in an aqueous solution of [P4444]CF3COO above 0.0080 mole fraction of the IL.

© 2015 Elsevier B.V. All rights reserved. Aqueous solutions of tetrabutylphosphonium trifluoroacetate ([P4444]CF3COO) exhibit a LCST-type phase transition with the critical point near 0.025 in mole fraction of [P4444]CF3COO at T = 302 K. The phase behavior of [P4444]CF3COO-water mixtures was investigated by evaluating their density fluctuations, which provide quantitative descriptions of the mixing states of the solutions. The concentration dependence of the density fluctuations was investigated at 293 and 301 K for the mixtures without distinguishing the components and for the individual components ([P4444]CF3COO and water). A drastic change in the mixing state was observed for the solution when the critical point was approached.

© 2015 The Chemical Society of Japan. The density of ionic liquid (IL) + CO2 systems was measured by X-ray absorption method and excess molar volume was evaluated to investigate the volumetric behavior under a CO2 absorption process up to 20 MPa. A V-shaped density plot was observed, and three types of expanded/compressed trends were classified based on the excess molar volume of the IL. The volumetric behavior of the IL strongly depends on the CO2 amount absorbed in the IL's cavities.

© 2014 Elsevier B.V. A small-angle X-ray scattering has been used to probe protein-protein interaction in solution. Conventional methods need to input modeled potentials with variable/invariable parameters to reproduce the experimental structure factor. In the present study, a model-free method for extracting the excess part of effective interaction potential between proteinmolecules in solutions over an introduced hard-sphere potential by using experimental data of small-angle X-ray scattering is presented on the basis of liquid-state integral equation theory. The reliability of the model-free method is tested by the application to experimentally derived structure factors for dense lysozyme solutions with different solution conditions [Javid et al., Phys. Rev. Lett. 99, 028101 (2007), Schroer et al., Phys. Rev. Lett. 106, 178102 (2011)]. The structure factors calculated from themodel-free method agree well with the experimental ones. The model-free method provides the following picture of the lysozyme solution: these are the stabilization of contact-pair configurations, large activation barrier against their formations, and screened Coulomb repulsion between the charged proteins. In addition, the model-free method will be useful to verify whether or not a model for colloidal system is acceptable to describing protein-protein interaction.

To extract protein-protein interaction from experimental small-angle scattering of proteins in solutions using liquid state theory, a model potential consisting of a hard-sphere repulsive potential and the excess interaction potential has been introduced. In the present study, we propose a model-potential-free integral equation method that extracts the excess interaction potential by using the experimental small-angle scattering data without specific model potential such as the Derjaguin-Landau-Verwey-Overbeek (DLVO)-type model. Our analysis of experimental small-angle X-ray scattering data for lysozyme solution shows both the stabilization of contact configurations of protein molecules and a large activation barrier against the formation of the contact configurations in addition to the screened Coulomb repulsion. These characteristic features, which are not well-described by the DLVO-type model, are interpreted as solvent effects. © the Owner Societies.

One of the most common constituent anions for room temperature ionic liquids (RTILs), BF4-, was characterized in terms of its effect on H2O using the so-called 1-propanol (1P) probing methodology developed by us earlier [PCCP, 15(2013) 14548-14565]. The results indicated that BF4- is quantitatively characterized as an amphiphile with weak hydrophobic and moderate hydrophilic contributions. These results were plotted on a two-dimensional map with hydrophobicity and hydrophilicity axes, H2O defining the origin. The melting point of 1-ethyl-3-methylimidazoliumtetrafluoroborate ([C2mim]BF4) was found within the trend that the larger the hydrophobicity and the hydrophilicity of the chosen counter anion, the lower the melting point of the resulting RTIL made of [C2mim]+ cation and the chosen anion. For the 1-butyl-3-methylimidazolium ([C4mim]+) based RTILs, however, redetermination of the melting point of the perfectly dry [C4mim]BF4 appears to be necessary. © 2014 Elsevier B.V.

We characterized the effects of K+ and Cs+ ions on the molecular organization of H2O by the 1-propanol probing methodology, previously developed by us (Phys. Chem. Chem. Phys. 2013, 15, 14548). The results indicated that both ions belong to the class of "hydration center", which is hydrated by 4.6 ± 0.8 and 1.1 ± 0.5 H2O molecules, respectively, and leave the bulk H 2O away from hydration shells unperturbed. Together with our previous results for the total of 7 cations and 11 anions, we display resulting characterization on a 2-D map and show a quantitative difference in their strength of the effects on H2O between anions and cations. © 2014 American Chemical Society.

We have performed single crystal X-ray diffraction analyses of two 1-alkyl-3-methylimidazolium hexafluorophosphate ([Cnmim]PF 6) salts, [C1mim]PF6, and [C 3mim]PF6. The thermodynamically metastable crystalline phase (β phase) of the former was obtained by crystallization from the melt in a capillary for the crystallographic analysis. Both the cation and the anion in the β phase of [C1mim]PF6 show higher point group symmetry than those in the stable α phase. This result is shown to be consistent with the fact that the melting point of the β polymorph (314 K) is significantly lower than that of the α polymorph (364 K). The crystal structure of [C3mim]PF6 seems to be typical of that characteristic of the crystals of imidazolium-based room temperature ionic liquids. The cation conformation is the one in between those characteristic of the crystal structures of [C2mim]PF6 and [C 4mim]PF6. When taken together, all crystallographic data for the [Cnmim]PF6 series (n = 1-4) demonstrate the influence of the alkyl chain length dependence on structural packing in these salts. The free volume fractions for these structures are calculated and compared to the lattice energy simply based on formula unit volume. It is shown that the difference in the alkyl chain length of the imidazolium cations does not monotonically change with the lattice energy of the crystal structure, and the latter also depends on the packing efficiency of the constituent ions in the structure. © 2013 American Chemical Society.

Toward understanding intermolecular interactions governing self-association of proteins, the present study investigated a model protein, myoglobin, using a small-angle X-ray scattering technique. It has been known that removal of the heme makes myoglobin aggregation-prone. The interparticle interferences of the holomyoglobin and the apomyoglobin were compared in terms of the structure factor. Analysis of the structure factor using a model potential of Derjaguin-Laudau-Verwey-Overbeek (DLVO) suggests that the intermolecular interaction potential of apomyoglobin is more attractive than that of holomyoglobin at short range from the protein molecule.

The growth kinetics of gold nanoparticles induced by the conformational collapse resulting from the coil-globule transition of thermoresponsive polymer was studied using small-angle X-ray scattering (SAXS) method. The growth process of aggregates and nanoparticles formed during the reaction was determined on the basis of distance distribution functions calculated from the SAXS profiles without having to approximate or simplify the actual structures. The size of aggregates and nanoparticles reached a maximum not in the final stage of the reaction but in the middle stage, indicating that shrinkage of the particles occurred in the growth process. The surface roughness increased up to the middle stage of the reaction and then significantly decreased in the final stage. Furthermore, the dependence of polymer concentration was also investigated. It was found that small particles were generated prior to the formation of main products, and size of the small particles was estimated to be ca. 7 nm in diameter. The results reveal that the formation process progresses mainly based on fusion of the small particles induced by the structural collapse of polymer. Finally, the growth mechanism is discussed in detail. © 2013 American Chemical Society.

This paper proposes a new X-ray radiographic technique for measuring density uniformity of silica aerogels used as radiator in proximity-focusing ring-imaging Cherenkov detectors. To obtain high performance in a large-area detector, a key characteristic of radiator is the density (i.e. refractive index) uniformity of an individual aerogel monolith. At a refractive index of n=1.05, our requirement for the refractive index uniformity in the transverse plane direction of an aerogel tile is δ(n-1)/(n-1)<4% in a focusing dual layer radiator (with different refractive indices) scheme. We applied the radiographic technique to evaluate the density uniformity of our original aerogels from a trial production and that of Panasonic products (SP-50) as a reference, and to confirm they have sufficient density uniformity within ±1% along the transverse plane direction. The measurement results show that the proposed technique can quantitatively estimate the density uniformity of aerogels. © 2012 Elsevier B.V.

Asphaltene dispersed in toluene at 10-500 mg/L was analyzed using small-angle X-ray scattering (SAXS) with synchrotron radiation. The degree of fluctuation in the solutions showed a discontinuous maximum at 50 mg/L. Distance distribution function (DDF) analysis of the SAXS profiles suggested that the asphaltene formed a complex aggregated structure at 50 mg/L, whereas rodlike structures formed at 100 and 500 mg/L. The results indicate that 50 mg/L is a specific concentration on asphaltene aggregation state in toluene.

Transglycosylated rutin (Rutin-G), a newly developed transglycosylated food additive, was used as a novel excipient for improving the dissolution and absorption properties of flurbiprofen. No surface activity was found up to 100 mg/mL of Rutin-G concentration. No cytotoxicity to Caco-2 cells was observed even at a high level of 100 mg/mL Rutin-G solution. 1H NMR study with concentration variation revealed that Rutin-G formed small aggregates in water, with the aggregation number of Rutin-G above the critical aggregation concentration of about 5.0 mg/mL being 4. Structural analyses by small-angle X-ray scattering determined the aggregate to be several nanometers in maximum length. A solubility test of flurbiprofen in the presence of Rutin-G showed that the amount of dissolved flurbiprofen increased in proportion to the amount of Rutin-G loaded. This finding indicated a stoichiometric relationship between flurbiprofen and Rutin-G. The spray-dried particles of flurbiprofen/Rutin-G showed a significantly higher dissolution rate and greater absorption profile compared with the commercial flurbiprofen powder. Taken together, the results indicate the potential application of Rutin-G in the formation of a novel nanostructure of drug/transglycosylated material. © 2012 Elsevier B.V. All rights reserved.

Fluctuation terms of the supercritical aqueous solutions of n-pentane, i.e., those of densities, concentrations, and their correlation terms, were evaluated by small-angle X-ray scattering intensity in combination with isothermal compressibility and partial molar volumes. The fluctuations increased significantly with the fluid density up to the region of middle density, ∼0.2 g cm -3, and then decreased at higher density. In the region where the fluctuations took maxima or minima, the density was lower than those of water critical density. The particle-number fluctuations of individual components obtained from the fluctuation terms show that water molecules are distributed more inhomogeneously than n-pentane, especially in the region of ∼0.3 g cm -3. © 2012 Elsevier B.V. All rights reserved.

A high-pressure sample holder made entirely of titanium and a titanium alloy was constructed for small-angle X-ray scattering (SAXS) measurement of ionic liquids pressurized with CO 2. It is designed to vary the path length precisely and perform stable operation at high temperature and pressure, while retaining a constant path length. An in situ beam-monitoring detector for the transmitted X-rays was redesigned and used. SAXS experiments were carried out for an imidazolium-based ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, pressurized and saturated with CO 2. Zero angle scattering intensities, I(0), which directly relate to the mesoscale structural fluctuation, are evaluated from the obtained SAXS intensities. Values of I(0) meaningfully change with the CO 2 solubility. By using the constructed apparatuses, the anomalous behavior of CO 2 dissolution into ionic liquids is clarified from the viewpoint of the mesoscale structural change of ionic liquids that fluctuated by dissolved CO 2. The present system for SAXS measurement is widely applicable to investigations on structural fluctuations of liquids, solutions including phase separated systems, which are the same as the ionic liquids and CO 2 mixtures, and amorphous solids under extreme conditions. © 2012 The Japan Society of Applied Physics.

We characterized the effects of ethanol (ET) and dimethyl sulfoxide (DMSO) on H2O within a limited H2O-rich region by the 1-propanol (1P)-probing methodology developed by us earlier. The results are displayed on a two-dimensional map with twin coordinates: one pertaining to hydrophobicity and the other to hydrophilicity. The locus of ET on this map was at a point in between methanol (ME) and 2-propanol (2P) as expected from our earlier findings by thermodynamic studies. That for DMSO, however, was surprisingly more hydrophilic than ME. Similar to N-methyl groups discussed recently (J. Phys. Chem. B2011, 115, 2995), it was argued that the methyl groups attached to the S atom are made susceptible for direct hydrogen bonding to the surrounding H 2O molecules due possibly to the electronegativity of the S atom. In view of these findings, we suggest caution to be exercised for the conventional general trend of taking any methyl groups to be "hydrophobic." © 2012 American Chemical Society.

Imprisoned palladium: A unique approach is developed to incarcerate metal clusters with strictly controlled n values within hollow silica nanoparticles. A Pd 12L 24 spherical complex is used as a template for the hollow silica synthesis. The incarcerated Pd 12L 24 core is calcinated to give (PdO) n oxide clusters and subsequently reduced to Pd n metal clusters within the protective hollow silica. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.