The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Yasuhisa Adachi - One of the best experts on this subject based on the ideXlab platform.
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yield stress of mixed suspension of silica particles and lysozymes the effect of zeta potential and Adsorbed Amount
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Atsushi Yamaguchi, Motoyoshi Kobayashi, Yasuhisa AdachiAbstract:Abstract To investigate the interactions between colloidal particles in the presence of oppositely charged proteins, the yield stress of a mixed suspension of silica particles and lysozymes was measured as a function of lysozyme dose and pH. Further, the corresponding surface properties of silica particles covered with lysozymes were determined by measuring the Adsorbed lysozyme Amount and zeta potential. The present results indicated that an increase in the Adsorbed lysozyme Amount increases the zeta potential of silica particles from negative to positive through an isoelectric point. As expected from the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, the maximum value of yield stress is obtained around the isoelectric point and the yield stresses decrease with an increase in the zeta potential magnitude. However, the maximum yield stress depends on the pH, and yield stresses at the same zeta potential magnitude are different depending on the zeta potential sign even if the pH values are similar. That is, the relationship between yield stress and zeta potential is asymmetric with respect to the isoelectric point. These asymmetric results of the yield stress indicate the existence of non-DLVO forces, such as patch-bridging attraction and lateral repulsion between Adsorbed lysozymes, affected by the Adsorbed Amount of lysozyme. Our analysis suggested that the relative Adsorbed Amount, defined as the ratio of the Adsorbed Amount to the maximum Adsorbed Amount, can be used as a parameter to explain the asymmetric feature of the yield stress with respect to the zeta potential. In addition to the zeta potential, the surface occupation of Adsorbed substances is critical in controlling particle–particle interactions.
Don M Zebolsky - One of the best experts on this subject based on the ideXlab platform.
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investigation of quantitative relationship between Adsorbed Amount of solute and solvent concentration at relatively high solute con centration by frontal analysis in rplc
Chinese Journal of Chemistry, 2010Co-Authors: Yan Wang, Xindu Geng, Don M ZebolskyAbstract:In previous paper a new adsorption isotherm which relates the Amount of solute absorbed to the solvent concentration is pro-posed and simplified, and it only can be used at lower solute concentration. In this article the scope of the new adsorption isotherm is extended and the expressions with three and four parameters are obtained. The equations with multi-parameters are valid when the Adsorbed mounts are larger and show non-linear logarithmic relationships. Tests with a homologue of are-matic alcohols by frontal analysis in reversed phase liquid chro-matography demonstrate that the experimental results fit those equations well. In addition, the predicted values by the multi-parameters were found to fit the experimental values well also. The parameters have physical meaning only for the two-param-eter equation for the aromatic alcohols.
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quantitative relationship between Adsorbed Amount of solute and solvent composition
Thermochimica Acta, 2003Co-Authors: Yan Wang, Xindu Geng, Don M ZebolskyAbstract:Abstract A new adsorption isotherm that relates the Amount of solute Adsorbed to the solvent concentration is proposed. The new equation is derived from Geng and Shi’s stoichiometric displacement model for adsorption (SDM-A). The obtained equation may be simplified to an expression containing two parameters. The equation with two parameters, valid for low concentrations of solute, is a logarithmically linear relationship. The intercept contains a thermodynamic equilibrium constant of the solute displacing solvent from the adsorbent. The slope is the negative value of the stoichiometric displacement parameter (Z), the average total number of solvent molecules displaced from an active site on the adsorbent and from the solute. Tests with a homologous series of aromatic alcohols by frontal analysis in reversed phase liquid chromatography demonstrate that experimental results fit the equation well.
Atsushi Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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yield stress of mixed suspension of silica particles and lysozymes the effect of zeta potential and Adsorbed Amount
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Atsushi Yamaguchi, Motoyoshi Kobayashi, Yasuhisa AdachiAbstract:Abstract To investigate the interactions between colloidal particles in the presence of oppositely charged proteins, the yield stress of a mixed suspension of silica particles and lysozymes was measured as a function of lysozyme dose and pH. Further, the corresponding surface properties of silica particles covered with lysozymes were determined by measuring the Adsorbed lysozyme Amount and zeta potential. The present results indicated that an increase in the Adsorbed lysozyme Amount increases the zeta potential of silica particles from negative to positive through an isoelectric point. As expected from the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, the maximum value of yield stress is obtained around the isoelectric point and the yield stresses decrease with an increase in the zeta potential magnitude. However, the maximum yield stress depends on the pH, and yield stresses at the same zeta potential magnitude are different depending on the zeta potential sign even if the pH values are similar. That is, the relationship between yield stress and zeta potential is asymmetric with respect to the isoelectric point. These asymmetric results of the yield stress indicate the existence of non-DLVO forces, such as patch-bridging attraction and lateral repulsion between Adsorbed lysozymes, affected by the Adsorbed Amount of lysozyme. Our analysis suggested that the relative Adsorbed Amount, defined as the ratio of the Adsorbed Amount to the maximum Adsorbed Amount, can be used as a parameter to explain the asymmetric feature of the yield stress with respect to the zeta potential. In addition to the zeta potential, the surface occupation of Adsorbed substances is critical in controlling particle–particle interactions.
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Charging and aggregation behavior of silica particles in the presence of lysozymes
Colloid and Polymer Science, 2017Co-Authors: Yi Huang, Atsushi Yamaguchi, Tien Duc Pham, Motoyoshi KobayashiAbstract:To gain insight into the colloidal stability in the presence of proteins, we measured the electrophoretic mobility and aggregation rate constant of silica particles coated with lysozymes, and the Adsorbed Amount of lysozymes on the silica. We also examined model analyses, which are based on the Derjaguin, Landau, Verwey, and Overbeek theory with the effect of charge heterogeneity, to discuss the aggregation of lysozyme-coated silica. Our results show that lysozymes enhance the aggregation of silica when the lysozyme-coated silica is near the isoelectric point. When the Adsorbed Amount of lysozyme is low, the effect of charge-patch attractive force promotes the aggregation of silica. The effect of charge heterogeneity weakens with the increase of Adsorbed Amount of lysozyme. Our model which takes account of the effect of charge heterogeneity can capture the trend of the aggregation of silica in the presence of lysozyme qualitatively, but there are also large quantitative discrepancies between the theoretical prediction and experimental results. Further improvement is required to describe realistic charge heterogeneity and the effect of the surface coverage of lysozyme on the silica.
Esben Thormann - One of the best experts on this subject based on the ideXlab platform.
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surface forces between highly charged cationic polyelectrolytes Adsorbed to silica how control of ph and the Adsorbed Amount determines the net surface charge
Langmuir, 2018Co-Authors: Junhao Huang, Esben ThormannAbstract:Atomic force microscopy (AFM) and quartz crystal microbalance with dissipation (QCM-D) were employed to investigate the pH-dependent adsorption of poly(diallyldimethylammonium chloride) (polyDADMAC) to silica surfaces as well as the surface forces between these layers. It was found that polyDADMAC adopted a relatively flat conformation when Adsorbed to a silica surface and that the Adsorbed Amount increased with increasing pH. From the surface force measurements it is evident that the surface undergoes a charge reversal upon saturation with polyDADMAC, at the three different investigated pH values, and that some degree of charge regulation of the silica surface takes place during the adsorption process. Finally, the overcharging phenomenon is discussed in terms of a geometrical mismatch due to the different average spacing between the surface charges on the silica surface and the size of the DADMAC monomer.
Roland J.-m. Pellenq - One of the best experts on this subject based on the ideXlab platform.
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Molecular Simulation of Water Confined in Nanoporous Ca-silica
MRS Proceedings, 2020Co-Authors: Patrick A Bonnaud, Benoit Coasne, Roland J.-m. PellenqAbstract:This paper reports on a molecular simulation study of the thermodynamics, structure and dynamics of water confined at ambient temperature in charged silica nanopores of a width H = 10 and 20 A. The adsorption isotherms for water resemble those observed for experimental samples; the Adsorbed Amount increases continuously in the multilayer adsorption regime until a jump occurs due to capillary condensation of the fluid within the pore. Strong layering of water in the vicinity of the silica surfaces is observed as marked density oscillations are seen up to 8 A from the surface in the density profiles for confined water. Our results also indicate that the Ca 2+ counterions remain in a space close to the silica surface whatever the pore width and the Adsorbed Amount of water. For all pore sizes and Adsorbed Amounts, the self-diffusivity of confined water is lower than the bulk due to the strong hydrophilic nature of the pore surface. Our results also suggest that the self-diffusivity of confined water is sensitive to the Adsorbed Amount of water molecules.
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Molecular simulation of water confined in nanoporous silica.
Journal of Physics: Condensed Matter, 2010Co-Authors: Patrick A Bonnaud, Benoit Coasne, Roland J.-m. PellenqAbstract:This paper reports on a molecular simulation study of the thermodynamics, structure and dynamics of water confined at ambient temperature in hydroxylated silica nanopores of a width H = 10 and 20 A. The adsorption isotherms for water in these nanopores resemble those observed for experimental samples; the Adsorbed Amount increases continuously in the multilayer adsorption regime until a jump occurs due to capillary condensation of the fluid within the pore. Strong layering of water in the vicinity of the silica surfaces is observed as marked density oscillations are observed up to 8 A from the surface in the density profiles for confined water. Our results indicate that water molecules within the first Adsorbed layer tend to adopt a H-down orientation with respect to the silica substrate. For all pore sizes and Adsorbed Amounts, the self-diffusivity of confined water is lower than the bulk, due to the hydrophilic interaction between the water molecules and the hydroxylated silica surface. Our results also suggest that the self-diffusivity of confined water is sensitive to the Adsorbed Amount.
