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Alan R. Denton - One of the best experts on this subject based on the ideXlab platform.
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Structure and stability of Charged Colloid-nanoparticle mixtures
The Journal of chemical physics, 2018Co-Authors: Braden M. Weight, Alan R. DentonAbstract:Physical properties of Colloidal materials can be modified by addition of nanoparticles. Within a model of like-Charged mixtures of particles governed by effective electrostatic interactions, we explore the influence of Charged nanoparticles on the structure and thermodynamic phase stability of charge-stabilized Colloidal suspensions. Focusing on salt-free mixtures of particles of high size and charge asymmetry, interacting via repulsive Yukawa effective pair potentials, we perform molecular dynamics simulations and compute radial distribution functions and static structure factors. Analysis of these structural properties indicates that increasing the charge and concentration of nanoparticles progressively weakens correlations between Charged Colloids. We show that addition of Charged nanoparticles to a suspension of like-Charged Colloids can induce a Colloidal crystal to melt and can facilitate aggregation of a fluid suspension due to attractive van der Waals interactions. We attribute the destabilizing influence of Charged nanoparticles to enhanced screening of electrostatic interactions, which weakens repulsion between Charged Colloids. This interpretation is consistent with recent predictions of an effective interaction theory of Charged Colloid-nanoparticle mixtures.
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Mixtures of Charged Colloid and neutral polymer: influence of electrostatic interactions on demixing and interfacial tension.
The Journal of chemical physics, 2005Co-Authors: Alan R. Denton, Matthias SchmidtAbstract:The equilibrium phase behavior of a binary mixture of Charged Colloids and neutral, nonadsorbing polymers is studied within free-volume theory. A model mixture of Charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with nonadditive diameters and then onto an effective Asakura–Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter—the ratio of the polymer diameter to the effective Colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into Colloid-rich (liquid) and Colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attr...
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mixtures of Charged Colloid and neutral polymer influence of electrostatic interactions on demixing and interfacial tension
arXiv: Soft Condensed Matter, 2005Co-Authors: Alan R. Denton, Matthias SchmidtAbstract:The equilibrium phase behavior of a binary mixture of Charged Colloids and neutral, non-adsorbing polymers is studied within free-volume theory. A model mixture of Charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with non-additive diameters and then onto an effective Asakura-Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter -- the ratio of the polymer diameter to the effective Colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into Colloid-rich (liquid) and Colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attraction between electrostatically repelling macroions. Comparison with predictions of density-functional theory reveals a corresponding increase in the liquid-vapor interfacial tension. The predicted trends in phase stability are consistent with observed behavior of protein-polysaccharide mixtures in food Colloids.
M Oettel - One of the best experts on this subject based on the ideXlab platform.
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Multipole expansion of the electrostatic interaction between Charged Colloids at interfaces.
Physical review. E Statistical nonlinear and soft matter physics, 2008Co-Authors: A Domínguez, D Frydel, M OettelAbstract:The general form of the electrostatic potential around an arbitrarily Charged Colloid at a flat interface between a dielectric and a screening phase (such as air and water, respectively) is analyzed in terms of a multipole expansion. The leading term is isotropic in the interfacial plane and varies with d(-3) where d is the in-plane distance from the Colloid. The effective interaction potential between two arbitrarily Charged Colloids is likewise isotropic and proportional to d(-3), thus generalizing the dipole-dipole repulsion first found for point charges at water interfaces. Anisotropic attractive interaction terms can arise only for higher powers d(-n) with n > or =4. The relevance of these findings for recent experiments is discussed.
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Multipole expansion of the electrostatic interaction between Charged Colloids at interfaces.
Physical Review E, 2008Co-Authors: A Domínguez, D Frydel, M OettelAbstract:The general form of the electrostatic potential around an arbitrarily Charged Colloid at a flat interface between a dielectric and a screening phase (such as air and water, respectively) is analyzed in terms of a multipole expansion. The leading term is isotropic in the interfacial plane and varies with ${d}^{\ensuremath{-}3}$ where $d$ is the in-plane distance from the Colloid. The effective interaction potential between two arbitrarily Charged Colloids is likewise isotropic and proportional to ${d}^{\ensuremath{-}3}$, thus generalizing the dipole-dipole repulsion first found for point charges at water interfaces. Anisotropic attractive interaction terms can arise only for higher powers ${d}^{\ensuremath{-}n}$ with $n\ensuremath{\geqslant}4$. The relevance of these findings for recent experiments is discussed.
Matthias Schmidt - One of the best experts on this subject based on the ideXlab platform.
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Mixtures of Charged Colloid and neutral polymer: influence of electrostatic interactions on demixing and interfacial tension.
The Journal of chemical physics, 2005Co-Authors: Alan R. Denton, Matthias SchmidtAbstract:The equilibrium phase behavior of a binary mixture of Charged Colloids and neutral, nonadsorbing polymers is studied within free-volume theory. A model mixture of Charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with nonadditive diameters and then onto an effective Asakura–Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter—the ratio of the polymer diameter to the effective Colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into Colloid-rich (liquid) and Colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attr...
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mixtures of Charged Colloid and neutral polymer influence of electrostatic interactions on demixing and interfacial tension
arXiv: Soft Condensed Matter, 2005Co-Authors: Alan R. Denton, Matthias SchmidtAbstract:The equilibrium phase behavior of a binary mixture of Charged Colloids and neutral, non-adsorbing polymers is studied within free-volume theory. A model mixture of Charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with non-additive diameters and then onto an effective Asakura-Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter -- the ratio of the polymer diameter to the effective Colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into Colloid-rich (liquid) and Colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attraction between electrostatically repelling macroions. Comparison with predictions of density-functional theory reveals a corresponding increase in the liquid-vapor interfacial tension. The predicted trends in phase stability are consistent with observed behavior of protein-polysaccharide mixtures in food Colloids.
J Callejasfernandez - One of the best experts on this subject based on the ideXlab platform.
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Charged Colloid polymer mixtures a study on electrostatic depletion attraction
Journal of Chemical Physics, 2011Co-Authors: Miguel Pelaezfernandez, A Monchojorda, J CallejasfernandezAbstract:In this work, light scattering methods have been used to study the effect of adding Charged polymer chains on the structural and dynamic properties of a Charged Colloidal system. The experimental measurements of the static structure factor Scc(q) show that as the polymer concentration increases, the main peak moves to higher q-values, which is interpreted in terms of the electrostatically enhanced depletion attraction induced by the polymer. Moreover, we found that the shift of the peak depends on the interplay between two relevant length scales, the polymer radius of gyration, Rg, and the Debye length, κ−1. To reach these conclusions, the polymer reference interaction site model has been employed to explain the experimental results and to study how the effective depletion attraction depends on the polymer concentration, Rg and κ−1. Additionally, the measurements of the dynamic structure factor f(q, τ) indicate that the Colloidal diffusion increases with the polymer concentration. Both static and dynamic ...
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structure of Charged Colloid polymer mixtures
EPL, 2010Co-Authors: Miguel Pelaezfernandez, A Monchojorda, J CallejasfernandezAbstract:We use a light scattering technique to investigate the effect of adding non-adsorbing Charged polymers to a very dilute electrostatically stabilized Colloidal suspension at low electrolyte concentration. The experimental results show that, as the polymer concentration increases, the main peak of the Colloid-Colloid structure factor moves to higher q-values, which cannot be only due to the screening of the direct Colloid-Colloid electrostatic repulsion. We show that the Colloid-polymer electrostatic repulsions lead to enhanced depletion forces that have a strong influence on the Colloid structure, even for diluted suspensions. The experimental results are interpreted using the off-lattice Polymer Reference Interaction Site Model (PRISM), and very good agreement is found for all polymer concentrations.
Alois Würger - One of the best experts on this subject based on the ideXlab platform.
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Thermoelectric effect on Charged Colloids in the Hückel limit
The European physical journal. E Soft matter, 2008Co-Authors: Julien Morthomas, Alois WürgerAbstract:We study the thermophoretic coefficient DT of a Charged Colloid. The non-uniform electrolyte is characterized in terms of densities and diffusion currents of mobile ions. The hydrodynamic treatment in the vicinity of a solute particle relies on the Huckel approximation, which is valid for particles smaller than the Debye length, a ≪ \( \lambda\) . To leading order in the parameter a/\( \lambda\) , we find that the coefficient DT consists of two contributions, a dielectrophoretic term proportional to the permittivity derivative d\( \varepsilon\)/dT , and a Seebeck term, i.e., the macroscopic electric field induced by the thermal gradient in the electrolyte solution. Depending on the particle valency, these terms may take opposite signs, and their temperature dependence may result in a change of sign of thermophoresis, as observed in several recent experiments.
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Thermoelectric effect of Charged Colloids in the Hückel limit
European Physical Journal E: Soft matter and biological physics, 2008Co-Authors: Julien Morthomas, Alois WürgerAbstract:We study the thermophoretic coefficient D_{T} of a Charged Colloid. The non-uniform electrolyte is characterized in terms of densities and diffusion currents of mobile ions. The hydrodynamic treatment in the vicinity of a solute particle relies on the Hückel approximation, which is valid for particles smaller than the Debye length, a≪λ. To leading order in the parameter a/λ, we find that the coefficient D_{T} consists of two contributions, a dielectrophoretic term proportional to the permittivity derivative dε/dT, and a Seebeck term , i.e., the macroscopic electric field induced by the thermal gradient in the electrolyte solution. Depending on the particle valency, these terms may take opposite signs, and their temperature dependence may result in a change of sign of thermophoresis, as observed in several recent experiments.
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Transport in Charged Colloids driven by thermoelectricity
Physical Review Letters, 2008Co-Authors: Alois WürgerAbstract:We study the thermal diffusion coefficient DT of a Charged Colloid in a temperature gradient, and find that it is to a large extent determined by the thermoelectric response of the electrolyte solution. The thermally induced salinity gradient leads in general to a strong increase with temperature. The difference of the heat of transport of coions and counterions gives rise to a thermoelectric field that drives the Colloid to the cold or to the warm, depending on the sign of its charge. Our results provide an explanation for recent experimental findings on thermophoresis in Colloidal suspensions.