Computer simulations of charged colloids in alternating electric fields

Zhou, Jiajia; Schmid, Friederike

doi:10.1140/epjst/e2013-02066-y

Cited by 14 publications

(8 citation statements)

References 122 publications

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“…37,38 On the contrary, if ion fluxes that are tangential to the colloidal surface are dominant, the induced dipole points in the same direction as the external electric field. 39,40 The corresponding relaxation mechanism is commonly referred to as ''concentration polarization'', ''a-relaxation'', or ''volume diffusion''. The characteristic frequencies for this mode can be estimated as follows.…”

Section: Polarization Of the Diffuse Double Layer Outside The Microgementioning

confidence: 99%

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Dielectric spectroscopy of ionic microgel suspensions

et al. 2016

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The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization effects, experimental spectra on PNIPAM-co-AA [poly(N-isopropylacrylamide-co-acrylic acid)] ionic microgel particles suspended in de-ionized water exhibit three well-separated relaxation modes, which are due to the polarization of the mobile charges within the microgel particles, the diffuse double layer around the particles, and the polymer backbone. Expressions for the full frequency dependence of the electrode-polarization contribution to the measured dielectric response are derived, and a theory is proposed for the polarization resulting from the mobile charges within the microgel. Relaxation of the diffuse double layer is modeled within the realm of a cell model. The net charge and the size of the microgel particles are found to be strongly varying with concentration. A very small value of the diffusion coefficient of ions within the microgel is found, due to a large degree of chemical association of protons to the polymer backbone.

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Section: Polarization Of the Diffuse Double Layer Outside The Microgementioning

confidence: 99%

“…as, [OH À ] = K w /[H + ], [HCO 3 À ] = K C 1 K CO 2 p CO 2 /[H + ], [CO 3 2À] = K C 1 K C 2 K CO 2 p CO 2 /[H + ] 2 .The ionic strength can thus be calculated once [H + ] is obtained as the (numerical) solution of eqn(40). The value of the constant K CO 2 p CO 2 at atmospheric pressure has been determined in ref 77.…”

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confidence: 99%

Dielectric spectroscopy of ionic microgel suspensions

et al. 2016

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“…Accordingly, a collective ensemble of charged colloids responds in an even more complicated way to an external electric field. In this special issue, electrokinetics will be accessed by experimental studies [26,27] by computer simulations [28,29] and by statistical theory [30].…”

Section: Electric Fieldsmentioning

confidence: 99%

Introduction to colloidal dispersions in external fields

Löwen

2013

Eur. Phys. J. Spec. Top.

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Progress in the research area of colloidal dispersions in external fields within the last years is reviewed. Colloidal dispersions play a pivotal role as model systems for phase transitions in classical statistical mechanics. In recent years the leading role of colloids to realize model systems has become evident not only for equilibrium situations but also far away from equilibrium. By using external fields (such as shear flow, electric, magnetic or laseroptical fields as well as confinement), a colloidal suspension can be brought into nonequilibrium in a controlled way. Various kinds of equilibrium and nonequilibrium phenomena explored by colloidal dispersions are described providing also a guide and summary to this special issue. Particular emphasis is put on the comparison of real-space experiments, computer simulations and statistical theories.

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“…The points with err-bars are simulation results.The solid lines give the prediction from the Maxwell-Wagner-O'Konski theory. The dashed lines are numerical solutions to the electrokinetic equations[101].Reprinted from Ref [113]…”

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Computer simulations of single particles in external electric fields

Zhou

Schmid

2015

Soft Matter

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Applying electric fields is an attractive way to control and manipulate single particles or molecules, e.g., in lab-on-a-chip devices. However, the response of nanosize objects in electrolyte solution to external fields is far from trivial. It is the result of a variety of dynamical processes taking place in the ion cloud surrounding charged particles and in the bulk electrolyte, and it is governed by an intricate interplay of electrostatic and hydrodynamic interactions. Already systems composed of one single particle in electrolyte solution exhibit a complex dynamical behaviour. In this review, we discuss recent coarse-grained simulations that have been performed to obtain a molecular-level understanding of the dynamic and dielectric response of single particles and single macromolecules to external electric fields. We address both the response of charged particles to constant fields (DC fields), which can be characterized by an electrophoretic mobility, and the dielectric response of both uncharged and charged particles to alternating fields (AC fields), which is described by a complex polarizability. Furthermore, we give a brief survey of simulation algorithms and highlight some recent developments.

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Computer simulations of charged colloids in alternating electric fields

Cited by 14 publications

References 122 publications

Dielectric spectroscopy of ionic microgel suspensions

Dielectric spectroscopy of ionic microgel suspensions

Introduction to colloidal dispersions in external fields

Computer simulations of single particles in external electric fields

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