General electrokinetic model for concentrated suspensions in aqueous electrolyte solutions: Electrophoretic mobility and electrical conductivity in static electric fields

Carrique, F.; Roa, Rafael; Arroyo, Francisco J.; Delgado, A.V.

doi:10.1016/j.jcis.2015.05.023

Cited by 11 publications

(8 citation statements)

References 43 publications

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“…when the counter-ions of the charged particles start to dominate the small ion population [30]. This is reproduced in computer simulations [29] and theoretically understood in terms of the electrolyte concentration dependence of the zeta potential [31]. Together, the experimental observations seem to suggest the existence of a broad maximum in the density dependent mobility [30].…”

Section: Introductionmentioning

confidence: 70%

An empirical correction for moderate multiple scattering in super-heterodyne light scattering

Botin

Mapa

Schweinfurth

et al. 2017

The Journal of Chemical Physics

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Frequency domain super-heterodyne laser light scattering is utilized in a low angle integral measurement configuration to determine flow and diffusion in charged sphere suspensions showing moderate to strong multiple scattering. We introduce an empirical correction to subtract the multiple scattering background and isolate the singly scattered light. We demonstrate the excellent feasibility of this simple approach for turbid suspensions of transmittance T 0.4. We study the particle concentration dependence of the electro-kinetic mobility in low salt aqueous suspension over an extended concentration regime and observe a maximum at intermediate concentrations.We further use our scheme for measurements of the self-diffusion coefficients in the fluid samples in the absence or presence of shear, as well as in polycrystalline samples during crystallization and coarsening. We discuss the scope and limits of our approach as well as possible future applications. PACS: if neededCorresponding author: Denis Botin dbotin@uni-mainz.de 2 INTRODUCTIONMultiple scattering (MS) strongly affects studies of turbid colloidal suspensions using Laser light scattering. Depending on the degree of MS, several different sophisticated approaches have been taken to use, correct for, or suppress MS in studies on suspension dynamics. At very large turbidities and small optical path lengths, suspension dynamics can be determined using diffusive wave spectroscopy (DWS) [1[2]]. In the regime of low to moderate multiple scattering, index matching is regularly employed [3, 4, 5], but it is not easily applicable in water based systems. Further, optical path lengths may be shortened by utilizing fibre optics [6]. In addition, cross correlation schemes [7] were pioneered by Phillies in the early eighties [8] and further developed to two-color or 2D cross correlation schemes [9, 10]. This way the methods and theory developed for (single) dynamic light scattering in the time domain [11] could be used also in turbid samples. Alternatively, in frequency domain, special mode selective heterodyne instrumentation was developed and applied to Brilluoin scattering [12,13,14]. Both cross correlation and mode selection, however, afford complex instrumentation and data evaluation schemes. A much simpler instrumentation is needed for the statistical analysis of heterodyne speckle fields taken at different times providing information about the velocity field in the fluid in a given plane perpendicular to the optical axis [15]. This information can be extracted, either by measuring their cross-correlation function or by recovering the power spectrum corresponding to the difference between the two speckle fields. Multiple scattering in this approach is minimized by using confocal geometry [16]. Yet another simple approach is path length resolved low coherence interferometry, which also is a static heterodyne technique [17,18]. There a certain small path length can be selected which corresponds to a single back-scattering event. Then only singly scattered light i...

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Section: Introductionmentioning

confidence: 70%

An empirical correction for moderate multiple scattering in super-heterodyne light scattering

Botin

Mapa

Schweinfurth

et al. 2017

The Journal of Chemical Physics

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“…We present our results and compare them to previous findings. We then evaluate them using the standard electro-kinetic model (SEM) for realistically salt free conditions and constant surface charge density [16]. In the plateau region, we can give a consistent interpretation of our experimental mobilities assuming: i) a constant saturated CO 2 background, ii) a non-renormalized charge for the quartz cell wall, and iii) a renormalized charge for the carboxylate modified particles consistent with the one derived from conductivity.…”

Section: Introductionmentioning

confidence: 59%

“…In Fig. 2a we display power spectra for increasing n. A broad multiple scattering contribution appears for n ≥ 2×10 16 m −3 and gains in strength. It swallows the signal for n ≥ 4.5×10 16 m -3 (Fig.…”

Section: Electro-kinetic Measurementsmentioning

confidence: 99%

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Non-monotonic concentration dependence of the electro-phoretic mobility of charged spheres in realistic salt free suspensions

Botin

Carrique

Ruiz-Reina

et al. 2020

The Journal of Chemical Physics

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We considerably extended the accessible range of concentrations for optical investigations of colloidal electro-kinetics using super-heterodyne Doppler velocimetry with multiple scattering correction. We performed measurements of electro-phoretic mobility and DC conductivity of aqueous charged sphere suspensions under realistically salt free conditions covering more than three orders of magnitude in particle number densities, n, and up to transmissions as low as 40%. At low n, the mobility shows an increase with n, then plateaus at intermediate n, and finally decreases at large n. Our study reconciles previous experimental observations made on restricted concentration ranges, and thus demonstrates the existence of a generic density dependence of the electro-phoretic mobility. Comparison to state of the art electro-kinetic theory suggests its relation to a density dependent particle charge.

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“…With that aim, the so-called cell model will be used. This was first introduced by Kuwabara [ 38 ], and further elaborated by different authors [ 24 , 35 , 39 , 40 , 41 ]. It is based on the assumption that the cited interactions can be represented by assuming that a single particle is in a concentric sphere of solution, such that its radius b guarantees that the volume fraction of solids in the sphere (the cell) is the same as in the whole dispersion:

and the boundary conditions for the quantities of interest at

will determine the interactions.…”

Section: Modelmentioning

confidence: 99%

AC Electrokinetics of Salt-Free Multilayered Polymer-Grafted Particles

et al. 2020

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Interest in the electrical properties of the interface between soft (or polymer-grafted) nanoparticles and solutions is considerable. Of particular significance is the case of polyelectrolyte-coated particles, mainly taking into account that the layer-by-layer procedure allows the control of the thickness and permeability of the layer, and the overall charge of the coated particle. Like in simpler systems, electrokinetic determinations in AC fields (including dielectric dispersion in the 1 kHz–1 MHz frequency range and dynamic electrophoresis by electroacoustic methods in the 1–18 MHz range) provide a large amount of information about the physics of the interface. Different models have dealt with the electrokinetics of particles coated by a single polymer layer, but studies regarding multi-layered particles are far scarcer. This is even more significant in the case of so-called salt-free systems; ideally, the only charges existing in this case consist of the charge in the layer(s) and the core particle itself, and their corresponding countercharges, with no other ions added. The aims of this paper are as follows: (i) the elaboration of a model for the evaluation of the electrokinetics of multi-grafted polymer particles in the presence of alternating electric fields, in dispersion media where no salts are added; (ii) to carry out an experimental evaluation of the frequency dependence of the dynamic (or AC) electrophoretic mobility and the dielectric permittivity of suspensions of polystyrene latex spherical particles coated with successive layers of cationic, anionic, and neutral polymers; and (iii) finally, to perform a comparison between predictions and experimental results, so that it can be demonstrated that the electrokinetic analysis is a useful tool for the in situ characterization of multilayered particles.

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General electrokinetic model for concentrated suspensions in aqueous electrolyte solutions: Electrophoretic mobility and electrical conductivity in static electric fields

Cited by 11 publications

References 43 publications

An empirical correction for moderate multiple scattering in super-heterodyne light scattering

An empirical correction for moderate multiple scattering in super-heterodyne light scattering

Non-monotonic concentration dependence of the electro-phoretic mobility of charged spheres in realistic salt free suspensions

AC Electrokinetics of Salt-Free Multilayered Polymer-Grafted Particles

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