Alternating strings and clusters in suspensions of charged colloids

Everts, Jeffrey C.; Linden, Marjolein N. van der; Blaaderen, Alfons van; Roij, René van

doi:10.1039/c6sm01283c

Cited by 8 publications

(10 citation statements)

References 61 publications

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“…As an outlook, I propose extending the theory with (manybody) charge regulation [51,73,[75][76][77] and renormalization [78][79][80][81] to incorporate more types of electrostatic boundary conditions and nonlinear screening, respectively. The expressions of this paper can then still be used with the bare charge replaced by an effective (renormalized) charge.…”

Section: Discussionmentioning

confidence: 99%

Screened Coulomb interactions of general macroions with nonzero particle volume

Everts

2020

Phys. Rev. Research

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A semianalytical approach is developed to calculate the effective pair potential of rigid arbitrarily shaped macroions with a nonvanishing particle volume, valid within linear screening theory and the mean-field approximation. The essential ingredient for this framework is a mapping of the particle to a singular charge distribution with adjustable effective charge and shape parameters determined by the particle surface electrostatic potential. For charged spheres, this method reproduces the well-known Derjaguin-Landau-Verwey-Overbeek (DLVO) potential. Further exemplary benchmarks of the method for more complicated cases, like tori, triaxial ellipsoids, and additive torus-sphere mixtures, leads to accurate closed-form integral expressions for all particle separations and orientations. The findings are relevant for determining the phase behavior of macroions with experiments and simulations for various particle shapes.

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Section: Discussionmentioning

confidence: 99%

Screened Coulomb interactions of general macroions with nonzero particle volume

Everts

2020

Phys. Rev. Research

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“…For silica in water σ can vary between 10 −3 nm −2 and 10 nm −2 ; however, 5CB has a much smaller dielectric constant than water, so we expect lower surface charges. Similar dielectric (but isotropic) solvents reported surface charge densities between 10 −5 nm −2 and 10 −4 nm −2 for charged colloidal particles in cyclohexylbromide with dielectric constant = 7.92 [47,48], so we will use these as order of magnitude estimates for σ. Finally, we vary the Debye screening length κ −1 = λ D between 10 −9 m and 10 −5 m, based on estimated Debye screening lengths due to ionic impurities in some liquid crystals [35,49,50], or estimates of liquid crystals with doped ions [39,[51][52][53].…”

Section: Theorymentioning

confidence: 99%

“…z y m T w = = < / l a t e x i t > < l a t e x i t s h a 1 _ b a s e 6 4 = " W P p 2 4 5 behaviour [48,64], but it is also important in biological context. We use the Langmuir adsorption isotherms [65] and consider two different systems that are characterised by the following chemical reactions,…”

Section: Charge-regulation Effects On the Anchoring-strength Tunabilitymentioning

confidence: 99%

“…III. Therefore, charge regulation is of major interest in soft matter applications, from the charging behaviour of colloidal particles [37,[48][49][50][51][52], to the effect on interaction potentials [53], to phase behaviour [38,54], but it is also important in biological context. We use the Langmuir adsorption isotherms [55] and consider two different systems that are characterised by the following chemical reactions,…”

Section: Charge-regulation Effects On the Anchoring-strength Tunabilitymentioning

confidence: 99%

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Charge-, salt- and flexoelectricity-driven anchoring effects in nematics

Everts

Ravnik

2020

Liquid Crystals

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We investigate the effects of electric double layers and flexoelectricity on the surface anchoring in general nematic fluids. Within a simplified model, we demonstrate for a nematic electrolyte how the surface anchoring strength can be affected by the surface charge, bulk ion concentration and/or flexoelectricity, effectively changing not only the magnitude of the anchoring but also the anchoring type, such as from planar to tilted. In particular, we envisage possible tuning of the anchoring strength by the salt concentration in the regime where sufficiently strong electrostatic anchoring, as controlled by the (screened) surface charge, can compete with the non-electrostatic anchoring. This effect is driven by the competing energetic-torque couplings between nematic director and the emergent electrostatic potential, due to surface charge, ions and flexoelectricity. Our findings propose a way of influencing surface anchoring by using electrostatic effects, which could be used in various aspects, including in the self-assembly of colloidal particles in nematic fluids, optical and display patterns, and sensing.

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“…The concept of charge renormalisation 24,25 was, for example, introduced to overcome the limitation of low electrostatic potentials by including non-linear effects. Furthermore, analytical and numerical extensions have been made to include many-body effects [26][27][28][29] , charge regulation [30][31][32][33] , fluctuations [34][35][36] , ion-specific dispersion interactions 37 , nonadditivity 38 , and a zoo of so-called "non-DLVO forces" 39 , to just name a few, although this might lead to loss of transparency of the original simple theory.…”

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confidence: 99%

Anisotropic electrostatic screening of charged colloids in nematic solvents

Everts,

Senyuk,

Mundoor

et al. 2020

Preprint

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Charged systems where ions, DNA, proteins and/or charged colloidal particles are dispersed in an isotropic fluid, are found in a range of prominent materials and biological systems. However, generally the role of the host material dielectric anisotropy in charged colloidal materials is ignored, despite frequent relevance in defining colloidal self-assembly, biological function and outof-equilibrium behaviour. In this work, we formulate and experimentally demonstrate anisotropic electrostatic interactions in a system of charged colloidal particles in a nematic electrolyte. Experimentally, charged dumpling-shaped near-spherical colloidal particles are used as a model system of charged colloidal particles in a nematic medium, demonstrating anisotropic elastic and electrostatic effective pair interactions for colloidal surface charges tunable from neutral to high. Theoretically, we derive asymptotic expressions for (i) the anisotropic electrostatic potential on the single-particle level and (ii) the effective pair interaction in the system, under the assumption of spherical charged particles in a uniform nematic director field. The analytical expressions for the pair interactions are compared with experiments, demonstrating good qualitative agreement within an experimentally accessible parameter range. More generally, our work extends the traditional Derjaguin-Landau-Verwey-Overbeek (DLVO) theory for charge-stabilised colloidal suspensions in isotropic solvents, to dielectric anisotropic host media with orientational elasticity.

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Alternating strings and clusters in suspensions of charged colloids

Cited by 8 publications

References 61 publications

Screened Coulomb interactions of general macroions with nonzero particle volume

Screened Coulomb interactions of general macroions with nonzero particle volume

Charge-, salt- and flexoelectricity-driven anchoring effects in nematics

Anisotropic electrostatic screening of charged colloids in nematic solvents

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