An electric double layer of colloidal particles in salt-free concentrated suspensions including non-uniform size effects and orientational ordering of water dipoles

Abstract

The response of a suspension under a variety of static or alternating external fields strongly depends on the equilibrium electric double layer that surrounds the colloidal particles in the suspension. The theoretical models for salt-free suspensions can be improved by incorporating non-uniform size effects and orientational ordering of water dipoles neglected in previous mean-field approaches, which are based on the Poisson-Boltzmann approach. Our model including non-uniform size effects and orientational ordering of water dipoles seems to have quite a promising effect because the model can predict the phenomena like a heavy decrease in relative permittivity of the suspension and counterion stratification near highly charged colloidal particles. In this work we numerically obtain the electric potential, the counterion concentration and the relative permittivity around a charged particle in a concentrated salt-free suspension corrected by non-uniform size effects and orientational ordering of water dipoles. The results show the worth of such corrections for medium to high particle charges at every particle volume fraction. We conclude that non-uniform size effects and orientational ordering of water dipoles are necessary for the development of new theoretical models to study non-equilibrium properties in concentrated colloidal suspensions.

Field-Induced Assembly of sp-sp2 Carbon Sponges

“…This is because the neutral carbon constituent is surrounded by the liquid media and negatively charged Au NPs in this case. Metal NPs formed by laser ablation method in liquids are typically encircled by a double containment layer (DCL) [9]. The medium laser action leads to the decomposition of the amorphous carbon compound that is certified by a full disappearance of the D peak in Figure 2 and the transformations of G and D+G peaks into the bands characteristic of linear sp-chains and into shorter elements including even free atoms in the beam area.…”

“…Gold nanoparticles shown on a Figure A1b have been prepared by a laser ablation method in DI water [15]. Metal NPs formed by this method in liquids are typically encircled by a double containment layer [9]. Thus, gold nanoparticles may stay electrically charged for a long time.…”

Electrophoresis and electric conduction in a salt‐free suspension of charged particles

“…∂v r ∂θ = 0 (for the Kuwabara model) [11,27,32,33], (26) where v r and v θ are the essential components of the fluid velocity, τ rθ is the tangential stress, and U is the particle velocity to be determined. For the electrophoresis in a salt-containing suspension of dielectric spheres, the Happel and Kuwabara models result in comparable quantities in the particle mobility.…”

“…A salt-free solution is a liquid medium without added electrolyte but containing mainly a counterion species dissociated from the ionogenic groups at an adjoining solid surface [19][20][21][22]. Typical examples of the salt-free solution are nonpolar solvents in which the solubility of salt is very low [23,24] and aqueous solutions whose H + and/or OH − concentrations are much lower than the concentration of the counterions stemming from an adjacent solid surface [25,26]. The electrophoresis and electric conduction in a suspension of colloidal particles in salt-free solutions differ from those in solutions containing added electrolyte, since in salt-free solutions the counterions are condensed remarkably in the electric double layer surrounding a highly charged particle and the electrostatic screening effect disappears for a particle with low charge.…”

Electrokinetic flow and electric conduction of salt‐free solutions in a capillary

“…Salt-free solutions refer to fluid phases that contain no added salt but only counterions resulting from dissociation reactions occurring at the adjoining wall [13][14][15][16][17]. Typical examples of salt-free solutions include nonpolar solvents with little soluble salt [18,19] and aqueous solutions in which the concentrations of H + and/or OH − are negligible in comparison with the concentration of counterions dissociated from the confining wall [20,21]. The electrokinetic phenomena of salt-free solutions differ from those of salt-containing solutions.…”