Electrophoretic Motion of a Spherical Particle with a Symmetric Nonuniform Surface Charge Distribution in a Nanotube

Abstract

The electrophoretic motion of a spherical nanoparticle, subject to an axial electric field in a nanotube filled with an electrolyte solution, has been investigated using a continuum theory, which consists of the Nernst-Planck equations for the ionic concentrations, the Poisson equation for the electric potential in the solution, and the Stokes equation for the hydrodynamic field. In particular, the effects of nonuniform surface charge distributions around the nanoparticle on its axial electrophoretic motion are examined with changes in the bulk electrolyte concentration and the surface charge of the tube's wall. A particle with a nonuniform charge distribution is shown to induce a corresponding complex ionic concentration field, which in turn influences the electric field and the fluid motion surrounding the particle and thus its electrophoretic velocity. As a result, contrary to the relatively simple dynamics of a particle with a uniform surface charge, dominated by the irradiating electrostatic force, that with a nonuniform surface charge distribution shows various intriguing behaviors due to the additional interplay of the nonuniform electro-osmotic effects.

Diffusiophoresis of an Elongated Cylindrical Nanoparticle along the Axis of a Nanopore

“…The mathematical model and its implementation with COMSOL have been extensively validated by comparing its results of electroosmotic, electrophoretic, and diffusioosmotic flows with the corresponding approximate analytical solution and experimental results obtained from the literature. [17,[55][56][57][58]61] In this section, we present a few numerical results of the diffusiophoretic motion of a charged elongated cylindrical nanoparticle in a nanopore as functions of the imposed concentration ratio, a, the ratio of the particle size to the EDL thickness, ka p , the dimensionless surface charge density of the particle, " s p , the particle aspect ratio, L p /a p , the ratio of the pore size to the particle's size, a/a p , the dimensionless surface charge density of the nanopore, " s w , and the type of salt. To show the effect of the induced electrophoresis driven by the generated electric field, E diffusivity , arising from the difference in the ionic diffusivities, salts KCl and NaCl at temperature T = 300 K are used.…”

Electrokinetic particle translocation through a nanopore containing a floating electrode

“…The axial particle velocity is determined on the basis of the balance of the force in the z à direction acting on the particle using a quasi-static method [39][40][41][42][43] …”

Effect of linear surface-charge non-uniformities on the electrokinetic ionic-current rectification in conical nanopores

“…A nanopore with a non-uniform surface-charge distribution would generate axial ionic-concentration gradients along the EDL, in addition to the electric potential gradients, even in the absence of the external electric field [33,34]. The induced field, in turn, can affect the ionic enrichment and depletion in the tip region through the interaction between the overall electric field and the inhomogeneous net charge in the EDL.…”