The primary electroviscous effect, free solution electrophoretic mobility, and diffusion of dilute prolate ellipsoid particles (minor axis = 3 nm) in monovalent salt solution

摘要

The prinical objective of the present work is the modeling of the primary electroviscouse effect of charged prolate ellipsoid models of low axial ratio. Other transport properties examined include (free solution) electrophoretic mobilities and translational diffusion constants. A numerical boundary elemental method is employed to solve the coupled Poisson, low Reynolds number Navier-Stokes, and ion transport equations. The methodology is first applied to the primary electroviscous effect of spheres with a centrosymmetric charge distribution and excellent agreement with independent theory is obtained. Specific model studies are also carried out for prolate ellipsoid models with axial ratios less than 4 and a minor axis equal to 3 nm. Most studies are carried out in aqueous NaCl solution (2 to 50 nM) to 20 deg C for a range of different particle charges, although limited results are also present in LiCl and KCl solution. The primary electroviscous efec for weakly charged prolate ellipsoids is smaller than that of a sphere under similar conditions. These studies are also carried out at high absolute particle charge. A comparison is made between the primary electroviscous effect and electrophoretic mobilities of prolate elliposids and corresponding spherical models.