Investigation of Temperature-Dependence of Zeta Potential Using Molecular Dynamics Simulation of Nanoscale Electroosmotic Flows

摘要

The objective of the present work is to investigate temperature-dependence of zeta potential in nanoscale electroosmotic flows (EOF). Molecular dynamics (MD) simulations for EOF is performed with a W-molecule used as an approximate model for water. To explore the influences of the particle mass, various electrolytes such as a fictitious model W{sub}±, the commonly used KCl and NaCl. At various temperature of the solid-fluid system, the present molecular dynamics (MD) results demonstrated that the conventional Smoluchowski equation is still valid in nanoscale electroosmotic flow but the temperature-dependence of the critical parameters such as electric permittivity and fluid viscosity have to be considered. At condition of low ion concentration, the electric double layer is thick and Smoluchowski equation is not appropriate. Physical mechanisms are explored in either viewpoint of EOF velocity or ions concentration. The present MD results demonstrate that (1) high bulk ion concentration leads to a decrease in zeta potential; (2) the sign of wall charge affects conterion concentration but the magnitude of zeta potential is little influenced; (3) high wall density enhances fluid slippage and in turn results in high fluid velocity and zeta potential; and (4) particle size has influences on the magnitude of zeta potential.