Particle Size Dependence for Effective Charge Density of Ionic Colloids

Abstract

Particle size dependence of the effective surface charge density, sgr ^e, of colloidal silica particles, having radius a ranging from 16 to 60 nm, was examined by applying electrical conductivity measurements. sgr ^e markedly increased with decreasing a, and approached to the case for small ions, namely, sgr ^e=analytical (net) charge density, sgr ^a. sgr ^e was roughly proportional to 1/a, as expected from the mean field theories. However, leveling off of sgr ^e at high sgr ^a, which was expected from charge renormalization approach, was not observed.

Keywords:

• Surface charge density
• Electrical conductivity
• Ionic polymer latex
• Colloidal silica