Influence of Localized Surface Charge Distributions on the Dielectric Relaxation Spectra of Spherical Colloidal Particles in Aqueous Solution

The influence of localized charge distributions at the interfaces of spherical colloidal particles in aqueous suspension is discussed in the light of the effective medium approximation theory of heterogeneous systems. The approach is shown to give analytical results in the case of shelled particles with the presence of two distinct interfaces. The whole dielectric response of the system gives rise to different relaxation contributions, falling in different frequency regions and attributed to different polarization mechanisms, at a molecular level. In particular, the number and the strength of the dielectric relaxations associated with the presence of localized charges is discussed.