The universal electro-optic response of charged colloids in low electrolyte suspensions

The large dielectric dispersion of colloids in the low-frequency range, related to polarization of the particle surface electric layer (the α-relaxation), has been a subject of scientific interest for decades. In recent papers we advanced the idea that the process of particle surface polarization is partially detected by a second low-frequency relaxation displayed in the frequency domain of particle rotation. The aim of the present paper is to argument this view more consistently. The second low-frequency relaxation is as universal as α-relaxation and closely related to it. It is more sensitive to variations in particle electrophoretic mobility than the α-relaxation. The paper discusses several aspects concerning the phenomenon: the reasons for its difficult identification as a universal effect; the procedures helping its analysis; and the basic features and the origin of the phenomenon.

Beside the widely studied large dielectric dispersion of charged colloids in the kilohertz domain (the α-relaxation), a second low frequency relaxation is displayed in the frequency domain of particle rotation. The two effects are in close correlation and are both related to the interface electric polarization of the colloid particles.Figure optionsDownload as PowerPoint slide