New Measurement Method of Complex Electrophoretic Mobility of Charged Colloids by Quasi-Elastic Light Scattering

Abstract
A new measurement method of complex electrophoretic mobility µ* of colloidal particles in suspension was developed using a heterodyne technique of quasi-elastic light scattering under a sinusoidal electric field. The influence of diffusion was removed by squaring the time-domain signal of scattered light and we succeeded in accurate and highly sensitive measurement of µ* in a wide frequency range for the first time. The frequency dependence of µ* of latex particles was measured up to 50 kHz by this method. The relaxation of mobility due to anomalous double-layer polarization was observed above 1 kHz in the obtained spectrum.