Dielectric spectroscopy of bidisperse colloidal suspensions

Peter J Beltramo; Eric M Furst

doi:10.1016/j.jcis.2012.04.070

Dielectric spectroscopy of bidisperse colloidal suspensions

J Colloid Interface Sci. 2012 Aug 15;380(1):34-41. doi: 10.1016/j.jcis.2012.04.070. Epub 2012 May 8.

Authors

Peter J Beltramo¹, Eric M Furst

Affiliation

¹ Department of Chemical and Biomolecular Engineering, Center for Molecular and Engineering Thermodynamics, University of Delaware, Newark, DE 19716, United States. beltramo@udel.edu

PMID: 22658357
DOI: 10.1016/j.jcis.2012.04.070

Abstract

Dielectric spectroscopy is used to measure the complex permittivity of bidisperse colloidal suspensions over the frequency range 2.5 kHz ≤ ω/2π ≤ 10 MHz using the spectrometer design of Hollingsworth and Saville (A.D. Hollingsworth, D.A. Saville, J. Colloid Interface Sci., 2003). Dielectric spectra of monodisperse polystyrene spheres of two diameters (530 nm and 1 μm) are fit to electrokinetic theory using the surface charge density as an adjustable parameter. Quantitative agreement is found in the dielectric increment and also for the conductivity increment, after considering the effect of added counterions and nonspecific adsorption. Bidisperse suspension spectra are a linear superposition of each particle's dielectric response. The results provide a simple method to extend standard electrokinetic theory based on a single particle size to dilute suspensions with many particle sizes and verify the sensitivity of the spectrometer.