Interfacial characterization of mesoscopic particle suspensions by means of radiowave dielectric spectroscopy: a minireview

Heterogeneous systems, in particular aqueous suspensions of colloidal particles, are very complex systems characterized by a variety of dynamic processes, occurring at different length and time scales, that involve, in a very intruing manner, the structural properties of both the dispersed particles and the disperding medium. Over the last three decades, knowledge of the behavior of such systems has taken greatly advantage by dielectric spectroscopy techniques. This is due to the rapid growth of the technology that makes possible, both in the frequency domain and in the time domain, to acquire dielectric spectra in a very huge frequency interval, typically from 1 0 − 5 to 1 0 9  Hz, or, correspondly, in the time interval from 104 s to 10 ps. In this paper, we will consider several typical colloidal systems, such as aqueous liposome suspensions, ionic and non-ionic micellar solutions, biological cell suspensions. We will describe how dielectric spectroscopy technique can be employed to obtain information concerning the different electrical polarization mechanisms occurring at different time scales and the way to evaluate the structural parameters governing the mesoscopic behavior of these complex systems.