Dresden 2014 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Charged Soft Matter I

CPP 44.5: Talk

Thursday, April 3, 2014, 10:30–10:45, ZEU 118

Impedance spectroscopy of ions at liquid-liquid interfaces — •Andreas Reindl and Markus Bier — Max Planck Institute IS and University of Stuttgart, Germany

One possibility to examine interfaces between two immiscible liquids is by means of impedance spectroscopy. In order to interpret the measured impedance spectra, frequently equivalent (electric) circuits where each element is intended to represent a certain microscopic process are fitted to the data. In this contribution we highlight two major problems with this procedure and propose a novel approach to avoid them. Both problems of the commonly used one-step fitting of impedance data are related to the phenomenon of actually obtaining circuit elements which lump bulk and interfacial properties together. This leads to the first, more technical problem of a possible overfitting of the bulk elements at the expense of an underfitting of the interfacial elements, which compromises the accuracy of the desired interfacial quantities. The second, more fundamental problem is related to the assignment of microscopic processes to circuit elements, which we show to be approximative in general and which requires ad-hoc interpretations for one-step fitting. In order to overcome both difficulties, we propose to disentangle bulk and interfacial circuit elements by means of a two-step fitting procedure, which we demonstrate for theoretically determined impedance data and which can be expected to be used similarly for real data.
Reference:
A. Reindl and M. Bier, Phys. Rev. E. 88, 052312 (2013).