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DY: Fachverband Dynamik und Statistische Physik

DY 54: Complex Fluids and Colloids, Micelles and Vesicles (joint session CPP/DY)

DY 54.8: Talk

Friday, March 31, 2023, 11:45–12:00, MER 02

Anomalous Screening Behavior of Nanometer-Sized Ions — •Thomas Tilger and Regine von Klitzing — Department of Physics, Technische Universität Darmstadt, Darmstadt, 64289, Germany

Natural colloidal dispersions have accompanied mankind in the form of blood or milk ever since. Besides this, artificial systems have gained a significant importance for our daily life during the last decades.

Therefore, it is of special interest to gain an understanding of which interparticle forces govern the stability of colloidal dispersions and how this stability can be tailored. The DLVO theory is a powerful framework to describe these interactions. While this description provides a good agreement with experimental data for small 1:1 electrolytes, larger deviations emerge for ions of higher valency and of larger dimensions. For a detailed examination of these border cases, we directly measure the forces between colloidal silica particles in aqueous electrolyte solutions containing nanometer-sized ions by the colloidal probe AFM (atomic force microscopy) technique.

Two different types of nano-ions were chosen as model systems, Keggin ions (silicotungstic acid, STA, a 1:4 system) and Terpyridine-Nickel-complexes with variable charge. Their electrostatic screening behavior reveals significant deviations between the calculated and measured ionic strengths, which indicates some unexpected phenomena.