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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Complex Fluids, Colloids, Micelles and Vesicles (joint session CPP/DY)

CPP 44.5: Talk

Thursday, March 21, 2024, 16:45–17:00, H 0110

Screening Behavior of Nano-Ions in Aqueous Solutions — •Thomas Tilger and Regine von Klitzing — Department of Physics, Technische Universität Darmstadt, Darmstadt, 64289, Germany

Due to their special properties, which make them suitable for many applications, the interest in nano ions grew during the last years. They turned out to be promising new materials for e.g. wastewater treatment, separation of nuclear waste and to stabilize foams. Especially for the last application, it is crucial to understand how the interaction between nano ions and the interaction betweeen interfaces in the presence of nano ions can be described.

To directly measure the interaction between well-defined interfaces, colloidal probe atomic force microscopy (CP-AFM) has proven to be a powerful tool. As a model system for nano ions, we chose superchaotropic Keggin ions in aqueous solutions at different concentrations and investigated their influence on the interaction between colloidal silica beads.

It turned out that - despite their large size of approximately one nanometer - the interaction between the silica beads can still be described by the DLVO-theory of electrolyte solutions, consisting of a van der Waals attraction and an electrostatic double layer repulsion. However, the obtained screening lengths exhibit a significant deviation from the ones expected according to the nominal ionic strength of the solutions. The strength of this deviation increases with the concentration of the solutions and might be a hint for an ion aggregation.

Keywords: Colloidal Probe AFM; Surface Forces; DLVO Theory; Nano Ions; Keggin Ions