Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 16: Poster: Colloids and Complex Liquids

CPP 16.18: Poster

Tuesday, March 27, 2012, 18:15–20:45, Poster A

Investigation of confinenment induced oscillatory forces in nanoparticle-suspensions by CP-AFM — •Sebastian Schön, Yan Zeng, and Regine von Klitzing — Stranski-Laboratorium, Department of Chemistry, TU Berlin, Strasse des 17.Juni 124, D-10623 Berlin

Thin films of nanoparticles suspensions show a layered ordering in the vicinity of the confining surfaces, giving rise to oscillatory changes in density and force. These originate from the entropic excluded volume effect and indicate a break in the translational symmetry of the bulk system. The study of oscillatory forces therefore serves as a direct means to understand the interactions between colloids and control their stability.

Force measurements have been performed by Colloidal Probe Atomic Force Microscopy (CP-AFM), where the colloidal probe on the cantilever and the substrate act as confining surfaces. Forces can be extracted form the deflection signal of the cantilever and are normalized with the radius of the colloidal probe.

In previous investigations the influence of particles concentration, size and ionic strength of the suspensions has been studied. Using Small Angle X-Ray Scattering (SAXS) good agreement of the characteristic lengths between confinement and bulk was demonstrated.

Latest research focus on effect of surface potential of the nanoparticles on the oscillatory forces investigating different systems of silica nanoparticles and micelles.