Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 4: Colloids and Nanoparticles II: Effective Interactions

CPP 4.5: Talk

Monday, March 26, 2007, 15:15–15:30, H37

Effect of confinement on the structuring within colloidal suspensions: A comparison between theory and experiment — •Regine v. Klitzing, Dan Qu, Yan Zeng, and Sabine Klapp — TU Berlin, Stranski-Laboratorium, D-10623 Berlin

Small angle neutron scattering experiments at suspensions containing Silica particles show a structure peak which indicates interactions between the particles. The position of the structure peak scales with the concentration c with an exponent 1/3. In order to study the effect of geometrical confinement the solutions are confined between a microsphere and a flat interface in a Colloidal--probe AFM. Oscillatory forces are measured due to layer -- by -- layer expulsion of the particles. The period has the same value as the particle distance in the corresponding bulk solution calculated from the position of the structure peak. The addition of salt reduces the amplitude, i.e. the ordering of the particles, and the scaling exponent of the particle distance in dependence of the concentration. The latter effect is observed for the first time. All results can be perfectly fitted by a theoretical model assuming a DLVO potential.