Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Molecular Dynamics

CPP 37.6: Vortrag

Freitag, 29. Februar 2008, 11:45–12:00, C 230

Binding and Diffusion of individual dye molecules in ultrathin liquid films — •Daniela Täuber, Jörg Schuster, and Christian von Borczyskowski — Research G.: From local constraints to macroscopic transport, TU-Chemnitz, Institut für Physik, 09107 Chemnitz

The structure and dynamics of liquids close to solid interfaces is of central interest for numerous practical applications involving microfluidic structures. By tracking of single dye molecules we have been able to reveal details of the molecular structure of ultrathin liquid films on interfaces in previous work [1].

Molecular motion in thin liquid film is not purely diffusive but includes also temporary sticking or binding of probes to the solid surface. Based on a series of recent experiments we demonstrate that sticking probabilities as well as the diffusion constants of various dyes in ultrathin TEHOS films are slowly changing on a time scale of days. Although the two phenomena are strongly interconnected, we can show that they are caused by two independent processes, namely i) the thinning of the film due to evaporation, and ii) a change of the chemical composition of the surface which will lead to a decrease of the sticking probability a few days after sample preparation. A simple surface chemistry model is presented to explain those observations. In addition we show that thinning of the films is accompanied by a slow down of diffusional motion, which supports further our findings of a strongly anisotropic diffusion due to the layering structure of the films [1].

[1] J. Schuster, F. Cichos, Ch. von Borczyskowski: Euro. Phys. J. E. 12 (2003), 75-80