Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 67: Gerhard Ertl Young Investigator Award (talks of the selected canditates)

O 67.5: Vortrag

Donnerstag, 25. März 2010, 12:30–13:00, H37

The structure of surfactants at the nanoscopic oil-in-water droplet interface and the consequence for the interfacial tension — •Sylvie Roke — Max-Planck Institute for Metals Research Heisenbergstrasse 3, 70569 Stuttgart, Germany

Surfactants such as sodium dodecylsulphate (SDS) can reduce the interfacial tension between bulk water and bulk n-hexadecane by 42 mM/m. Although it is commonly expected that interfacial tension lowering should also take place on the interface of nanoscopic oil droplets in water vibrational sum frequency scattering experiments indicate otherwise. Vibrational sum frequency scattering is a method that can be used to obtain local structural information from the chemical species present at the interface on nanoscopic oil droplets in water. In these measurements we have directly measured the adsorption of SDS onto hexadecane oil droplets with an average radius of 83 nm. We find that the interfacial density of adsorbed SDS is at least one order of magnitude lower than that at a corresponding planar interface. The derived maximum decrease in interfacial tension is only 5 mN/m.