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DS: Fachverband Dünne Schichten

DS 18: Symposium: In situ Optics I

DS 18.1: Hauptvortrag

Mittwoch, 28. März 2007, 15:00–15:30, H34

Analysis of protein layer structure using real-time ellipsometry — •Hans Arwin — Laboratory of Applied Optics, Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden

A thickness resolution in the sub-nm range and its in situ capability make spectroscopic ellipsometry (SE) suitable for studies of thin organic layers. Here SE used in internal reflection mode is reviewed and it is shown that SE exhibits pm-sensitivity for protein adsorption on thin metal layers if used at surface plasmon resonance conditions. With such large sensitivity a determination of the microstructure of adsorbed protein layers, e. g. in terms of mass distribution perpendicular to a surface, is within reach. Another implication is an increased sensitivity in biosensor applications.

The molecular structure of surface-bound proteins can be analyzed with SE in the infrared spectral region by determining the refractive index N=n+ik. In this way thermally induced structural changes can be monitored. This is of importance for future devices containing protein layers for which thermal stability is important. Studies on protein multilayers show that heating above 100 degrees influences the amide bands and at 200 degrees layer degradation seen as irreversible changes in n and k occur. Methodology and results from recent studies of effects of heating proteins monolayers are presented and possibilities to perform real-time in situ infrared SE is discussed.