Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 22: Poster: Charged Soft Matter
CPP 22.8: Poster
Mittwoch, 28. März 2012, 11:00–13:00, Poster A
AFM characterization of structural changes of polycation covered surfaces induced by hydroxyl radicals — •Florian Berg1, Stephan Block2, and Christiane A. Helm1 — 1Institut für Physik, Uni Greifswald, Felix-Hausdorff-Str. 6, 17487 Greifswald, Germany — 2ZIK HIKE, Uni Greifswald, Fleischmannstr. 42 - 44, D-17487 Greifswald, Germany
Positively charged, branched polyethylenimine (PEI) adsorbed onto silicon wafers are attacked by free hydroxyl radicals. AFM is used to image the PEI layers in air. After the radical attack the PEI layers show 1.3nm high plateaus (area fraction 5 %). With Colloid Probe technique, the force profiles between adsorbed PEI layers before and after the radical attack are measured in NaCl solution of different ionic strength. The force profiles of freshly deposited flat PEI layers show that an electrostatic repulsion dominates the interaction. After the radical attack we find both surface potential and surface charge are reduced by a factor of about two, while the Debye length remains unchanged.
Negatively charged colloidal gold nanoparticles are adsorbed onto the oppositely charged PEI. After the radical attack we find a reduction in saturation surface coverage consistent with the decreased surface charge. Additionally, the adsorption kinetics is slowed down suggesting that the PEI-layer is no longer a flat, compact layer.