Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 51: Charged Soft Matter II
CPP 51.7: Vortrag
Donnerstag, 3. April 2014, 16:30–16:45, ZEU 118
The Effects of Reactive Oxygen Species on Single Polycation Layers — •Florian Berg1, Steffen Drache1, Stephan Block2, Reiner Hippler1, and Christiane A. Helm1 — 1Inst. f. Physik, Uni Greifswald, 17487 Greifswald, Germany — 2Chalmers University of Technology, Gothenburg, Sweden
During times of environmental stress (e.g., UV or heat exposure), levels of reactive oxygen species (ROS) can increase dramatically, causing cell damage. Here, the effects of the molecular changes of a polyelectrolyte functionalized surface are investigated.
Positively charged, branched polyethylenimine (PEI) adsorbed onto silicon wafers is attacked by free hydroxyl radicals. With AFM Colloid Probe technique, the surface forces between the PEI layers are measured. The force profiles show that freshly deposited PEI layers are flat, i.e., electrostatic repulsion dominates the interaction. After radical attack both surface potential and surface charge density are reduced by a factor of about two, while the Debye length remains unchanged. Force volume measurements show a homogeneous distribution of the surface charge on the μm scale. To probe the nm-scale, negatively charged gold nanoparticles (NP) are adsorbed. After radical attack we find a 10 % decrease of saturation coverage consistent with the decreased surface charge density if the electrostatic three-body interaction is considered. Nevertheless, the NP adsorption kinetics is slowed down suggesting that radical attacks induce inhomogeneities on the nm-scale.