Regensburg 2010 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 47: Focus: Charge Effects in Soft and Biological Matter III (jointly with BP)
CPP 47.3: Talk
Friday, March 26, 2010, 11:00–11:15, H45
Detection of multilayer formation of charged macromolecules by field-effect devices: from experiment to theory — •Andrey Cherstvy1, Mariam Abouzar2, and Arshak Poghossian2 — 1IFF-2, FZ Jülich, Germany — 2IBN-2, FZ Jülich, Germany
Field-effect based semiconductor devices for label-free detection of adsorption of charged macromolecules are widely used for biosensor applications. The quantitative understanding of signals measured is however still missing in many cases. We use a capacitive electrolyte-insulator field-effect device for electrical detection of layer-by-layer adsorption of oppositely charged polyelectrolyte PE PSS/PAH chains onto the sensor surface [1]. We measure the thickness of PE layers formed as well as the changes in morphology and wetability of the modified sensor surface. We also study the effects of ionic strength on the sensor signal detected upon PE multilayer formation. We observe progressively decaying oscillations of the sensor potential upon repetitive PE adsorption. To analyze these zig-zag variations, we develop a theoretical model that accounts for the Debye screening by mobile ions within the PE layer. The model predicts that potential oscillations monitored by the sensor originate from the sign and the charge density of last PE layer. These variations depend strongly on bulk electrolyte concentration and physical parameters of PE multilayers. At lower salt, the oscillations predicted are much larger and more persistent with number of PE layers deposited. The magnitude and decay length of oscillations are in good agreement with experimental observations.
[1] A. G. Cherstvy et al., submitted to J. Phys. Chem. B.