Potential-driven changes in hydration of chitosan-derived molecular films on gold electrodes

Chitosan-derived molecular films self-assembled on the gold surface were characterized using electrochemical methods combined with quartz crystal microbalance, atomic force microscopy and surface enhanced infrared absorption spectroscopy. We have observed potential-dependent structural transitions, which involved a reorientation of the oligosaccharide molecules and either depletion or accumulation of water molecules within the film. The nature of water accumulated within the chitosanderived film varies with the potential but it is dominated by hydrogen-bonded species. The content of water entrapped within the oligosaccharide film can be controlled by the potential applied to the electrode, which means that its hydration/dehydration can be triggered by an electric field.