Studying the role of surface chemistry on polyelectrolyte adsorption using gold-thiol self-assembled monolayer with optical reflectivity.

Self-assembled monolayers of thiols on gold are employed to study the role of surface chemistry on adsorption of polyelectrolytes to solid substrates. The suitability of these substrates is demonstrated in optical reflectivity, which combines high sensitivity to the possibility to precisely control the hydrodynamic conditions at the solid/water interface. Therefore, this system allows the determination of both the adsorbed amount and the kinetics of adsorption. The behavior of two representative strong polyelectrolytes of opposite charge is discussed as a function of pH and of concentration of a monovalent electrolyte in aqueous solutions. The application of equivalent substrates with varying surface chemistry sheds light on the role of different energetic contributions driving polyelectrolyte adsorption.