SPR observation of adsorption and desorption of water-soluble polymers on an Au surface

The adsorption and desorption of water-soluble polymers on an Au surface were characterized by the use of two types of electrochemical surface plasmon resonance (SPR)-based sensing systems. The electrochemical flow-injection SPR system monitored a resonance angle shift induced by potential application or sample adsorption to an Au thin film, which is the sensing element of the SPR system. When some polymers, such as polylysine were injected, the SPR signal increased, which is attributed to the adsorption of polymers onto the Au surface. Though the signal increase ceased after the successive application of polymer solutions, it restarted when positive and negative potentials were applied to the Au. This result suggested that the potential application forced desorption of polymers from the Au surface. To confirm the electrochemical desorption of polymers, the electrochemical SPR imaging system was used. When potential was applied on the Au thin film having polymers previously spotted on its surface, the polymer dots disappeared from the image.