Graphene-Based in situ Electrochemical Plasmon Waveguide Resonance Sensor Incorporating a Polymer Layer

Surface plasmon resonance (SPR) sensing is a suitable analytical technique to obtain kinetic information about the solid–liquid interface. In the standard SPR configuration, a metallic structure is needed, and the sensitivity is limited to the region close to the metal surface. Hence, it is difficult to study electrochemical reactions free of the metal film. Here, the use of a polymer layer on the metal is proposed, which serves as a dielectric waveguide presenting additional modes due to plasmon waveguide resonance (PWR). This helps one to offset the analytical interface a few 100 nm away from the metal surface. For studying electrochemical reactions, a graphene sheet is incorporated as an electrode on top of the polymer waveguide, thereby completely decoupling the electrode from the plasmonic gold layer. As a proof-of-principle, the possibility of following the kinetics of nanoparticle growth and dissolution is demonstrated. Moreover, it is shown that the electrochemical PWR can be used to monitor the redox behavior of immobilized nanoparticles in situ during potential cycling. Although the chemical structural information is not obtained, the ability to extract in situ kinetic data will help us gather a deeper mechanistic understanding of active metal centers in the context of electrocatalysis.