Extending surface plasmon resonance spectroscopy to platinum surfaces

Surface plasmon resonance spectroscopy (SPRS) provides insight into interfacial chemical or electrochemical processes regarding surface composition, thickness or reactivity, but is typically limited to Au, Ag or Cu surfaces that satisfy the surface plasmon resonance conditions. Here, we provide a quantitative electrochemical and SPRS study of sputtered thin film Au/Pt surfaces that allows designing hybrid films optimized for stable electrochemical Pt behavior and efficient Au plasmonic excitation. Simulations show that for a given Au layer thickness, there is an optimal Pt layer thickness that makes the corresponding Au∖Pt film perform best in the sense of SPRS angular resolution. Cyclic voltammetry data suggests that a minimum of 3 nm Pt layer thickness is required to form a pinhole-free adlayer on Au that shows Pt-like surface reactivity. As a result, the optimum Au∖Pt layer thickness combination lies in the range of 27∖3 nm for SPRS experiments on surfaces exhibiting Au optical and Pt (electro)chemical properties. The combined experimental and modelling approach paves the way for predictive design of optimized transition/nobel metal hybrid thin films for plasmon-based spectroelectrochemical applications.