Electrochemical Tuning of the Dielectric Function of Au Nanoparticles

The tunable dielectric response of Au nanoparticles under electrochemical bias can be interpreted in terms of changes in the surface charge density, surface damping, and the near-surface volume fraction of the nanoparticles that experience a modified dielectric function, as well as changes in the index of refraction of the surrounding electrolyte medium. Using experimental bias-dependent extinction measurements, we derive a potential-dependent dielectric function for Au nanoparticles that accounts for changes in the physical properties contributing to the optical extinction.