Gap-mode Plasmon Enhanced Raman Spectroscopy for in-situ Observation of Atomically Flat Single Crystalline Metal Electrode Surfaces

摘要

Surface-enhanced Raman scattering (SERS) is widely utilized as a powerful spectroscopic tool for studying molecules adsorbed on metal surfaces, especially in electrochemical conditions. The signal enhancement of Raman scattering is mainly caused by field enhancement at a metal surface. Therefore, excitation of surface plasmon polaritons is the key issue in SERS events, and application of conventional SERS is limited to 'rough' metal surfaces. However, since various adsorption sites are exposed on such substrates, information of each adsorption site is not available and SERS spectra provide only averaged information. Besides, efficient plasmonic field enhancement is available only at coinage metals with rough surfaces such as Au, Ag, Cu, etc. Unfortunately, most of other metals, including catalytic metals such as Pt and Pd, are commonly considered to be non-SERS-active because of the large imaginary part of the dielectric constant.