A surface-enhanced Raman spectroscopic (SERS) study of pyrazine adsorbed on roughened Rh electrodeswas performed. Potential and concentration effects on the adsorption behavior of pyrazine were investigated.The SER spectra display four pairs of overlapping bands with the relative intensity of each pair being highlypotential dependent, which has not been observed on other metals. The orientation change of the adsorbedpyrazine from the end-on to N/

Tip-enhanced Raman spectroscopy (TERS) is based on the optical excitation of localized surfaceplasmons in the tip-substrate cavity, which provides a large but local field enhancement near the tipapex. We report on TERS with smooth single crystalline surfaces as substrates. The adsorbates wereCN ions at Au(111) and malachite green isothiocyanate (MGITC) molecules at Au(111) and Pt(110) using either Au or Ir tips. The data analysis yields Raman enhancements of about 4105 for CN andup to 106 for MGITC at Au(111) with a Au tip, probing an area of less than 100nm radius.

A method to produce a substrate suitable for surface-enhanced Raman study on the pure massive Rh electrodewas developed. The surface-enhanced Raman scattering (SERS) active Rh electrode with good stability,reversibility, and ease of preparation can be obtained by the control-current electrochemical roughening method.The surface enhancement factor was estimated to be 3 orders of magnitude. Such kind of enhancement allowsthe investigation of not only some molecules of large Raman cross-section (e.g., pyridine) but also othermolecules of very small Raman cross-section (like CO). This result shows that the Rh surface can be used asa useful substrate for the combined electrochemical and Raman study of some systems that are both offundamental and application interest.