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.

Investigation of benzene adsorption on different metal surfaces closer to a practical system appears to be avery important intermediate stage to utilize the conclusion obtained on single-crystal surfaces. In this paper, we studied the electrochemical adsorption behaviors of benzene on roughened Pt group electrodes usingsurface enhanced Raman spectroscopy (SERS). The effects of potential, surface roughness, and benzeneconcentration were investigated. Significant difference in surface Raman spectra of benzene on Ru, Rh, Pd,and Pt surfaces were found. On Pt surfaces, the parallel-chemisorbed benzene, the vertical dissociated chemisorbedbenzene, and the physisorbed benzene were observed, evidenced by the ring vibration mode appearingat 872, 1012, and 991cm-1, respectively. On Pd, only parallel-chemisorbed benzene and physisorbed benzenewere found. On Rh and Ru, the SERS signals were mainly from the parallel-chemisorbed benzene, with anextremely weak signal from the physisorbed benzene. The potential dependent study reveals that the parallelchemisorbedspecies interacts strongest with the substrate, while the physisorbed species can be easily removedat positive potentials. The models for the adsorbed benzene were given to account for the different types ofbenzene on these Pt group metals. The difference in the atomization heat of the four metals was used tointerpret the different interaction strength of benzene with Pt group metals.

The emphasis in the present study was placed on developing Raman spectroscopy into a versatile technique, whichoffers intriguing opportunities for investigating electrocatalytic reaction. Through the in-situ Raman spectroscopicstudy, with a confocal Raman microscope, on the methanol electrooxidation on platinum electrodes with varioussurface roughness, it has shown the advantage in obtaining the informative spectra during the surface reaction withhigh faradaic current. This is hard to be performed by the other spectroscopic methods that have to use the thin-layercell. The ability to obtain both the low frequency and the high frequency vibrations of Pt-C and C O bands allowsthe assignment of surface species unambiguously. The ease of studying the surface bonding, investigating highlyroughened surfaces with dark color and using high concentration electrolyte may provide a way to bridge the gapbetween the systems of fundamental research and practical applications. The results reveal the surface roughnesseffect on the electrooxidation process and provide clear evidence for the parallel oxidation mechanism.

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.

A Raman cell suitable for the study of solid/liquid/gas three-phase systems and that can work very efficiently onconfocal microprobe Raman systems was introduced. The influence of the environment on the adsorption behavior ofmodel molecule CO on Pt was investigated and different behaviors were observed in the aqueous solution compared tothe gas phase. A preliminary Raman measurement on the three-phase system was performed using methanol as a testingsolution. The diffusion of CO, a dissociate product of methanol, on the Pt electrode from the solution side to the gasside was observed.