Surface-Enhanced Raman Spectroscopy as a Probe of Adsorbate-Surface Bonding: Simple Alkenes and Alkynes Adsorbed at Gold Electrodes

摘要

The interaction of various alkenes with gold electrodes has been studied using surface-enhanced Raman spectroscopy (SERS). Large decreases, from 70 to 140/cm, were observed in the C-C double bond and C triple bond C stretching frequencies upon absoprtion which are attributed to absorbate-surface bonding involving these groups. The potential dependence of these SERS frequencies suggests that the Pi yield s (sigma band) overlap is more prevalent than the d yields pi* (pi bond) interaction. Carbon-hydrogen stretching vibrations, nu(C-H), as well as other skeletal modes were also detected for the absorbates; paraffinic, olefinic, and aromatic nu(C-H) modes could readily be distinguished although acetylenic nu(CH) modes were too weak to be detected. Generally, the most intense SERS bands relative to those in the bulk-phase spectra are associated with vibrations of the carbon-carbon double or triple bonds. Attempts to examine SERS of absorbated acetylene were thwarted by a spontaneous surface reaction yielding a film of polyacetylene.