Surface-enhanced Raman spectroscopy using gold-core platinum-shell nanoparticle film electrodes: toward a versatile vibrational strategy for electrochemical interfaces.

The aim of this work is to further improve the molecular generality and substrate generality of SERS (i.e., to fully optimize the SERS activity of transition-metal electrodes). We utilized a strategy of borrowing high SERS activity from the Au core based on Au-core Pt-shell (Au@Pt) nanoparticle film electrodes, which can be simply and routinely prepared. The shell thickness from about one to five monolayers of Pt atoms can be well controlled by adjusting the ratio of the number of Au seeds to Pt(IV) ions in the solution. The SERS experimental results of carbon monoxide adsorption indicate that the enhancement factor for the Au@Pt nanoparticle film electrodes is more than 2 orders of magnitude larger than that of electrochemically roughened Pt electrodes. The practical virtues of the present film electrodes for obtaining rich and high-quality vibrational information for diverse adsorbates on transition metals are pointed out and briefly illustrated with systems of CO, hydrogen, and benzene adsorbed on Pt. We believe that the electrochemical applications of SERS will be broadened with this strategy, in particular, for extracting detailed vibrational information for adsorbates at transition-metal electrode interfaces.