Surface-enhanced Raman spectroscopy of amino acids adsorbed on an electrochemically prepared silver surface

Abstract

An electrochemically roughened silver surface, in conjunction with a Raman microprobe spectrometer, was used to obtain SER spectra of a suite of 19 l-amino acids. The spectra obtained were very different from previously reported SER spectra obtained from silver hydrosols of amino acids. Analysis of the spectra showed that adsorption of all amino acids was via the ionised carboxylate group, and that the side chain of most of the molecules was also in close proximity to the surface. The spectra also indicated that, in contrast, the amine terminus was protonated and relatively far from the surface. Sulfur-containing amino acids also interacted with the silver surface through their sulfur atoms.