Surface-enhanced Raman scattering (SERS) spectroscopy of enantiomeric and racemic methionine on a silver electrode-evidence for chiral discrimination in interactions between adsorbed molecules

The adsorption of enantiomeric and racemic forms of methionine on the silver electrode surface was studied by surface–enhanced Raman scattering spectroscopy (SERS) as a function of pH value of the solution and the electrode potential, as well. Results for d–methionine were analogous to these for l-methionine, as expected. However, in the case of racemic mixture of d,l-methionine in acidic pH the spectral effects were different than those observed for monolayers built of pure enantiomer (d or l). This effect was discussed in terms of interplay between surface-molecule and intermolecular interactions between adjacent methionine molecules at the Ag surface.