Surface-enhanced Raman scattering of tartaric and malic acids adsorbed on silver colloids

The geometry and conformation of the anions of tartaric and malic acids adsorbed on silver colloid surfaces have been derived from their SERS spectra. Malate ion interacts with colloidal silver at any pH value through one of its carboxylate groups, and the skeleton of the ion in its trans-conformations lies almost parallel to the metal surface. Tartrate ion behaves in turn in a similar way in acid medium, but in basic medium it lies almost perpendicular to the metal surface. Anomalous SERS spectra due to chemical transformations undergone by the absorbates, have never been observed.