Surface-enhanced Raman spectra of pyrazine, pyrimidine, and pyridazine adsorbed on silver sols

Abstract

Raman spectra of pyrazine, pyrimidine, and pyridazine adsorbed on silver sols have been obtained and compared with existing
\ndata from corresponding experiments on Ag electrode. These two techniques give similar results except for pyrazine for
\nwhich strong bands, observed only in the SER spectrum on the electrode, may be due to reduction products coadsorbed on
\nthe Ag surface. Chemisorption plays a role in the absorption of diazines as evidence of Ag-N bond formation was found
\nin the SERS of all three molecules. Both N atoms of pyridazine are bound to the substrate and this explains an enhancement,
\nfor the latter molecule, of 2 orders of magnitude larger than for the other two compounds. The presence of low-frequency
\nAg-N modes and predictions of surface selection rules support “edge on”, rather than flat, orientation of diazines on the
\ncolloidal particles.