Adsorption of pyridine carboxylic acids on silver surface investigated by potential-dependent SERS

The potential-dependent surface enhanced Raman scattering (SERS) of the three-pyridine carboxylic acids (picolinic acid, isonicotinic acid and nicotinic acid) on polycrystalline silver electrode are studied in this paper. Their surface geometries may be detected from the high-quality potential-dependent SERS signals. With the varying of potential the adsorption behavior of picolinic acid is invariant, perpendicularly standing on the silver surface with both N-atom of the heteroaromatic ring and carboxylate group, while the adsorption behavior of isonicotinic acid and nicotinic acid may change. At higher potential values, both isonicotinic acid and nicotinic acid stand perpendicularly on silver surface via carboxylate group. At low potential values, the former lie flat on the silver surface and the latter edge on the silver surface via oxygen lone pair electrons. The probable reasons are given.