A SERS study of 1-methyl-2-pyrrolidinone adsorbed on active silver surfaces

Surface-enhanced Raman scattering (SERS) spectra of 1-methyl-2-pyrrolidinone molecules adsorbed on rough silver surfaces have been obtained. A strong signal due to AgN vibrations has been found at 240 cm−1 from molecules chemically bonded at the silver surface. A band in the CH-stretching region has been used to quantify molecules present on top of the first layer as a consequence of weaker interactions. These latter molecules have been removed with distilled water, allowing evaluation of the ratio between the SERS cross-section for `physisorptionʹ and `chemisorptionʹ. A difference in the selection rules between normal Raman and SERS has also been found and briefly discussed.