Adsorption of pyridine, γ‐picoline and isonicotinonitrile on Ag colloidal particles studied by surface‐enhanced Raman scattering spectroscopy

The surface-enhanced Raman scattering (SERS) spectra of pyridine and related compounds, γ-picoline and isonicotinonitrile, in Ag colloids were studied. Electron diffraction measurement indicated that the Ag colloidal particles are composed of Ag crystals. Models for the molecules adsorbed on Ag particles were proposed and the optimized geometries of the models were determined through calculations of the stabilization energies due to adsorption made for the models with Gaussian 98 using the Hartree–Fock theory with the 3–21G basis set. The normal vibrations of the molecules adsorbed on Ag particles were calculated using the optimized models and assignments of the vibrational bands of the SERS spectra were made. On the basis of the results obtained, it was concluded that (1) pyridine and related compounds are adsorbed on Ag particles through NAg bonds and (2) the N atoms of the molecules are bound to the pointed ends of the surface of Ag particles on adsorption. Copyright © 2004 John Wiley & Sons, Ltd.