Density functional theory study of surface-enhanced Raman scattering spectra of pyridine adsorbed on noble and transition metal surfaces

Pyridine as a typical model molecule has been most extensively studied by SERS for three decades. However, there has not been a satisfactory explanation for the dramatic change of the relative intensity of the two main bands assigned to the total symmetric modes at 1008 and 1035 cm(-1) when pyridine was adsorbed on silver and many other metals. We performed a hybrid density functional theory study of the binding interaction and the Raman spectral properties of pyridine-metal clusters. The calculated Raman scattering factors of total symmetric modes for the pyridine-metal complexes indicate that the bonding interaction influences the relative Raman intensity of the vibrational modes. The surface bonding mechanism was analyzed on the basis of molecular orbital theory. It was also shown that the binding interaction will lead to geometric changes and result in metal-dependent surface Raman spectra. This theoretical approach could be helpful in using SERS to study surface chemistry, in particular to extract valuable information about surface bonding and adsorption through calculating and analyzing the relative intensity of SERS spectra. Copyright (c) 2005 John Wiley & Sons, Ltd.