Surface-enhanced Raman spectroscopy of Vitamin B12 on silver particles in colloid and in atmosphere

The surface-enhanced Raman scattering (SERS) spectra of Vitamin B12 molecules on silver surface in colloid and in atmosphere were obtained with very low laser power. The SERS on silver surface in atmosphere shows more intense enhancement with sharper and narrower Raman peaks compared with the SERS in colloid. The adsorption geometries of Vitamin B12 molecules were analyzed based on the SERS data. Vitamin B12 molecule is supposed to adsorb on the silver particle in colloid with the corrin ring plane nearly vertical to the surface, while Vitamin B12 molecule is supposed to adsorb on silver surface with the corrin ring plane tilted to the surface. This could be due to the water effect of the molecular conformation and the characteristic of silver particles.