A new surface-enhanced Raman scattering system for C60 fullerene: Silver nano-particles/C60/silver film

Surface-enhanced Raman scattering (SERS) spectrum of very good quality of “silver nano-particles/C60/silver film” system was reported for the first time by using the pyridine as a intermediate to connect and nest the C60 molecules to the gap of silver nano-particles and silver film. Experiment results show that the ternary system of “silver nano-particles/C60/silver film” is very effective and active. Not only was the number of vibrational modes greatly increased, especially some modes that were forbidden in Raman spectrum, but also were the significant Raman bands splitted as well as frequencies up and down shifted, respectively, arising from symmetry lowering and selection rule relaxing of C60 induced by the silver surface. Furthermore, the splitting of the Raman modes is consistent with the calculation based on group theory. The adsorption of C60 molecules is oriented on pentagons of C60 on the silver surface. It is difficult to separate the contributions of the electromagnetic and chemical mechanisms to the great enhancement of the Raman signal. On the one hand, the silver nanoparticles modified on the silver film play an important role in magnifying the surface local electric field near the silver surface through resonant surface plasmon excitation. On the other hand, charge transfer factor may not be neglected.