OPTICAL PHENOMENA OF SINGLE SILVER CLUSTERS

摘要

A double pulse method was developed to prepare silver cluster ensembles of very narrow size distribution (typically 100 nm +/- 20 nm). The individual nanoparticles electroplated were investigated by confocal spectromicroscopy. Results of confocal Raman microscopy are shown in this paper. The following characteristic features were observed (ⅰ) only few particles are Raman active particles, (ⅱ) the intensity of Raman scattering from one single particle is comparable to that of the Rayleigh scattering, (ⅲ) so far Raman signals were observed only from groups of particles, no situation could be found were the light was emitted by one single particle, (ⅳ) typically, the Raman radiation is emitted from irregular surface structures like the necks between two particles agglomerated. A model is developed suggesting an explanation for the local nature and the extraordinary strong enhancement. In this model the surface enhanced Raman scattering is described as Rayleigh scattering with enforced frequency shift.