Blinking Surface-Enhanced Raman Scattering and Fluorescence From a Single Silver Nanoaggregate Simultaneously Analyzed by Bi-Color Intensity Ratios and a Truncated Power Law

Surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF) occur on and near a noble metal surface, respectively. To investigate the molecular behavior on and near the surface of a noble metal, blinking SERS and SEF were simultaneously observed in different wavelength regions for a single Ag nanoaggregate. SERS of poly-L-lysine was not observed at the junction of the Ag nanoaggregate, whereas SEF was emitted by a Ag cluster. This behavior suggests single-molecule detection. The blinking statistics of SERS and SEF of stable adsorptive dye molecules were compared with those of unstable ones in terms of bi-color intensity ratios and a power law analysis. Although the fluctuation in the bi-color intensity ratio of the stable adsorbed dye was larger than that of the unstable one, the adsorbed dye can fluoresce even near the surface of the aggregate. The power law for SERS is truncated at the shorter tail compared to that for SEF. This may be due to a difference in the energy barrier between the nonemissive and emissive states.