Fluctuating single sp 2 carbon clusters at single hotspots of silver nanoparticle dimers investigated by surface-enhanced resonance Raman scattering

Abstract

We evaluate spectral changes in surface enhanced resonance Raman scattering (SERRS) of near-single dye molecules in hotspots of single Ag nanoparticle (NP) dimers. During the laser excitation, surface enhance florescence (SEF) of dye disappeared and the number of SERRS lines decreased until finally ca. two lines remained around 1600 and 1350 cm-1, those are evidence of G and D lines of single sp2 carbon clusters. Analysis of the G and D line intensity ratios reveals the temporal fluctuation in the crystallite size of the clusters within several angstroms; whereas, broadening and splitting in the lines enable us for identifying directly the dynamics of various defects in the clusters. This analysis reveals that the detailed fluctuations of single sp2 carbon clusters, which would be impossible to gain with other microscopic methods.