Nanoscale surface-enhanced resonance Raman scattering spectroscopy of single molecules on isolated silver clusters

Surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on isolated colloidal silver clusters has been studied down to the single-molecule level with a high-resolution confocal optical microscope equipped with a spectrometer and a cooled CCD-camera. At the single-molecule level the SERRS-spectra recorded as a function of time reveal inhomogeneous behaviour such as on/off blinking, spectral diffusion and intensity fluctuations of vibrational lines, and even splitting of some lines within the spectrum of one molecule.