Surface and resonance enhanced micro-Raman spectroscopy of xanthene dyes at the single-molecule level

Surface enhanced resonance Raman spectra of various rhodamine dyes, of pyronine G and thiopyronine adsorbed on isolated silver clusters were recorded at the single-molecule level with a high-resolution confocal laser microscope equipped with a spectrograph and a CCD-detector. The comparison of the spectra shows that the xanthene chromophore dominates the surface enhanced resonance Raman scattering spectra and wavelength selective excitation shows that resonance excitation contributes significantly to the spectral enhancement.