Single molecule photo-bleaching observed by surface enhanced resonant Raman scattering (SERRS)

Single molecule photo-bleaching of Rhodamine 6G (RH6G) dye molecules is observed by surface enhanced resonant Raman scattering in gold (Au) colloids under double resonant excitation conditions. The effect is revealed through a breakdown in the normal exponential decay of the dye population at extremely low concentrations. Step-like structures in the decay of the Raman signals show that individual molecules are being destroyed as a function of time. This arrangement allows a study of photochemical degradation at single molecular level, and creates the possibility for the determination of absolute enhancement factors in the Raman cross-sections.