Surface Resonance Raman Spectroscopy SRRS

Instrumentation. The experimental setup is basically the same as the one employed in SERS. For obvious reasons—the wavelength of the used light should match electronic transitions (i.e. optical absorptions) of the species at the investigated interface or in the interphase—sources with several tunable wavelengths are preferred. Dye lasers or gas ion lasers showing several laser lines are the source of choice. 

Studied examples include dye molecules or other strongly colored molecules adsorbed on metal surfaces or other materials suitable to be used as electrodes (e.g. glassy carbon). In several studies transition metal complexes like porphyrines and tetraazaannulenes have been investigated [501-505]. An earlier, unfortunately rather incomplete and inconclusive report is available [345]. 

Raman spectra recorded under resonant or pre-resonant (i.e. the laser line is somewhat away from the optical absorption maximum) conditions were obtained for the bulk complex cobalt tetra-/7-methoxyphenylporphyrine Co(TMPP). 

Somewhat surprisingly, the authors fail to notice that resonance enhancement is operative despite the fact that they elaborate in detail on the UV-Vis spectroscopy of some transition metal complexes. 

These spectra were obtained with a smooth, polished surface. Thus no surface enhancement was effective. The molecules under investigation can alternatively be deposited onto roughened surfaces and the obtained spectra show a combination of surface and resonance enhancement. The method is called surface enhanced resonance Raman spectroscopy (SERRS). 

---