Vibrational Characterization of Synthetic Eumelanin by Means of Raman and Surface Enhanced Raman Scattering

Eumelanin biopolymer synthetized from L-DOPA has been characterized by Raman and Surface Enhanced Raman Spectroscopy (SERS). Although Raman spectra of eumelanin were scarcely resolved, SERS measurements of this biopolymer on nanostructured gold substrate, provided a large enhancement of vibrational peaks related to functional groups adherent to the substrate, so that well resolved vibrational spectra were obtained. The SERS peaks correspond to vibrational modes related to the monomeric units of eumelanin. So, SERS spectra can be used to identify the monomeric content of eumelanin and resolve the presence of vibrational modes which have been calculated and predicted according to different theoretical models and previously observed in vibrational spectra of single monomeric units.