Electrochemical SERS of Flavin on a Gold Surface

Surface-enhanced Raman scattering (SERS) spectroscopy has received a great deal of attention for its utility as a sensitive technique for chemical. Noble metal nanoparticles (NPS) (Au, Ag and Cu) are the most commonly used SERS substrates both in colloidal solutions and on solid surfaces1. They have advantages such as ease of formation and handling, and tunable size and shape dependent optical properties. Electrochemistry of redox enzymes is of current interest because of the potential application in bioelectronics and biosensors. Detailed information, that is, conformation, orientations, as well as active sites for adsorbates, is beyond the resolution of electrochemistry, while the technique of surface-enhanced Raman Spectroscopy (SERS) could provide molecular level information for the molecules at the interface. Small molecular cofactors (ligands) are essential for cells to perform numerous biological functions. To understand the mechanism by which these ligands effect protein function, is it important to identify ligand-binding and in the present work, we will report the results of studies on the interaction of Dinucleótido de Flavina e Adenina (FAD) on a gold electrode. In the solid FAD spectrum (Fig. 1 (a)) the strongest Raman signal as observed. Xiao et al.2 have obtained the SERS spectra of FAD. Under positive polarization, the main characteristic of SERS for FAD is the appearance of peaks at 1353 cm-1 (CN, C), 1373 cm-1 (CNCC), CH3), 1449 cm-1 (CN), 1499 cm-1 (CN,CC) e 1511 cm-1 (CN,CO) and on a negatively charged electrode at 1499 cm-1 (CN,CH3), 1739 cm-1 (CN,CC) e 1623 cm-1 (CN,CO). In addition, a strong band near 1350 cm-1 is assignable to the Flavin3. The SERS of FAD shows a strong potential dependence in the non-Faradaic regions. The comparison of the SERS signals obtained in several redox states, and at several excitation wavelengths, allows the evolution of the electromagnetic, resonance Raman and charge-transfer mechanisms at the electrode surface.