Study of Adenine and Guanine Oxidation Mechanism by Surface-Enhanced Raman Spectroelectrochemistry

Metal nanoparticles are systems largely employed in surface-enhanced Raman spectroscopy (SERS). In particular, gold nanoparticles are one of the best substrates used in this field. In this work, the optimal conditions for gold nanoparticles electrodeposition on single-walled carbon nanotubes electrodes have been established to obtain the best SERS response. Using this substrate and analyzing the changes of in situ Raman spectra obtained at different potentials, we have been able to explain simultaneously the oxidation mechanism of purine bases, differentiating the oxidation intermediates and their orientation during the different oxidation steps. Adenine orientation hardly changes during the whole oxidation; the molecule maintains a parallel configuration and only shows a slightly tilted orientation after the first oxidation step. On the other hand, guanine orientation changes completely during its oxidation. Initially, guanine is perpendicular respect to gold nanoparticles, changing its orientation after the first oxidation process when the molecule shows a slightly tilted orientation, and it finishes parallel respect to the electrode surface after the second oxidation step.Junta de Castilla y Leon (GR71, BU349-U13) and Ministerio de Economia y Competitividad (CTQ2010-17127) is gratefully acknowledged. D.I. thanks Ministerio de Economia y Competitividad for his predoctoral FPI fellowship. A.S. and M.K. acknowledge the support from MSMT ERC-CZ project: LL1301.This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publishe