Vibration assisted electron tunneling through nano-gaps in graphene nano-ribbons for amino-acids and peptide bond recognition

Peptide bond and amino-acid recognition by tunnel- ing current flowing across nano-gaps of graphene nano- ribbons has been recently discussed. Theoretical predictions of the tunneling current signals were approached in the elastic regime showing peculiar fingerprints. However, inelastic scattering due to vibrations are expected to play an important role. Then, the proposed strategy for peptide sequencing and amino-acid recognition is revised in the light of such inelastic scattering phenomena. Phonons and local vibrational modes assisted current tunneling is calculated by treating the electron-phonon scattering in the context of the lowest order expansion of the self-consistent Born approximation. We study the Gly and Ala homo- peptide cases as an example of very similar, small and neutral amino-acid that would be undistinguishable by means of standard techniques, such as the ionic blockade cur- rent, in real peptides. We show that all the inelastic contributions to the tunneling current are in the bias range 0V≤V≤0.5V and that they can be classified, from the atomistic point of view, in terms of energy sub-ranges they belong to. Peculiar fingerprints can be found for the typical configurations that have been recently found for pep- tide bonds recognition by tunneling current.