Charge-transfer surface-enhanced resonance Raman spectra of benzene-like derivative compounds under the effect of an external electric field.

Since the discovery of surface-enhanced resonance Raman scattering (SERS), elucidating the charge-transfer (CT) mechanism has been a challenging and controversial process. Different theoretical models have been proposed to explain the effect of applied electrode potential on SERS-CT, but achieving a high-quality conserved trend of experimental observations and explaining the nature of the selective enhancement of the signals is not a trivial task and the results and conclusions are still in dispute. We investigated recently the performance of time-dependent excited-state gradient approximation under the effects of a uniform finite electric field in a simulation of the experimental spectra of pyridine on an Ag electrode.

Reply to the 'Comment on "Elucidation of charge-transfer SERS selection rules by considering the excited state properties and the role of electrode potential"' by M. Mohammadpour, M. H. Khodabandeh, L. Visscher and Z. Jamshidi, Phys. Chem. Chem. Phys., 2017, 19, 7833.

We appreciate Aranda's comments on our recent work entitled ''Elucidation of charge-transfer SERS selection rules by considering the excited state properties and the role of electrode potential''. We would also like to thank the editor of Physical Chemistry Chemical Physics for giving us an opportunity to specify more details of our work in this reply. An important part of our article concerns the role of the electrode potential in charge-transfer SERS spectra and we would like to first address the questions that Aranda et al.

Elucidation of charge-transfer SERS selection rules by considering the excited state properties and the role of electrode potential.

The goal of this study is to shed light on the charge-transfer (CT) mechanism of surface-enhanced Raman scattering (SERS) by considering the properties of CT excited states. The calculations have been done by means of an excited-state gradient approximation for a pyridine molecule interacting with a silver cluster, and provided a satisfactory improvement in comparison to previous work. The effect of electrode potential on the SERS-CT spectra has been modelled theoretically by applying an external electric field for selected CT transitions and the enhancement of the ν and ν modes and a decline in the intensity of the ν mode under a negative electric field (which is directed toward the cluster) have been observed.