Is the donor-acceptor electronegativity a good indicator for the surface enhanced Raman scattering (SERS)?

摘要

In this work, we study the interaction of neutral and ionic forms of Ag_8 and Au_8 with glycine to investigate the role of these interactions in the chemical enhancement (CE) component of the surface enhanced Raman scattering (SERS) effect. It is widely accepted that the charge transfer between metallic nanostructures and molecular species is a key issue in the underlying CE mechanism; consequently under this framework, and supported by the density functional theory, we introduce two recently described parameters, donor (π~-) and acceptor (π~+) electronegativity as useful concepts for the prediction of the charge transfer process and the concomitant CE effect. From this work, it could be inferred that the minimum binding energy (BE) necessary for the CE to take place averages 30 kcal/mol. For the systems we present here, CE is more intense when BE is more negative and this occurs when there is a substantial charge transfer. Thus, as π~- and π~+ represent good parameters for analyzing the charge transfer process, they are also good indicators of the contribution of CE to the SERS effect.