On the chemical enhancement in SERS

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Abstract

In Surface-enhanced Raman scattering (SERS), the Raman signal of a molecule adsorbed on a metal surface is enhanced by many orders of magnitude. This provides a "finger-print" of molecules which can be used in ultrasensitive sensing devises. Here we present a time-dependent density functional theory (TDDFT) study of the molecule-surface chemical coupling in SERS. A systematic study of the chemical enhancement (CHEM) of meta-and para-substituted pyridines interacting with a small silver cluster (Ag 20) is presented. We find that the magnitude of chemical enhancement is governed to a large extent by the energy difference between the highest occupied energy level (HOMO) of the metal and the lowest unoccupied energy level (LUMO) of the molecule. A two-state approximation shows that the enhancement scales roughly as (ωXe)4, where ωe is an average excitation energy between the HOMO of the metal and the LUMO of the molecule and wX the HOMO-LUMO gap of the free molecule. Furthermore, we demonstrate that it is possible to control the CHEM enhancement by switching a dithienylethene photoswitch from its closed form to its open form. The open form of the photoswitch is found to be the strongest Raman scatterer when adsorbed on the surface whereas the opposite is found for the free molecule. This trend is explained using the simple two-state approximation.

Original languageEnglish (US)
Title of host publicationInternational Conference of Computational Methods in Sciences and Engineering 2009, ICCMSE 2009
Pages182-188
Number of pages7
DOIs
StatePublished - Dec 1 2012
EventInternational Conference of Computational Methods in Sciences and Engineering 2009, ICCMSE 2009 - Rhodes, Greece
Duration: Sep 29 2009Oct 4 2009

Publication series

NameAIP Conference Proceedings
Volume1504
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

OtherInternational Conference of Computational Methods in Sciences and Engineering 2009, ICCMSE 2009
CountryGreece
CityRhodes
Period9/29/0910/4/09

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All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Jensen, L. (2012). On the chemical enhancement in SERS. In International Conference of Computational Methods in Sciences and Engineering 2009, ICCMSE 2009 (pp. 182-188). (AIP Conference Proceedings; Vol. 1504). https://doi.org/10.1063/1.4771714