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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. April 2005, Volume 4, Number 4, 249-255 |
Adsorption Models of Bipyrazine on Silver Colloidal Nanoparticles: A Computational Study
Barbara Pergolese, Maurizio Muniz-Miranda, and Adriano Bigotto
Internet Electron. J. Mol. Des. 2005, 4, 249-255
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Abstract:
The Surface Enhanced Raman Scattering (SERS) spectra of
bipyrazine (BPZ) adsorbed on silver colloids display interesting
spectral features. In fact, upon addition of NaCl to the colloid,
some bands are split into doublets. This behavior can be explained
with two different interactions of BPZ with the silver surface. In
order to gain a better insight into the adsorption mechanism of
BPZ on silver, Density Functional Theory (DFT) calculations of
two models of the surface complexes of BPZ were performed. We
have performed DFT calculations using the B3LYP functional and
the LANL2DZ basis set. The B3LYP/LANL2DZ calculations of
two models of the surface complex of BPZ ("ortho" and "meta")
are able to account for the splitting of bands observed in the SERS
spectra. In fact, the components of the SERS doublets can be
assigned to normal modes of the two models of BPZ/Ag(I) surface
complex. The hypothesis of two different interactions of BPZ with
the silver surface is confirmed by the B3LYP/LANL2DZ
calculations of the two BPZ/Ag(I) models: a fraction of molecules
adsorbs on silver through the meta nitrogen atom and the
remaining part via the ortho nitrogen atom of BPZ. Thus, the
splitting of the SERS bands is ascribed to the presence of both
BPZ/Ag(I) complexes on the silver surface.
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