Charge-transfer optical absorption mechanism of DNA:Ag-nanocluster complexes
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Universidade Federal de Minas Gerais
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Optical properties of DNA:Ag-nanoclusters complexes have been successfully applied experimentally in
Chemistry, Physics, and Biology. Nevertheless, the mechanisms behind their optical activity remain unresolved.
In this work, we present a time-dependent density functional study of optical absorption in DNA:Ag 4 . In all
23 different complexes investigated, we obtain new absorption peaks in the visible region that are not found
in either the isolated Ag 4 or isolated DNA base pairs. Absorption from red to green are predominantly of
charge-transfer character, from the Ag 4 to the DNA fragment, while absorption in the blue-violet range are
mostly associated to electronic transitions of a mixed character, involving either DNA-Ag 4 hybrid orbitals or
intracluster orbitals. We also investigate the role of exchange-correlation functionals in the calculated optical
spectra. Significant differences are observed between the calculations using the PBE functional (without exact
exchange) and the CAM-B3LYP functional (which partly includes exact exchange). Specifically, we observe a
tendency of charge-transfer excitations to involve purines bases, and the PBE spectra error is more pronounced
in the complexes where the Ag cluster is bound to the purines. Finally, our results also highlight the importance
of adding both the complementary base pair and the sugar-phosphate backbone in order to properly characterize
the absorption spectrum of DNA:Ag complexes.
Abstract
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Adsorção, DNA
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Adsorption, DNA
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https://journals.aps.org/pre/abstract/10.1103/PhysRevE.93.052413