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Phys Chem Chem Phys. 2009 Sep 14;11(34):7437-43. doi: 10.1039/b903823j. Epub 2009 Jun 10.

Surface-enhanced Raman scattering of 5-fluorouracil adsorbed on silver nanostructures.

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1
CICECO, Chemistry Department, University of Aveiro, Aveiro, 3810-193, Portugal.

Abstract

Raman and surface-enhanced Raman scattering (SERS) of 5-fluorouracil (5-FU) have been recorded under several experimental conditions. SERS spectra have been analysed according to a resonant charge-transfer (CT) mechanism similar to a resonance Raman (RR) process, involving the photoinduced transfer of an electron from the Fermi level of the metal to vacant orbitals of the adsorbate (SERS-CT). In order to detect the enhancement mechanism and to identify the chemical species that give rise to the spectra, the theoretical SERS-CT intensities for the dienolic and diketo forms, and its respective N1 and N3 deprotonated anions (5-FU(-)), have been calculated and compared with the experimental results. In this way, the presence of N1 deprotonated anion is confirmed by SERS given that the calculated SERS-CT intensities predict the selective enhancement of the band at ca. 1680 cm(-1) in agreement with the experiment. Therefore, the metal-to-adsorbate CT process involves the transient formation of the respective radical dianion (5-FU (2-)), which is new evidence of the relevance of the CT enhancement mechanism in SERS.

PMID:
19690716
DOI:
10.1039/b903823j
[Indexed for MEDLINE]
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