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Probing Plasmonic Effects on the Raman Activity of Ag Nanoparticle-Based Nanostructures through Terphenyl Diisocyanide Adsorption
journal contribution
posted on 2014-03-06, 00:00 authored by Giorgio Baraldi, Eduardo Lopez-Tobar, Kenji Hara, Santiago Sanchez-Cortes, José GonzaloNanostructures
consisting on Ag nanoparticle (NP) arrays produced by pulsed laser
deposition in vacuum and having different morphology are tested as
substrates for surface enhanced Raman spectroscopy (SERS) of terphenyl
diisocyanide (TPDI). The SERS response strongly depends on the NP
size and distribution; its intensity being much stronger in the case
of nanostructures containing small NPs with typical size in the range
of a few tens of nm and a characteristic interparticle spacing of
a few nm. This behavior is related to the existence of plasmonic hot
spots between these NPs upon excitation at wavelengths close to that
of their characteristic surface plasmon resonance, which favors the
Raman signal of TPDI molecules having both isocyanide groups attached
to Ag NPs. No changes in the spectral response are observed when the
concentration of the molecule varies in the range from 10–6 to 10–3 M, which suggests the saturation of the
available hot-spot sites at low concentrations. Finally, we investigate
the SERS response of covered nanostructures to prevent Ag tarnishing.
The SERS response decreases exponentially as the covering thickness
increases from 1 to 3 nm, which is related to the progressive reduction
of the uncovered Ag surface available to TPDI molecules.