Impact of the plasmonic near- and far-field resonance-energy shift on the enhancement of infrared vibrational signals

We report on the impact of the differing spectral near- and far-field properties of resonantly excited gold nanoantennas on the vibrational signal enhancement in surface-enhanced infrared absorption (SEIRA). The knowledge on both spectral characteristics is of considerable importance for the optimiz...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2015-09, Vol.17 (33), p.21169-21175
Main Authors: Vogt, Jochen, Huck, Christian, Neubrech, Frank, Toma, Andrea, Gerbert, David, Pucci, Annemarie
Format: Article
Language:English
Subjects:
Excitation spectra
Gold
Infrared
Infrared absorption
Nanostructure
Plasmonics
Spectra
Spectroscopy
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Summary:We report on the impact of the differing spectral near- and far-field properties of resonantly excited gold nanoantennas on the vibrational signal enhancement in surface-enhanced infrared absorption (SEIRA). The knowledge on both spectral characteristics is of considerable importance for the optimization of plasmonic nanostructures for surface-enhanced spectroscopy techniques. From infrared micro-spectroscopic measurements, we simultaneously obtain spectral information on the plasmonic far-field response and, via SEIRA spectroscopy of a test molecule, on the near-field enhancement. The molecular test layer of 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) was deposited on the surface of gold nanoantennas with different lengths and thus different far-field resonance energies. We carefully studied the Fano-type vibrational lines in a broad spectral window, in particular, how the various vibrational signals are enhanced in relation to the ratio of the far-field plasmonic resonance and the molecular vibrational frequencies. As a detailed experimental proof of former simulation studies, we show the clearly red-shifted maximum SEIRA enhancement compared to the far-field resonance.
ISSN:1463-9076
1463-9084
DOI:10.1039/c4cp04851b