Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Plasmonics and Nanooptics
O 36.15: Poster
Dienstag, 17. März 2015, 18:15–21:00, Poster A
On the Importance of the Plasmonic Near-Field Spectrum for SEIRA — •Jochen Vogt1, Christian Huck1, Frank Neubrech1,2, Andrea Toma3, David Gerbert1, and Annemarie Pucci1 — 1Kirchhoff-Institute for Physics, Heidelberg University, Germany — 24th Physics Institute and Research Center SCoPE, University of Stuttgart, Germany — 3Istituto Italiano di Tecnologia, Genova, Italy
The near-field characteristics of plasmonic infrared (IR) nanoantennas are of great importance for molecular sensing, e.g., with surface-enhanced IR absorption (SEIRA). Recent studies investigated the spatial extend [1], lateral distribution, and Angstrom-scale surface-distance dependence [2]. In addition, the spectral near-field information is crucial to design optimum nanostructures for vibrational sensing. The red shift between the plasmonic near- and far-field intensity peaks that has to be considered in the design was theoretically described and then experimentally confirmed using scanning near-field optical microscopy [3] and, as shown in this contribution, by IR micro-spectroscopy. We investigated vibrational SEIRA signals of a thin molecular layer on IR nanoantenna substrates. Varying the spectral tuning of plasmonic resonance and molecular vibrations, we find the maximum SEIRA in accordance with the predicted near- and far-field resonance energy shift. Furthermore, depending on the detuning, we observe the enhanced vibrational signals as asymmetric lines that are described by the Fano model. [1] Neubrech et al., ACS Nano 2014 [2] Bochterle et al., ACS Nano 2012 [3] Alonso-Gonzalez et al., PRL 2013