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DS: Fachverband Dünne Schichten

DS 36: Vibrational Spectroscopy of Nanolayers with Optical Probes

DS 36.2: Invited Talk

Friday, February 29, 2008, 10:45–11:15, H 2013

Surface enhanced infrared spectroscopy — •Annemarie Pucci — Ruprecht-Karls-Universität Heidelberg, Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, 69120 Heidelberg

Surface enhanced infrared (IR) spectroscopy (SEIRS) is similar to surface enhanced Raman scattering (SERS) but its vibration signal enhancement is much less than that obtained with SERS; only up to three orders of magnitude in enhancement were achieved so far. The difference to SERS is based on the lower influence of local electromagnetic fields onto the signal enhancement. Electromagnetic field enhancement is the main enhancement effect in SEIRS and SERS and it is obtained with nano-structured metal films or with metal nanoparticles via plasmonic excitations of free electrons. Electromagnetic nearfield enhancement is strongest in nano-gaps and in proximity of sharp tips. Accordingly, metal particle systems close to percolation give a stronger effect in SEIRS of adsorbate vibrations than systems with lower or higher particle density. For single particles strong field enhancement in the IR can be obtained in case of a rod-like shape and a high aspect ratio. Such nanoantennas with length in the micrometer range behave similar to ideal antennas, which is qualitatively different to nanoparticles with resonances in the visible range. Exploiting the nearfield enhancement at the antenna resonance, SEIRS of molecules on the antenna allows extraordinary strong signal enhancement, which makes SEIRS to an interesting tool for medical and chemical sensing.