Heidelberg 2015 – scientific programme

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MO: Fachverband Molekülphysik

MO 16: Posters 3: Novelties in Molecular Physics

MO 16.23: Poster

Wednesday, March 25, 2015, 17:00–19:00, C/Foyer

Investigation of direct and indirect coupling of a adsorbate to the surface in SERS — •Faezeh Mohaghegh, Alireza Mazaheri Tehrani, and Arnulf Materny — Jacobs University, Campus Ring 1, 28759 Bremen, Germany

The surface enhancement of Raman Spectroscopy for molecules adsorbed to coin metal surfaces is still not completely understood. Surface-enhanced Raman scattering (SERS) was up to now mainly applied and studied using roughened metal films or metal nanoparticles as substrates. Unfortunately, these systems suffer from poor reproducibility. As an alternative, one could use flat metallic surfaces to achieve the better reproducibility, which is needed for fundamental research. However, due to phase matching conditions, the coupling of light to the surface plasmons in the metal is not straight forward. The most common setup to achieve this goal is called Kretschmann configuration. There, surface plasmon polaritons (SPPs) can be excited in a thin layer of a metal covering a prism surface when a specific angle of incidence is chosen for the internal reflection of a light beam, under which the phase matching condition is fulfilled. The enhanced evanescent field and the coupling of the electronic systems of metal and molecules then result in an increase of Raman scattering from molecules adsorbed to the metal surface. In our work, we present experimental results from Raman investigations using the Kretschmann arrangement. Specifically, we have investigated the direct and indirect coupling of adsorbate to the surface. In our fundamental study, dyes like Nile Blue are preferred, which are known for high SERS efficiency.