Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 19: Poster 2: Biomolecules, Cold Molecules, Experimental Techniques, Various Topics

MO 19.26: Poster

Wednesday, March 20, 2013, 16:00–18:30, Empore Lichthof

Use of a Kretschmann Configuration for the Detection of Raman Spectra from Low-Concentration Aqueous Samples — •Alireza Mazaheri Tehrani, Faezeh Mohaghegh, and Arnulf Materny — Research Center for Functional Materials and Nanomolecular Science, Jacobs University, Campus Ring 1, D-28759 Bremen, Germany

In the Kretschmann configuration, surface plasmon polaritons (SPP) can be excited in a thin layer of coinage metals covering a prism surface when a specific angle of incidence is chosen for a light beam undergoing total internal reflection from this surface. The enhanced evanescent field then results in an increase of Raman scattering from molecules adsorbed to the metal surface. This surface-enhanced Raman scattering (SERS) technique usually works only within a very narrow angle range and yields orders of magnitude signal enhancement. In our work we were interested to utilize this technique to obtain Raman spectra from very small amounts of molecules (few µMol concentration). For our studies we have used a sapphire hemispherical prism (n ≈ 1.7) coated with a thin layer (≈ 45 nm) of silver. We show that sharp resonances occur under well-defined angles of incidence of the excitation beam yielding high detection sensitivity. However, when liquids are in contact with the metal layer surface, the angle range, under which SPP resonances can be obtained, is broadened compared to dried samples. This results in a reduced efficiency also for SERS.