Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 53: Nanostructures at surfaces: Dots, particles, clusters III

O 53.12: Talk

Thursday, March 26, 2009, 17:45–18:00, SCH A215

Surface enhanced Raman scattering of polymer molecules — Manuel Gonçalves and •Othmar Marti — Universität Ulm - Inst. für Experimentelle Physik, Albert-Einstein-Allee 11, 89069 Ulm, Deutschland

Localized surface plasmons may enhanced the near-fields several orders of magnitude. The near-field enhancement depends strongly on shape and material of the metallic nanostructure. These enhancements permit to obtain Raman spectra of few of single molecules. However, spectral fluctuations and blinking were observed for single molecules adsorbed on metallic nanoparticles.

Surface enhanced Raman scattering (SERS) has been observed on polymer films, cast on silver nanostructures. Polymers as polybutadiene (PB), polybutadiene-block-polyisoprene (PB-b-PIP), poly(methyl methacrylate) (PMMA), and the elastomer polydimethylsiloxane (PDMS) were investigated. These materials present low fluorescence when illuminated with laser light of wavelength λ = 532 nm, comparing to dye-molecules as Rhodamine 6G, usually used in SERS measurements. On the other hand, polymer molecules have long chains and may have many orientations close to routh metal surface. Therefore, averaged SERS spectra are expected for films. Nevertheless, SERS spectra with spectral fluctuations and blinking were observed.

The highest Raman enhancements occur at the edges and corners of the metallic particles. The near-field enhancements obtained from FEM based calculations confirm the experimental observations.