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Proceedings Paper

SERS observed in periodic metallo-dielectric nanostructures fabricated using coated colloidal crystals
Author(s): Manuel R. Gonçalves; André Siegel; Othmar Marti
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Paper Abstract

Surface enhanced Raman scattering (SERS) has been investigated for different molecules adsorbed on metallic nanostructures. The local field enhancements due to the confinement and resonances of surface plasmons, can reach many orders of magnitude. These field enhancements allow molecules to produce strong Raman spectra, although they have tiny Raman scattering cross sections. The high sensitivity demonstrated was relevant for sensing applications of single molecules. We have investigated experimentally the SERS effect on rhodamine 6G molecules, adsorbed on triangular silver particles and photonic metallo-dielectric structures based on polymers. These structures were fabricated by evaporation of a thin metallic film on colloidal crystals followed by casting in PDMS and epoxy resin. In the later, the polystyrene spheres were removed by sonication in organic solvents. The remaining structure allows molecules to be adsorbed at its metallic surface, on top of the triangular particles or inside the spherical holes. The SERS spectra were measured by a scanning confocal Raman microscope. The location of the SERS active centers (hot spots) in arrays of triangular particles (corners and edges) is correlated with the optical near-field enhancements obtained by numerical simulations. In metallo-dielectric photonic structures made of PDMS the Raman images show regions of stable SERS spectra (several pixels wide) and many isolated bright pixels.The isolated pixels are instable in time, i.e. show spectral blinking. The photonic structures we propose can be fabricated in a reproducible way. The field enhancements depend mainly on the size and shape of the arrays, which is not the case for etched silver films and for clusters prepared by colloidal silver. Thus, they are more suitable to investigate the electromagnetic contribution to SERS.

Paper Details

Date Published: 23 April 2008
PDF: 12 pages
Proc. SPIE 6988, Nanophotonics II, 698809 (23 April 2008); doi: 10.1117/12.780561
Show Author Affiliations
Manuel R. Gonçalves, Ulm Univ. (Germany)
André Siegel, Ulm Univ. (Germany)
Othmar Marti, Ulm Univ. (Germany)

Published in SPIE Proceedings Vol. 6988:
Nanophotonics II
David L. Andrews; Jean-Michel Nunzi; Andreas Ostendorf, Editor(s)

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