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Science  28 Jan 2005:
Vol. 307, Issue 5709, pp. 483b
DOI: 10.1126/science.307.5709.483b

The Raman effect for measuring vibrational spectra is normally quite small, but in the vicinity of rough gold or silver surfaces, localized surface plasmons can enhance signals by orders of magnitude. However, variations in surface roughness can vary the enhancement of the surface enhanced Raman effect, or SERS, which makes it difficult to use for measuring concentrations. Jackson and Halas examined the SERS effect using core-shell nanoparticles of gold or silver nanoshell coatings over silica cores. Unlike colloidal metal particles, the core-shell particles exhibit SERS enhancements caused almost entirely by the plasmon resonances set up by their geometry, not from surface roughness or regions of high field caused by particle contact. The excitation frequency can be tuned to take full advantage of the plasmon response of the particles, which are simply deposited on glass slides. For a non- resonant excitation energy, the SERS enhancement for a typical organic molecule, p-mercaptoaniline, could be as high as 2.5 × 1010. — PDS

Proc. Natl. Acad. Sci. U.S.A. 101, 17930 (2004).

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