Silver coated latex spheres

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Abstract
Polystyrene (PS) and poly-methylmethacrylate (PMMA) particles have been coated with a silver shell from silver salt solutions by chemical reduction. The resulting colloidal particles exhibit absorption spectra which are red-shifted and broadened, as compared to the absorption of homogeneous silver particles of the same size. A simple self-consistent calculation of the polarization of a coated sphere is presented. The absorption spectrum and the enhanced optical field in the dielectric core of the particles are calculated. Enhanced Raman signals of the polystyrene material enclosed by the silver shell are observed; the measured intensities are compared with calculated enhancement factors.