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Issue 21, 2004
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Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach

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Abstract

The preparation of gold particle coated silica microspheres is described and the optical absorption spectra for various surface coverages of gold particles are presented. Onion-shell particles with the structure silica-gold-silica are also described. An effective medium model is used to quantify the surface plasmon shifts observed in such particles, which predicts the shifts in surface plasmon band for both solvent refractive index and surface coverage. The resultant microspheres exhibit absorption spectra resembling those of the isolated nanocrystals. However they possess extinction cross-sections orders of magnitude higher than the nanocrystals and can be centrifuged and redispersed more easily than the parent nanocrystals. The same effect can be obtained by coating silica spheres with gold nanorods, so that the plasmon absorption band can be tuned through the visible and NIR wavelength range. It is proposed that such micron-sized “nanoparticles” provide a practical means to amplify the unique optical properties of nanocrystals and make them more amenable to colloid processing.

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Article information


Submitted
06 Apr 2004
Accepted
29 Jul 2004
First published
26 Aug 2004

Phys. Chem. Chem. Phys., 2004,6, 5056-5060
Article type
Paper

Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach

I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán and P. Mulvaney, Phys. Chem. Chem. Phys., 2004, 6, 5056
DOI: 10.1039/B405157B

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