US Patent 7292334 - Enhanced Raman spectroscopy using plural nanoparticle types

http://www.freepatentsonline.com/7292334.html

This patent from Hewlett Packard finds a combination of metallic nanoparticles (Au, Ag, Cu) with inactive nanoparticles (colbolt, silica, alumina) has the effect of enhancing Raman spectroscopy. Claim 1 reads:

1. A two-dimensional array of nanoparticles usable for enhancing Raman scattered radiation in NERS comprising: a first plurality of nanoparticles; and a second plurality of nanoparticles of size and shape substantially similar to the size and shape of the first plurality of nanoparticles, the second plurality of nanoparticles exhibiting a plasmon frequency differing from any plasmon frequency exhibited by the first plurality of nanoparticles, the second plurality of nanoparticles being interspersed among the first plurality of nanoparticles in the two-dimensional array of nanoparticles.