US Patent 8105847 - Nano-sized optical fluorescence label

http://www.freepatentsonline.com/8105847.html

This patent from Georgia Tech Research Corporation has priority going back to 2003 and includes some basic claims to metal nanoparticle biological tags. Claim 1 reads:

1. A composition comprising a water-soluble fluorescent label comprising an encapsulated noble metal nanocluster,

wherein the noble metal nanocluster is about 0.1 nm to 2 nm in diameter without encapsulation, and wherein the fluorescent label exhibits an emission spectrum.