US Patent 8226015 - Orthogonal charge-based spectral coding with quantum dots

http://www.freepatentsonline.com/8226015.html

This patent based on U.S. Naval research teaches a method of preparing nanocrystals for applications as biological tags so as to distinguish between concurrent cellular events. Claim 1 reads:

1. A method of preparing optical barcodes, comprising:

combining a plurality of populations of quantum dots with quantities of a modulator of photoluminescence to produce a plurality of optical barcodes,

wherein the plurality of optical barcodes have at least two distinguishable colors arising from varying quantities of a modulator of photoluminescence bound to the populations of quantum dots,

wherein the modulator of photoluminescence acts to quench or enhance photoluminescence.