US Patent 7041362 - Nanocrystal Bar Code

http://www.freepatentsonline.com/7041362.html

This one has been pending for a while (priority goes back to Nov 9, 1998) and apparently lays claim to nanocrystals (i.e. quantum dots) formed in a spatially arranged pattern for providing security (anti-counterfeiting) or verification code patterns. Claim 1 reads-

1. A method of providing a carrier material with an identifiable code pattern, the method comprising: applying an effective amount of one or more species of fluorescent water-soluble nanocrystals to the carrier material and operably linking the nanocrystals to the carrier material in an identifiable code pattern by linking reactive functionalities of the nanocrystal to the surface of the carrier material in a spatial arrangement, wherein the identifiable code pattern is used to determine the identity or authenticity of the carrier material.

Apparently the key differentiating factor from the prior art was that the code pattern was "in a spatial arrangement" as recited in all of the independent claims. The Examiner applied prior art that discussed the use of multiple quantum dots as tags for biological agents but, as argued by the attorney, the pliant nature of the biological cells would not allow spatially arranged deposits of water soluable quantum dots.