US Patent 7682523 - CNT security ink

http://www.freepatentsonline.com/7682523.html

This patent from Rice University teaches an anti-counterfeiting ink using carbon nanotubes as a key ingredient. Claim 1 reads:

1. A fluorescent ink, comprising:

a solvent;

a surfactant; and

carbon nanotubes suspended in the solvent;

wherein the carbon nanotubes are dispersed in the solvent;

wherein the carbon nanotubes are fluorescent and have diameters of less than about 3 nm; and

wherein the carbon nanotubes have a visible excitation and an emission following the visible excitation; and

wherein the fluorescent ink is suitable for deposition on a surface.