Why It Is About to Get a Lot More Difficult to Produce Counterfeit Cash

A team of scientists led by Jon Kellar at the South Dakota School of Mines and Technology have come up with a special QR code—using nanoparticles combined with blue and green fluorescent ink—that can be used to prevent counterfeiters from getting away with passing along forged cash.

The code is designed with standard computer-aided design (CAD) equipment and can be sprayed onto surfaces such as paper, plastic film, tape and glass, using an aerosol jet printer, reports the AFP.

The code is invisible until illuminated under a near-infrared laser.


The nanoparticles absorb photons at a non-visible wavelength but emit them in a visible wavelength, a trick called upconversion that causes the QR code to pop up almost like magic and allow itself to be scanned.

Already we see QR codes popping up (in black-and-white) on everything from Amtrak tickets to beer bottles to billboards; this nanoparticle technology represents a new advancement in the use and usefulness of such "quick response" scannable data.

"We have done significant wear tests, and all indications are that the ink is very durable," Kellar told AFP in an email exchange. [Google via Ubergizmo]


Image from Artist In Doing Nothing under Creative Commons license