Scientists make 'programmable' luminescent markers

Researchers from Western University in Canada have developed luminescent markers that continue to glow after a UV light is removed and can be programmed to fade in stages, generating a signal that is very hard to copy by counterfeiters.

The new persistent luminescent (PersL) materials are inorganic phosphor nanoparticles that according to the team blend more easily with solvents than commercially available PersL, which have larger particle sizes, so are easier to apply and can be printed in very fine patterns.  

They glow given off is also much brighter and longer-lasting than current micrometre-sized PersLs and give off a shade of red light that’s not easily reproduced, according to a paper on the technology published in the journal ACS Applied Nano Materials. The material can also be tuned to determine how long it glows.

The materials were produced using the Canadian Light Source (CLS) synchrotron at the University of Saskatchewan, according to a statement on the discovery.

The researchers achieved the tuneability of the PersL nanoparticles by tinkering with the additives or "dopants" included in the base material, magnesium germanium oxide (MGO), to change its optical properties, according to CSL.

"Our ultimate goal is to find a material that is very difficult to clone…and use that as an anti-counterfeiting label," said Dr Lijia Liu, professor in the department of chemistry at Western University and one of the authors of the study.

"That is our ultimate security. It will be very difficult to find something that can achieve that property."