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Researchers Develop New Tunable Anti-Counterfeiting Material

A person holds a magnifying glass up to a 100 dollar bill
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With counterfeiters getting ever more sneaky and competent in producing sophisticated fakes, there is a need to develop equally advanced anti-counterfeiting tech that can help verify anything from money and official documents, to artwork and medications.

To assist in the fight against counterfeit objects, researchers at Western University have developed a promising new technology that could make goods with identifying markers harder to forge. The new technology relies on a new type of persistent luminescence (PersL) nanomaterial that has been fabricated by the researchers. Their study has been published in ACS Applied Nano Materials.

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PersL materials offer new breakthrough in luminescent markers

In many countries, it is commonplace to include special markers on money, passports and other documents that only show up under ultraviolet (UV) light. This way, if an item is suspected of being counterfeit, a worker or agent can easily examine it using a UV light source and rapidly verify if it contains the expected UV-responsive marker strip.

While this technique worked well for years, over time forgers have been able to identify and exploit its weaknesses, leading to a renewed need for novel anti-counterfeiting measures.

PersL materials are a notable candidate for anti-counterfeiting technology. PersL materials are inorganic phosphor nanoparticles that glow a specific shade of red when exposed to UV light. Unlike traditional UV-responsive anti-counterfeiting materials, which glow under UV light but immediately switch “off” when that light is removed, PersL materials continue to glow for many seconds after initial exposure.

Ideally, scientists would be able to synthesize nanosized PersL particles that could be easily blended with solvent for printing advanced anti-counterfeiting patterns onto important documents. This longer glow time would be harder for forgers to replicate, thus improving security.

However, to date, the only reported method for creating suitable nanosized PersL materials comes with some significant drawbacks – it creates a very wide range of different particle sizes and suffers from severe problems with particle aggregation.

In their new work, the Western University researchers have been able to successfully synthesize PersL nanorods made from manganese-doped magnesium germanate (Mn-doped MgGeO3 or MGO:Mn). Their synthesis results in more uniformly distributed particle sizes, but it also results in nanorods with a more intense and longer-lasting PersL effect.

Tunable anti-counterfeiting measures for an extra layer of security

In addition to this long-lasting luminescence being difficult for a forger to replicate, the new MGO:Mn nanorods can also be “tuned” by doping them with different elemental additives during the synthesis process.

By adding co-dopants such as ytterbium, europium and/or lithium, the researchers could tweak the duration of the nanorods’ afterglow. Tuning the amount of these dopants, they were able to print patterns that faded at different rates.

“We can incorporate these into our material to construct a complicated pattern so that different parts glow for different durations,” said Lijia Liu, a professor in Western’s Department of Chemistry. “That is our ultimate security. It will be very difficult to find something that can achieve that property.”

Reference: Liu Y, Sun J, Jiang Y, et al. Multiband MgGeO3-based persistent luminescent nanophosphors for dynamic and multimodal anticounterfeiting. ACS Appl Nano Mater. 2024;7(10):11541-11552. doi: 10.1021/acsanm.4c01069

This article is a rework of a press release issued by the Canadian Light Source. Material has been edited for length and content.