Coffee grounds yield covert anti-counterfeit marker

Researchers in South Korea have come up with a way to make anticounterfeit fluorescent materials from an unlikely source – used coffee grounds.

The team from Pukyong National University and Dong Eui Institute of Technology in Busan say they have developed a method to harvest fluorescent carbon dots that combines a higher yield, lower cost, and greater stability to factors like light bleaching than some much pricier rival technologies.

Interest in carbon dot nanoparticles as an anticounterfeit technology has risen sharply in the last few years, thanks in part to their bright fluorescence and non-toxic nature, and they have already started to feature in other applications like biomedical imaging.

Using an abundant raw material like coffee grounds to make carbon dots could help keep cost of production as low as possible, while also providing a new way to recycle the vast amount of grounds generated around the world each year.

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At the moment, this material is generally used for as a medium of mushrooms production, nutrient of earthworms for vermicompost, carbon source of activated carbon, ethanol and biogas, according to the researchers, who have published their work in the journal Optik.

They used hydrothermal synthesis to create the carbon dots, and dispersed them in a carrier to create a transparent ink that was applied as a covert feature in a mesh pattern on Korean banknotes for demonstration purposes.

The ink fluoresced with a blue colour when excited by ultraviolet light, but was invisible to the naked eye in regular daylight conditions.

“These attractive features can motivate the green and sustainable synthesis of fluorescent [carbon dots] in…anti-counterfeiting applications,” conclude the authors.

Photo by Mae Mu on Unsplash