Scientists at the Institute of Nano Science and Technology (INST) have developed a groundbreaking luminescent ink with advanced security features to combat counterfeiting in currency, certificates, branded goods and medicines among a few others.

The INST is an autonomous Department of Science and Technology (DST) under the Union Science and Technology Ministry.

Counterfeiting is a growing problem worldwide and researchers are trying to find unique ways to prevent it. Luminescent properties of rare earth ions and the characteristic emissions of bismuth have long been known.

However, this is a first of its kind security ink based on luminescent nanomaterials with rare earth doping, enabling excitation dependent luminescence (Under both UV and NIR light it gives Visible emission).

By utilising rare earth ions and bismuth, this ink emits different colors under specific light wavelengths—vibrant blue, pink, and orange-red—making it difficult to duplicate, said a statement from the DST.

“Its unique properties allow for clear verification of authenticity in currency, certificates, medicines, and branded products.

This innovative solution promises to enhance product integrity and consumer trust, providing a powerful tool against counterfeiting.”

The ink can overcome the limitations of current covert tags, which are security features usually visible only under UV light and can be easily duplicated. “Specifically, the ink appears vibrant blue under 365 nm light, pink under 395 nm light, and orange-red under 980 nm near-infrared (NIR) light and remains effective under a range of light, temperature, and humidity conditions,” said the statement..

The luminescent nanomaterial was synthesised using a simple co-precipitation method at 120°C.

After synthesis, the nanomaterials were dispersed into commercially available PVC ink using sonication (process of dispersing nanoparticles into solvent by applying sound energy).

This mixture was then used to create patterns and letters through a screen-printing technique.

These printed patterns, when exposed to different wavelengths of light, clearly showed the desired colour changes, proving the effectiveness of the ink, said the statement.

By combining rare earth ions with well-known luminescent properties and bismuth with characteristic emissions, the team was able to enhance the encryption and decryption capabilities of the ink, improving its security potential.