A novel ink with enhanced security features developed with luminescent nanomaterials can help stop counterfeiting in currency, certificates, branded goods and medicines.

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.

Scientists at the Institute of Nano Science and Technology (INST), an autonomous institute of Department of Science and Technology, have used this property of rare earth materials, to synthesis 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).

Not only can the ink overcome the limitations of current covert tags, which are security features usually visible only under UV light and can be easily duplicated, it offers enhanced security features through its ability to display different colours under various light wavelengths. 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.

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

Made from these nanomaterials, it has significant potential to combat counterfeiting. It can be applied to fake-proof various items, including currency, certificates, medicines, and branded products. This allows both consumers and manufacturers to easily verify the authenticity of their items, providing a simple yet powerful tool to detect counterfeits.