Guwahati : Researchers at Indian Institute of Technology Guwahati have developed an advanced light-emitting nanomaterial that could strengthen protection against fake currency, forged documents and counterfeit products through highly secure invisible markings that are difficult to duplicate.

The research team developed specialised perovskite nanocrystals capable of generating precise light patterns invisible to the naked eye and nearly impossible to reproduce using conventional printing or imaging technologies.

The study was conducted by Saikat Bhaumik and P. K. Giri from the Department of Physics at IIT Guwahati, along with research scholars Latika Juneja and Garima Choudhary. The findings were published in the international journal Advanced Optical Materials.

Researchers said the innovation addresses the growing global challenge of counterfeiting, which affects industries including banking, pharmaceuticals, electronics, luxury goods and identity documentation.

Traditional anti-counterfeiting tools such as QR codes, holograms and watermarks are increasingly vulnerable to duplication using advanced imaging and printing technologies. To counter this, the IIT Guwahati team engineered nanocrystals that emit exceptionally pure and bright colours with unique optical signatures.

These nanocrystals, thousands of times smaller than a strand of human hair, can be used to create concealed security patterns for authentication purposes.

One of the major limitations of such materials has been their instability when exposed to heat, moisture and chemicals. The researchers addressed this issue by designing a special double-layer protective coating that preserves both the stability and luminescent properties of the nanocrystals.

Using a direct laser-writing technique, the team created microscopic security patterns without relying on conventional printing masks, enabling the production of highly detailed structures capable of storing hidden information.

Explaining the technology, Bhaumik said the material behaves differently from conventional security labels.

“Unlike normal labels that always show the same mark, these materials react differently to heat and chemicals. An invisible fluorescent pattern can disappear when heated and reappear after chemical treatment,” he said.

Researchers said the feature adds an additional layer of security, as counterfeiters would need to replicate not only the visible pattern but also the material’s specific response to environmental conditions. The team has termed the concept “4D anti-counterfeiting”.

Apart from security applications, the technology could also contribute to the development of next-generation micro-LED displays for smartphones, wearable devices and augmented reality systems.

The researchers said the material may eventually find applications in currency notes, passports, identity cards, branded products and luxury goods for advanced authentication and secure information storage.

However, they noted that the technology is currently at the laboratory stage and will require further testing and validation before commercial deployment.