NIT Rourkela builds lead-free material that glows blue, then switches off
By TUF News Desk · Published 28 October 2026 · 4 min read
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Heat it, and it glows blue under ultraviolet light. Let moisture back in, and the glow disappears. That reversible switch sits at the centre of a new material developed by researchers at the National Institute of Technology Rourkela, working with teams from the Indian Institute of Technology Guwahati, the Indian Institute of Technology Bombay and NISER Bhubaneswar.
The material is a bismuth-based organic-inorganic hybrid halide compound. It emits different colours of light when exposed to ultraviolet light, and it reacts to changes in heat and moisture. The findings have been published in the Journal of Materials Chemistry C, according to the announcement reported on October 28.
Why the team looked beyond lead
Many materials used to produce light contain lead. Lead-based photoluminescent materials are widely studied, but lead is toxic, which creates environmental and health problems. The Rourkela team went looking for a safer base, and settled on bismuth-based compounds, materials that combine organic and inorganic components and can produce useful light emission without lead.
The switching behaviour comes from water trapped inside the material’s structure. When the material is heated, it loses that trapped water, and it then emits blue light under ultraviolet light. When moisture returns, the material absorbs water again, and the blue light disappears. The process runs in reverse by changing the surrounding conditions.
Prof. Saroj L. Samal, associate professor in the Department of Chemistry at NIT Rourkela, said: “The Bi-based organic-inorganic hybrid halide compound is synthesized using cheaper and environmentally friendly constituents utilising a simple synthesis technique. The most interesting aspect of this material is its ability to undergo reversible structural transformation in response to heat and moisture, accompanied by change in its light emission properties.”
Samal worked on the study with research scholar Subhasish Sahoo. The wider team included Prof. Parameswar K. Iyer and Chakali Srinivas from IIT Guwahati, Rajanikanta Rana from IIT Bombay, and Prof. Himansu S. Biswal and Laxmipriya Dash from NISER Bhubaneswar.
Where it could be used
The most immediate use the team describes is protection against counterfeiting. Special inks containing the material could be printed on certificates and security labels. Their light-emitting properties could then be checked under ultraviolet light after controlled heating, as a way to verify whether an item is genuine.
Humidity sensing is another possibility. Because the material’s light emission changes with moisture, it could help monitor humidity in food packaging and storage facilities, places where moisture levels need to be controlled.
The team has also developed related lead-free LEDs that produce yellow light under ultraviolet light. Combining that yellow-light material with a commercially available blue-light material produced a white LED with a cool, daylight-like appearance. That white-light system kept stable emission during continuous operation, a positive sign for future lighting uses.
What comes next
The work is still at the laboratory stage. The team plans to explore ways to improve the material’s light-emission efficiency and long-term stability, and to study how it could be fitted into practical devices. Further studies will focus on anti-counterfeiting uses, on making sensors more sensitive and reliable, and on improving white LEDs.
For students, the study shows what research-led institutes work on beyond classrooms and placements. Students comparing research-led institutes can use our guide to choosing a university in India to weigh research output alongside courses and fees. Those interested in the institute itself can follow updates on the official NIT Rourkela website.
Frequently asked questions
What has the NIT Rourkela team developed?
A bismuth-based organic-inorganic hybrid halide compound that emits light under ultraviolet light and changes that emission when heated or exposed to moisture.
Why does lead-free matter here?
Lead-based light-emitting materials are widely studied, but lead is toxic and raises environmental and health concerns. The bismuth-based compound avoids lead entirely.
What could the material be used for?
The team points to anti-counterfeit inks for certificates and security labels, humidity sensors for food packaging and storage, and lead-free white LEDs.
Is the material ready for commercial use?
No. The team plans further work on light-emission efficiency, long-term stability and integration into practical devices before any commercial application.
Frequently asked questions
What has the NIT Rourkela team developed?
A bismuth-based organic-inorganic hybrid halide compound that emits light under ultraviolet light and changes that emission when heated or exposed to moisture.
Why does lead-free matter here?
Lead-based light-emitting materials are widely studied, but lead is toxic and raises environmental and health concerns. The bismuth-based compound avoids lead entirely.
What could the material be used for?
The team points to anti-counterfeit inks for certificates and security labels, humidity sensors for food packaging and storage, and lead-free white LEDs.
Is the material ready for commercial use?
No. The team plans further work on light-emission efficiency, long-term stability and integration into practical devices before any commercial application.
Sources: Biz Development News, Right Column Media