States » EastPosted at: Oct 28 2026 4:19PM


NIT Rourkela scientists develop lead-free light-emitting materials for security, sensors

Bhubaneswar, Oct 28 (UNI) Scientists at the National Institute of Technology (NIT) Rourkela, in collaboration with researchers from IIT Guwahati, IIT Bombay and NISER Bhubaneswar, have developed lead-free light-emitting materials that respond to changes in temperature and moisture, opening up potential applications in anti-counterfeiting technology, humidity sensors and safer lighting systems.
The research focuses on bismuth-based organic-inorganic hybrid compounds that exhibit changes in their light-emission properties under ultraviolet (UV) exposure. The materials could offer an alternative to lead-based photoluminescent compounds, which are associated with environmental and health risks.
Published in the Journal of Materials Chemistry C, the study demonstrates that the developed bismuth-based material can reversibly switch its light-emission properties in response to changes in temperature and moisture.
When heated, the material releases water trapped within its structure and emits blue light under UV exposure. When exposed to moisture again, it absorbs water, causing the blue emission to disappear. This reversible response could be useful in applications that require optical signals to change under controlled environmental conditions.
The research paper was co-authored by Prof. Saroj L. Samal, Associate Professor in the Department of Chemistry at NIT Rourkela, and his research scholar Subhasish Sahoo. Other contributors include Prof. Parameswar K. Iyer and Chakali Srinivas of IIT Guwahati, Rajanikanta Rana of IIT Bombay, and Prof. Himansu S. Biswal and Laxmipriya Dash of NISER Bhubaneswar.
Explaining the significance of the development, Prof. Samal said the bismuth-based organic-inorganic hybrid halide compound was synthesised using relatively inexpensive and environmentally friendly constituents through a simple preparation 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,” he said.
The material could find applications in protecting important documents and commercial products against counterfeiting. Special inks incorporating the compound could potentially be used on certificates, signatures and security labels. Their authenticity could be verified by observing changes in light emission under UV exposure following controlled heating.
The material's moisture-responsive luminescence could also be explored for humidity-sensing applications in food packaging, storage facilities and other environments where monitoring moisture levels is essential.
In a related development, the NIT Rourkela research team has developed other lead-free light-emitting materials capable of producing yellow light under UV exposure. By combining the yellow-emitting material with a commercially available blue-light-emitting material, the researchers produced a white LED with a cool, daylight-like appearance.
The resulting lighting system maintained stable light emission during continuous operation, indicating potential for future applications in solid-state lighting and light-conversion technologies.
According to Prof. Samal, the synthesised compounds show promise for reversible luminescence switching, moisture sensing, solid-state lighting and anti-counterfeiting applications.
The researchers plan to improve the light-emission efficiency and long-term stability of the materials and explore their integration into practical devices. Future work will also focus on enhancing sensor sensitivity and reliability, developing advanced anti-counterfeiting technologies and optimising white-light-emitting diodes.
The findings could contribute to the development of responsive luminescent materials for optical security, environmental monitoring and potentially safer, cost-effective lighting technologies. However, further research and device-level testing will be necessary to establish their practical performance and suitability for commercial applications.
UNI DP
Tags: #NIT Rourkela scientists develop lead-free light-emitting materials for security# sensors
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