These materials respond to changes in temperature and humidity, and can be applied in security systems, sensors, and lighting technology.
Researchers from the National Institute of Technology Rourkela (NIT Rourkela), in collaboration with counterparts from the Indian Institute of Technology Guwahati (IIT Guwahati), the Indian Institute of Technology Bombay (IIT Bombay), and the National Institute of Science Education and Research Bhubaneswar (NISER Bhubaneswar), have developed a new material capable of emitting light in various colors when exposed to ultraviolet (UV) radiation.
These materials respond to changes in temperature and humidity, offering potential applications in security systems, sensors, and lighting technology.
The study explores bismuth-based compounds as a safer alternative to lead-based luminescent materials. While lead-based materials have been extensively researched for their light-emitting properties, they pose significant environmental and health risks due to the toxicity of lead.
Many materials currently used for luminescence contain lead, which is harmful to both human health and the environment. In search of safer alternatives, the researchers investigated bismuth-based compounds—a class of materials comprising both organic and inorganic components that can provide useful luminescent properties without the need for lead.
Associate Professor Saroj L. Samal noted, “The most intriguing aspect of this material is its ability to undergo reversible structural transformations in response to heat and moisture, which in turn alters its luminescent characteristics.”
This discovery holds promise for protecting important documents and products against counterfeiting. For instance, special inks incorporating this new material could be used for certificates, signatures, and security labels. Following controlled heating, the material’s luminescent properties can be observed under UV light, serving as a means to verify the authenticity of an item.
The material could also be utilized in humidity sensors. Since its luminescence intensity varies with humidity levels, it can be employed to monitor moisture in food packaging, storage facilities, and other environments where humidity control is essential.
Future research will focus on developing highly efficient, stimulus-responsive luminescent materials for anti-counterfeiting, enhancing the sensitivity and reliability of sensors, and optimizing the performance of white light-emitting diodes (LEDs). These efforts aim to translate these research findings into practical technologies for applications such as optical security, environmental monitoring, and cost-effective, energy-efficient lighting.