Scientists have developed a new type of glowing liquid that could help create harder-to-copy security markings for products, documents and other valuable items.
Researchers at Nottingham Trent University developed room-temperature liquids containing chemical elements that produce distinctive patterns of light.
They say the materials could provide a flexible new approach to optical tagging and anti-counterfeiting, while being compatible with existing processing and printing technologies.
The materials are a type of ionic liquid – salts that remain liquid at relatively low temperatures – combined with ‘lanthanide’ elements.
Lanthanides are a group of 15 metallic elements and several of which have distinctive light-emitting properties. When exposed to ultraviolet light, each produces its own characteristic pattern of wavelengths, giving the material a unique optical fingerprint.
The team developed four different glowing liquids – which can be easily mixed together – each containing one of the lanthanide elements.
Rather than having to develop and manufacture a completely new material for every security code, it would be possible to combine the different glowing liquids in different proportions.
As part of the study, the researchers demonstrated mixtures containing two different lanthanides, as well as more complex combinations containing three or four.
The mixtures produced increasingly complex light signatures, while retaining the characteristic emissions of the individual components.
This means that a relatively small number of basic materials can be combined to create a much larger range of optical signatures without requiring additional chemical synthesis.
Many security systems today rely on features that can be difficult to reproduce, such as specialised inks, holograms or other optical effects.
The researchers wanted to explore whether materials with complex light signatures could provide an additional layer of security.
A security marking made with one of the liquids could look ordinary under normal conditions but reveal a distinctive pattern when examined under ultraviolet light.
The team demonstrated the materials on paper, showing that different lanthanide liquids and mixtures produced different optical responses under ultraviolet light at different wavelengths.
The initial work has demonstrated the potential of the materials, although further research would be required to fully establish how they might perform in real-world applications.
“This could have potential applications in optical tagging and secure identification, including anti-counterfeiting technologies,” said senior author Dr Anthony Fitzpatrick, a researcher in Nottingham Trent University’s School of Science and Technology.
He said: “The materials could potentially be incorporated into printed security features or other systems where a distinctive optical response is used to verify that an item is genuine.
“Creating a more complex security signature does not require creating more complicated materials. Instead, different luminescent liquids can be combined to produce new signatures.
“That could make the approach easier to adapt for different applications, potentially allowing manufacturers to create tailored optical tags or identification systems without having to synthesise a new material for every application.”
Nottingham Trent University PhD student Annie Prasad added: “A key feature is that the new materials remain liquid at room temperature, making them easier to mix and formulate than materials that need to be processed as solid compounds. In addition to this, their properties could make them suitable for processing and printing technologies already used to produce security markings.”
The study, which also involved the University of Liverpool and the University of Manchester, is published in the Royal Society of Chemistry journal RSC Advances .
RSC Advances
Observational study
Not applicable
Room-temperature luminescent lanthanide ionic liquids for optical tagging and anti-counterfeiting
21-Sep-2026