In each of these images, the left-hand leaf is embroidered with a fluorescent thread, while the two flowers are embroidered with the novel phosphorescent thread. Both threads glow under UV light (middle), but only the phosphorescent thread glows in the dark briefly (right). Image: Northeast Forestry University.
In each of these images, the left-hand leaf is embroidered with a fluorescent thread, while the two flowers are embroidered with the novel phosphorescent thread. Both threads glow under UV light (middle), but only the phosphorescent thread glows in the dark briefly (right). Image: Northeast Forestry University.

By harnessing the natural ability of wood to glow faintly, researchers have managed to develop a new sustainable phosphorescent material that could potentially be used for a wide range of applications, from medical imaging and optical sensing to ‘glow in the dark’ dyes and paints. The international team, led by researchers at the University of Bath in the UK and the Northeast Forestry University in China, investigated the natural phosphorescent properties of lignin, a major component of wood.

Room-temperature phosphorescence (RTP) happens when a material absorbs energy with a short wavelength (such as UV light) and then emits it as visible light. This contrasts with fluorescent materials, which immediately fluorescence when excited with light and stop glowing when the light is switched off.

The researchers found that basswood naturally and weakly phosphoresces, releasing light for a few milliseconds due to lignin being trapped within a 3D matrix of cellulose. This inspired them to mimic these glowing properties by crosslinking lignin within a 3D polymer network, causing it to glow visibly for around one second.

By tweaking the cavity sizes within the network and varying the drying times of the polymer, the researchers found they could alter the duration of the phosphorescence.

“All lignin glows weakly, but most of the light energy is lost by vibration or movement of the lignin molecules, meaning it isn’t clearly visible to the naked eye,” said Tony James, a professor at the University of Bath’s Centre for Sustainable Circular Technologies. “We’ve found that immobilizing the lignin in an acrylic polymer means more energy is emitted as light – in other words, the less it rattles about, the more it glows!

“Most current phosphorescent materials are either toxic or difficult to prepare, so we wanted to develop a new material that overcame these limitations. Although there is room for improvement, our new material shows great potential for making a more stable, sustainable, biodegradable non-toxic phosphorescent material that could be used in a range of applications.”

To test the new material, the team used it to dye threads. These phosphorescent threads could be used to produce luminescent textiles, for the easy identification and anti-counterfeiting protection of luxury textiles or bags.

“It is indeed an unexpected and interesting discovery,” said Zhijun Chen from the Engineering Research Center of Advanced Wooden Materials at Northeast Forestry University, who is lead corresponding author of a paper on this work in Cell Reports: Physical Science. “We think this work will not only provide a new option for sustainable afterglow materials but is also a new route for the value-added utilization of lignin, which is the main naturally occurring aromatic polymer, and the pulping industry produces 600 trillion tons per year.”

This story is adapted from material from the University of Bath, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.