Other applications could span medical imaging, optical sensing and glowing paints. They suggest that this could have use in the identification and anti-counterfeiting protection of luxury textiles and handbags. In a demonstration for their new material, the scientists coated cotton threads with a dye using the material, and used them for luminescent embroidery. 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.”
“Most current phosphorescent materials are either toxic or difficult to prepare, so we wanted to develop a new material that overcome these limitations. “We’ve found that immobilising 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. “All lignin glows weakly, but most of the light energy is lost by vibration of movement of the lignin molecules, meaning it isn’t clearly visible to the naked eye,” said Professor Tony James from the University of Bath’s Centre for Sustainable Circular Technologies. Tweaking the cavity sizes within the polymer network and varying the drying times of the polymer allowed them to tune the duration of the glowing. This inspired the research team to mimic the phosphorescent properties by crosslinking lignin within a 3D polymer network they were able to cause it to glow visibly for around one second. It found that basswood (also known as American linden) naturally and weakly phosphoresces, releasing light for a few milliseconds, due to lignin being trapped within a 3D matrix of cellulose.
The new study investigated the natural RTP of lignin, a group of polymers that give wood its rigid structure. Unlike room-temperature phosphorescence (RTP), fluorescence stops immediately and stopping when the light source is switched off.
Visible fluorescence occurs when these materials absorb energy with a short wavelength, such as UV frequencies, and emit the energy as visible light. Fluorescent materials are found in nature, including in some jellyfish, corals and tree frogs.