Teak leaf extract offers a low-cost bio-degradable shield against lasers

An extract from teak leaf could offer a natural, biodegradable shield against lasers and help protect the human body as well as optical sensors against accidental exposure to high intensity electromagnetic rays in fields ranging from medical devises to military equipment.

Traditional optical shields rely on expensive synthetic materials such as graphene, fullerenes and metal nanoparticles, which can be harmful to the environment due to their technical methods of synthesis. In comparison, teak leaf extract is simple to obtain from nature and therefore provides a low-cost, sustainable solution.

While teak leaves are usually agricultural waste, they are rich source of anthocyanins, a type of natural pigments that give them a reddish-brown hue when extracted using suitable solvents.

Scientists at the Raman Research Institute (RRI), under the aegis of the Department of Science and Technology have uncovered an extraordinary property called nonlinear optical (NLO) in these pigments when they interact with light. This property of the dye makes the teak leaf a suitable candidate for optical power-limiting applications.

“Recognising this, we aimed to explore the potential of teak leaf extract as a non-toxic, biodegradable, eco-friendly and economically viable alternative to synthetic dyes in the field of nonlinear optics. By utilising this underexploited natural resource, we not only contributed to value-added waste utilisation but also promoted the development of sustainable photonic materials with properties comparable to conventional synthetic counterparts,” said Beryl C, a scientist associated with the project at RRI. The discovery has been published in the Journal of Photochemistry and Photobiology A: Chemistry, an American peer reviewed publication.

To harness the optical potential of teak leaves, the RRI team dried and powdered the leaves, soaked the powder in solvents and purified the extract through ultrasonication and centrifugation.

They were able to extract a vibrant, reddish-brown liquid dye and then shot green laser light through it at two levels of power: one steady and the other pulsing. The dye absorbed the light and adapted to it.

Through sophisticated experiments, the researchers found that the dye also showed reverse saturable absorption (RSA). This means the more intense the light, the more the dye absorbed, which is exactly the behaviour needed for laser safety gear.

“The discovery of natural, eco-friendly optical materials which are inexpensive, compostable and biodegradable is of very high importance regarding the future demands of photonic technologies,” the Ministry of Science and Technology said on Wednesday.

“This research opens up new possibilities for the manufacture of modern, eco-friendly laser protective equipment, such as safety goggles, shields for optical sensors and laser-resistant coatings, making use of the natural teak leaf extract,” the Ministry added. Future studies could focus on ways to make the dye more stable for long-term use and utilise it in commercial photonic devices.