“The research is an important step in utilizing natural wood for the development of functional wood materials”Ingo Burgert

Researchers at ETH Zürich and Scion in New Zealand have developed a bio-based, luminescent, water-resistant wood film that could lead to a range of uses in interior design, such as lighting systems and laminated cover panels, as well as in photonics and laser devices. The proposed luminescent wood is eco-friendly and made from renewable materials that could replace less environmentally friendly plastic-based products in optical lighting.

With growing interest in renewable materials and wood-based films for optical applications, many such materials are not sufficiently water resistant, exhibit poor mechanical properties, and require a petroleum-based polymer matrix. The team had initially explored making transparent wood materials, as this was more environmental friendly and did not depend on a polymer-matrix. Although this had been achieved in another study, the resulting transparent wood films were sensitive to moisture and possessed anisotropic light scattering. This pushed them to develop luminescent thin wood films with a hydrophobic coating and achieve isotropic light scattering for optical applications.

As reported in ACS Nano [Fu et al. ACS Nano (2020) DOI: 10.1021/acsnano.0c06110], balsa wood was treated with a solution that removed lignin and around half of its hemicelluloses, so that only a porous scaffold remained. The team then infused the delignified wood with a solution that contained quantum dots, semiconductor nanoparticles that glow in a specific color when bombarded with ultraviolet light. After compressing and drying, an hydrophobic coating was applied to produce a thick, water-resistant wood film with useful mechanical properties.

The resulting luminescent panel was tested by lighting up the inside of a toy house. Under UV light, the quantum dots in the wood emitted and scattered an orange light that distributed evenly across the surface of the film. On being exposed to UV light on the outside, a wood panel lights up an indoor space while a non-luminescent panel did not.

As lead author Ingo Burgert told Materials Today, “The luminescent transparent wood film combines an anisotropic structure and mechanical performance with an almost uniform luminescence due to isotropic light scattering”. In addition to the modification of the wood structure to allow an anisotropic cellulose scaffold with a hierarchical structure, different types of luminescent quantum dots could be embedded into the wood film to provide various colors of lighting products.

Burgert added “The research is an important step in utilizing natural wood for the development of functional wood materials”. The team now hope to work on producing the luminescent wood materials in an even more environmental friendly way.

Luminescent thin wood films with a hydrophobic coating
Luminescent thin wood films with a hydrophobic coating