Shine-through luminescent wood membranes

Abstract

Thanks to its optical anisotropy and mechanical properties, luminescent wood is a promising material for indoor lighting applications. However, the state-of-the-art approaches make use of potentially toxic fluorophores and of non-biodegradable polymers to increase the transparency, compromising the otherwise excellent sustainability of wood. Moreover, these procedures require lengthy multistep functionalisation processes and often fail to preserve the natural aesthetics of wood. We took advantage of the intrinsically hierarchical structure of wood coupling it with an efficient fluorophore, europium dibenzoylmethide triethylammonium (EuD₃TEA), to achieve uniform illumination via a shine-through effect. A safe, low-power near-UV LED was used to excite the europium complex, and the light emitted was transmitted through the wood scaffold. We explored the effect of different wood cutting directions, as well as of lignin decolourisation. The optical transmission was the highest for cross-section cuts and could be further increased by decolourisation. Our approach is simple, sustainable and fully preserves the aesthetic appearance of natural wood. Moreover, thanks to the pH-responsiveness of EuD₃TEA photoluminescence, the resulting luminescent wood could be used as a sensor for acidic or alkaline vapours.