Development of Photoluminescent Translucent Wood toward Photochromic Smart Window Applications

Photochromic transparent wooden materials are highly critical and attractive for smart windows, which have been scarcely investigated. In this context, we develop photochromic and fluorescent translucent wood with a color switching ability in the UV and visible spectrum regions, which is associated with color shifting properties. The fluorescent and photochromic translucent wood were generated by permeating a lignin-modified wooden substrate using a formulation containing methyl methacrylate (MMA) and a photoluminescent lanthanide-doped aluminum strontium oxide (SrAl2O4:Eu2+, Dy3+; ASOED) pigment characterized by good photo- and thermal stability. For a better preparation of photoluminescent transparent wood, the ASOED phosphor must be efficiently dispersed without aggregation in pre-polymerized MMA. This translucent wooden substrate demonstrated a color change from colorless in visible light to green under irradiation with UV as designated by CIE Lab colorimetric results. The morphological characteristics of the generated pigment nanoparticles (NPs) were studied using transmission electron microscopic micrographs. Scanning electron microscopy, elemental mapping, energy-dispersive X-ray spectroscopic analysis, wavelength-dispersive X-ray fluorescence spectroscopy, and hardness properties, in addition to UV-vis absorption and emission spectroscopy of the photochromic translucent wood samples, were used. The prepared photoluminescence transparent wood showed an absorption signal at 365 nm and two emission signals at 433 and 517 nm. The findings demonstrated that the generated transparent luminescent wood exhibited improved UV protection and superhydrophobic activity. The produced transparent luminescent wood showed fast and reversible photochromic responses to UV light without fatigue.