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.

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Photochromic materials have attracted broad interest to enhance the anti-counterfeiting of commercial products. In order to develop anti-counterfeiting mechanically reliable composite materials, it is urgent to improve the engineering process of both the material and matrix. Herein, we report on the development of anti-counterfeiting mechanically reliable nanocomposites composed of rare-earth doped aluminate strontium oxide phosphor (RESA) nanoparticles (NPs) immobilized into the thermoplastic polyurethane-based nanofibrous film successfully fabricated via the simple solution blowing spinning technology. The generated photochromic film exhibits an ultraviolet-stimulated anti-counterfeiting property. Different films of different emissive properties were generated using different total contents of RESA. Transmission electron microscopy was utilized to investigate the morphological properties of RESA NPs to display a particle diameter of 3–17 nm. The morphologies, compositions, optical transmittance, and mechanical performance of the produced photochromic nanofibrous films were investigated. Several analytical methods were employed, including energy-dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared spectrometry. The fibrous diameter of RESA-TPU was in the range of 200–250 nm. In order to ensure the development of transparent RESA-TPU film, RESA must be prepared in the nanosized form to allow better dispersion without agglomeration in the TPU matrix. The luminescent RESA-TPU film displayed an absorbance intensity at 367 nm and two emission intensities at 431 and 517 nm. The generated RESA-TPU films showed an enhanced hydrophobicity without negatively influencing their original appearance and mechanical properties. Upon irradiation with ultraviolet light, the transparent nanofibrous films displayed rapid and reversible photochromism to greenish-yellow without fatigue. The produced anti-counterfeiting films demonstrated stretchable, flexible, and translucent properties. As a simple sort of anti-counterfeiting substrates, the current novel photochromic film provides excellent anti-counterfeiting strength at low-cost as an efficient method to develop versatile materials with high mechanical strength to create an excellent market as well as adding economic and social values.

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