Infiltration of glass nanofiber-reinforced polylactic acid into delignified hardwood toward photoluminescent and mechanically reliable smart windows

Ultraviolet-protective, mechanically reliable, and photoresponsive wood that can switch color under ultraviolet light was developed. A combination of alkaline earth-doped strontium aluminate (ASA) as a photoluminescent pigment and glass nanofiber-supported polylactic acid as a hosting agent was infused into a delignified wood, producing transparent wood with photochromic activity. The ASA phosphor has proven high thermal stability and photostability. A typical process for producing colorless photoluminescent wood includes the well-dispersion of ASA in glass nanofiber-supported polylactic acid without agglomeration. As proven by the coloration measurements, the current photoluminescent wood becomes green under ultraviolet light and remains transparent under daylight. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) were employed to determine the morphology of the phosphor particles and glass fibers, demonstrating sizes of 12–21 nm and 50–125 nm, respectively. The luminescent wooden samples were studied by numerous microscopic and spectroscopic techniques, including SEM, X-ray fluorescence (XRF), and energy-dispersive X-ray (EDX). Upon excitation at 365 nm, the luminescence wood demonstrated an emission peak at 518 nm. When increasing the ASA concentration, the photoluminescent hardwoods displayed improved ultraviolet protection and better water resistance. The responsiveness of the luminescent wood to UV irradiation was fast and reversible.