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Smart windows with long-persistent phosphorescence, ultraviolet (UV) light protection, high transparency, and high rigidity were developed by easily immobilizing varying ratios of lanthanide-activated aluminate phosphor nanoscale particles within a composite of recycled polyester/cellulose nanocrystals (RPET/CNC). Cellulose nanocrystals were prepared from rice straw waste. Cellulose nanocrystals were used at low concentration as both crosslinker and drier to improve both transparency and hardness. The phosphor nanoscale particles must be distributed into the recycled polyester/cellulose nanocrystals composite bulk without agglomeration to produce transparent RPET/CNC substrates. Photoluminescence characteristics were also studied using spectroscopic profiles of excitation/emission and decay/lifetime. The hardness efficiency was also examined. This transparent recycled polyester waste/cellulose nanocrystals nanocomposite smart window has been shown to change colour under UV light to strong green and to greenish-yellow when it is dark, as proved by Commission Internationale de l'éclairage (CIE) laboratory colour parameters. It was found that the afterglow RPET/CNC smart window had phosphorescence intensities of 428, 493, and 523 nm upon excitation at 368 nm. There was evidence of improved UV shielding, photostability, and hydrophobic activity. In the presence of a low phosphor ratio, the luminescent RPET/CNC substrates showed quick and reversible fluorescence photochromic activity when exposed to UV radiation.

Several studies have been reported in order to utilize cellulosic based sorbents for lead decontamination from wastewater. However, the research still undergoes so that a highly efficient system is obtained. In the present study, cellulose nanocrystals (CNCs) were successfully decorated during the synthesis of silver (Ag) and zinc oxide (ZnO) nanoparticles, separately. The obtained nanocomposites, Ag/CNC and ZnO/CNC, have been intensively investigated with FTIR, XRD, XPS, and TEM to emphasize the workability of in-situ surface modification of CNCs with Ag and ZnO nanoparticles. The performance of these nanocomposites as effective adsorbents for lead ion Pb(II) has been evaluated under various conditions such as pH, temperature, concentration, and time. Generally, Ag/CNC nanocomposite improved Pb(II) uptake by ~ 22% while ZnO/CNC improved uptake by ~ 60% compared to CNCs. However, the results revealed that 60 min was sufficient time to reach adsorption equilibrium in all cases, which indicates a fast adsorption process. Moreover, ion uptake is enhanced by increasing pH, temperature, and concentration of Pb2+. The kinetic model is pseudo-second-order and the adsorption obeyed Langmuir isotherm (R2 ~ 0.997). The sorbents have revealed more than 94% removal efficiency for pb2+ from wastewater. Furthermore, the developed nanocomposites can be regenerated and reused for three cycles. No doubt, this work paves the way for next generation of functional biosorbants for water treatment applications.