UV-shielding photochromic composite films based on nanocrystalline cellulose modified with CeO₂ and WO₃ nanoparticles

The UV-shielding composite films based on nanocrystalline cellulose (CNC) modified with both CeO₂ and WO₃ nanoparticles were prepared by solvent casting method. In the composites, both CeO₂ and WO₃ nanoparticles showed redox activity under UV-irradiation, and the joint effects of that metal oxides in the composite films were evidenced. The WO₃ nanoparticles provided reversible photochromic properties to the WO₃/CNC film under UV-irradiation while CeO₂ nanoparticles inhibited the photochromic effect. The mechanism of this inhibition in the CeO₂/WO₃/CNC films was investigated using UV-vis and FTIR spectroscopy. The photodegradation of CNC catalyzed by CeO₂ nanoparticles inherent in CeO₂/CNC films was prevented by the addition of WO₃ nanoparticles. The CeO₂/CNC and CeO₂/WO₃/CNC films exhibited strong UV-shielding property. The synthesized photostable UV-shielding CeO₂/WO₃/CNC films with photochromic property which can easily be tuned by the CeO₂ to WO₃ ratio can be useful for various applications, including protection of UV-sensitive dyes and production of UV-shielding packages.