A dynamic photochromic lanthanide film based on polyvinyl alcohol/chitosan for multi-level anti-counterfeiting and...

Recently, the development of new anti-counterfeiting materials with dynamic optical responses and additional functions has become a research hotspot, but the existing anti-counterfeiting materials often lack sufficient multifunctional integration. In this work, by using the water-soluble spiropyran derivative (SP-COOH) as a light-controlled switch and the terbium ion (Tb³⁺) sensitized by a bifunctional ligand (TPPBA) as the luminescent center, a multifunctional fluorescence anti-counterfeiting film (PVA-HACC-TPPBA-Tb-SP) based on polyvinyl alcohol (PVA) and quaternized chitosan (HACC) was designed and fabricated. The integration of each functional component in the film was achieved by covalent bonds, coordination bonds, and non-covalent interactions. Interestingly, the luminescence behavior of the film was excitation wavelength-dependent. Upon 365 nm UV irradiation, the film can realize the dynamic and reversible regulation of the luminescent color by photochromic reaction and energy transfer. However, under 254 nm excitation, the emission color was locked to stable green. Based on these characteristics, we successfully demonstrated the potential of the film in multi-level dynamic anti-counterfeiting applications, including rewritable patterning, time-dependent information hiding, and state-dependent optical encoding. Moreover, benefiting from the HACC, the film exhibited significant antibacterial activity against S. aureus and E. coli, which makes it resistant to microbial erosion in practical use. This study not only provides a new strategy for developing intelligent anti-counterfeiting materials, but also shows the broad application prospect of the integrated multifunctional film in high-end packaging, information security, and biomedicine.