Reversible photochromism and tunable luminescence switching in lanthanide-polyoxotungstate-agarose composite films

Stimuli-responsive materials integrating photochromism and luminescence switching are widely utilized in anticounterfeiting, data encryption, optical storage, green printing, and sensing. Here, a series of photoresponsive composite films with tunable multicolor luminescence were fabricated by doping lanthanide–polyoxotungstates into an agarose matrix via a combined sol–gel and casting method. Characterization via X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and elemental mapping confirmed the successful fabrication and uniform doping of the films. Spectroscopic analyses revealed that the dopant content effectively tuned the optical transmittance and emission intensity of the films. Crucially, the films exhibited reversible photochromism and synchronous luminescence switching upon alternating ultraviolet irradiation and oxygen exposure. This switching behavior was repeatable for a minimum of 10 cycles with minimal fatigue, underscoring their potential as multifunctional, stimuli-responsive smart optical materials.