Coupling Photonic Bandgap Engineering with Photochromism for Upconversion Luminescence Modulation

Abstract

Reversible and wavelength-selective luminescence modulation is essential for advanced optical encryption, anticounterfeiting, and adaptive photonic devices. However, conventional photochromism-induced luminescence regulation is usually governed by a reabsorption effect, leading to nonselective intensity modulation. Herein, PbWO4:Yb3+/Er3+ inverse opal photonic crystals were fabricated through a template-assisted stepwise infiltration strategy, in which W- and Pb-containing precursor sols were sequentially introduced to avoid precipitation and ensure the formation of ordered photonic architectures. The obtained PbWO4:Yb3+/Er3+ inverse opals exhibit tunable photonic stop-bands and distinct structural colors. By matching the photonic bandgap with Er3+ emission bands, wavelength-selective inhibition and band-edge-enhanced upconversion luminescence were achieved, enabling the regulation of the red-to-green emission ratio. X-ray-induced photochromism originates from the synergistic effect of oxygen vacancy-related color center formation and polaron hopping associated with W6+/W5+ mixed-valence states, providing a reversible route for overall emission intensity modulation. Benefiting from the structural-color masking effect and coloration-induced upconversion luminescence modulation, concealed information writing and 980 nm laser-readable optical patterns were demonstrated. This work provides an effective strategy for integrating photonic bandgap engineering with photochromism toward upconversion luminescence modulation and advanced optical anticounterfeiting applications.