Achieving color-tunable luminescence in CaF2:Eu phosphors for multimode anti-counterfeiting

Abstract

Optical materials are widely used in the information coding, display, and anti-counterfeiting fields due to their tunable color. However, the regulation of the color change in a material is mainly achieved by co-doping with different ions to achieve multimode luminescence, which greatly increases the difficulty of material synthesis. Herein, CaF₂:Eu with different doping amounts of Eu ions as an anti-counterfeiting material is synthesized in one step by a simple high-temperature solid-state method. The concentration of Eu can adjust the reduction ratio of Eu ions and give the material multicolor emission. Moreover, X-ray-induced ion reduction achieves the multicolor emission of Eu²⁺ and Eu³⁺ ions in a single matrix of CaF₂:Eu. This achieves radio-photo luminescence (RPL). In addition, the mechano-luminescence (ML) of CaF₂: 0.5%Eu has also been confirmed. These findings provide unique insights into the design of highly integrated advanced anti-counterfeiting technologies using multi-stimuli-responsive luminescent materials.