Coating Red Phosphor on Green Luminescent Material for Multi-Mode Luminescence and Advanced Anti-Counterfeit Applications

Traditional fluorescent anti-counterfeiting materials usually exhibit fixed-wavelength excitation patterns and monochromatic luminescence, which are extremely easy to be counterfeited and have low security. Therefore, there is an urgent need to develop multi-mode fluorescent materials with enhanced security to address this issue. Here, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ core-shell structured phosphors were prepared via a sol-gel method. Coating SrAl2O4:Eu,Dy with Y2O3:Eu3+ red phosphor did not significantly change the crystal structure of SrAl2O4. Under UV excitation at 254 nm, SrAl2O4:1%Eu,2%Dy@Y2O3:Eu3+ exhibited red emission at 613 nm (5D0→7F2 transition of Eu3+), and a strong green afterglow was observed after removing the UV irradiation. However, blue-green emission at 496 nm was observed under UV excitation at 365 nm, followed by green afterglow upon removal of the light source. Varying the content of the Y2O3:Eu3+ shell yielded different emissions and afterglows. The prepared samples are sensitive to the excitation wavelength and duration and have multimodal luminescence properties, which can be used for anti-counterfeiting patterns. The outcomes in this work indicate that the phosphor is a promising fluorescent material for anti-counterfeiting.