Designing Tb3+‐Sensitized Silica‐Nanoparticles‐Aided Eu3+‐Doped Sr2SiO4 Phosphors with Enhanced Luminescence for Anti‐Counterfeiting Applications

Silica‐nanoparticles‐assisted Eu3+‐doped Sr2SiO4 and Tb3+‐ and Eu3+‐co‐doped Sr2SiO4 phosphors, as potential phosphors for anti‐counterfeiting application are synthesized via a solid‐state reaction technique. The crystal structure, photoluminescence, and decay times are investigated. The characteristic emission of Eu3+‐doped Sr2SiO4 phosphors exhibits two major peaks at 617 and 595 nm under an excitation wavelength of 394 nm, which corresponds to 5D0 → 7F2 and 5D0 → 7F1 electron transitions of Eu3+ ions. Upon co‐doping with Tb3+, the red emission intensities of the Eu3+‐doped Sr2SiO4 phosphors are enhanced by 1.78‐fold times through an energy‐transfer process. The optimized Tb3+‐ and Eu3+‐co‐doped Sr2SiO4 phosphors show a decay time of 0.49 ns and an energy‐transfer efficiency of 73%. The calculated International Commission on Illumination value (x, y) and color purity are (0.63, 0.37) and 94%, respectively. Subsequently, a luminescent ink is formulated using the optimized phosphor and tested for efficiency on currency notes. Additionally, a flexible film is fabricated, and its luminescence properties are studied. The formulated ink can serve as security ink in the anti‐counterfeiting application.