Color-tunable persistent luminescence phosphor for multimode dynamic anti-counterfeiting

Using a solid-state approach, the persistent luminescence property in sodium yttrium silicate which was single-doped or co-doped by europium or cerium was studied. The orthorhombic structure with the space group P212121 could be indexed to all samples, according to X-ray powder diffraction. The luminescence characteristics of these phosphors, including photoluminescence, luminescence degradation, and temperature-dependent emission, were systematically investigated. Under UV (∼365 nm) irradiation, blue/green emissions with broad bands peaking at 450/510 nm attributed to the characteristic 5d→4f/4f65d→4f7 transitions of Ce3+/Eu2+ could be observed in Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+, respectively. Moreover, blue and green persistent luminescence was also observed in Ce3+ or Eu2+ single-doped samples. Thermoluminescence curve of Na3LuSi3O9:Eu2+, Ce3+ reveals that Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+ have similar trap distribution. Tunable persistent luminescence can be realized via ratio control of Ce3+ and Eu2+. A possible afterglow mechanism was presented and discussed. The prepared materials have the potential of multimode dynamic luminescence, because they are highly sensitive to the composition, the excitation wavelength, and the detecting time. The outstanding abilities of Na3LuSi3O9:Ce3+, Eu2+ demonstrate the practical capability of this material for fingerprint identification and anti-counterfeiting.