Mg doping induced enhancement of persistent luminescence of ZGGO: Cr3+ nanoparticles for time-gate optical encryption.

Herein, ZMGGO:Cr3+ nanoparticles were prepared by incorporating Mg2+ ions into Cr3+-doped zinc gallogermenate nanoparticles through a hydrothermal path in combination with a vacuum heating. The average size of ZMGGO:Cr3+ nanoparticles minishes from 59 to 12 nm with growing Mg2+ concentration. Meanwhile their luminescence intensity at 696 nm of ZMGGO:Cr3+ nanoparticles was only decreased by less than half of that of the undoped nanoparticles due to the decreased particle size after Mg doping. Meanwhile, the integral luminescence intensity of their entire emission band shows an increasing trend with increasing temperature due to the enhanced phonon sideband luminescence at high temperature. More important, it is found that the formation energies associated with Mg′ Ga -Gao Zn and Zn′ Ga -Gao Zn defects are −1.2 and 1.69 eV, respectively, suggesting the enhanced afterglow intensity of ZMGGO:Cr3+ can be ascribed to Mg doping leading to the increased number of these anti-site traps. Finally, the dual-level time-gate optical encryption was demonstrated using phosphorescent inks containing ZMGGO:Cr3+ nanoparticles with different afterglow intensities. • Mg2+ and Cr3+ codoped zinc gallogermanate (ZMGGO:Cr3+) nanoparticles were prepared. • Their average size decreases from 59 to 12 nm with increasing Mg concentration. • The presence of new anti-site traps improves their afterglow intensity. • The dual-level time-gate encryption was demonstrated using different afterglow inks. [ABSTRACT FROM AUTHOR]