Fig. 1. Emissions spectra and persistent luminescence curves of Zn_1+xGa_2－0.01－yGe_xO_3x+4∶0.01Cr, yBi (x=1, 2, 3, 4). (a) Emissions spectra; (b) persistent luminescence curves

Fig. 2. Emissions spectra and persistent luminescence curves of Zn₃Ga_1.99－yGe₂O₁₀∶0.01Cr, yBi with different Bi³⁺ contents. (a) Emissions spectra; (b) persistent luminescence curves

Fig. 3. Effect of reaction conditions on persistent properties of Zn_1+xGa_2－0.01－yGe_xO_3x+4∶0.01Cr, yBi. (a) Persistent luminescence curves with different thermal reaction time;(b) persistent luminescence curves with different thermal reaction temperatures; (c) persistent luminescence curves with different annealing temperatures

Fig. 4. XRD patterns. (a) XRD patterns of PLNPs with different Bi³⁺ doping contents; (b) XRD patterns of PLNPs with different annealing temperatures

Fig. 5. Excitation spectrum of Zn₃Ga_1.97Ge₂O₁₀∶0.01Cr, 0.02Bi

Fig. 6. Persistent luminescence spectra of Zn₃Ga_1.97Ge₂O₁₀∶0.01Cr, 0.02Bi. Inset: persistent luminescence pictures before irradiation (a), excited at 254 nm (b), 5 s after stop irradiation (c), and 15 s after stop irradiation (d) obtained by digital camera

Fig. 7. Afterglow image of Zn₃Ga_1.97Ge₂O₁₀∶0.01Cr,0.02Bi