Enhancing persistent luminescence and photocatalytic properties in Ti as a trap center in ZnGa₂O₄

ZnGa₂O₄ and ZnGa₂O₄:Ti phosphors were synthesized by the solid state method, and their persistent luminescence and photocatalytic properties were investigated in detail. The results of this study showed that Ti⁴⁺ doping improved the persistent luminescence properties. Thermoluminescence measurements demonstrated that the trap concentration considerably increased upon incorporation of Ti⁴⁺ ions into the ZnGa₂O₄ lattice. The traps generated by Ti doping were responsible for improvement in persistent luminescence. Furthermore, photocatalytic activity tests showed that the Ti-doped ZnGa₂O₄ phosphor exhibited much higher photocatalytic activity than the ZnGa₂O₄ host. UV–Vis diffuse reflectance spectra demonstrated that Ti-doped ZnGa₂O₄ shown a higher UV absorption efficiency. A comparison between the density of states of ZnGa₂O₄:Ti and ZnGa₂O₄ revealed that the bottom of the conduction band was modified by Ti doping. Hence, it could be concluded that Ti doping enhanced light harvest capability to generate more electron–hole pairs, and acted as a trap center by decreasing the recombination of photogenerated electrons and holes, resulting in the enhancement of both persistent luminescence and photocatalytic activity.