Enhancement of photoluminescence, persistent luminescence and photocatalytic activity in ZnGa2O4 phosphors by lithium ion doping

• The phosphors ZnGa2O4 and Li0.15Zn0.85Ga2O4 were successfully synthesized by solid-state reaction method.
• The persistent luminescence of Li0.15Zn0.85Ga2O4 phosphor could be observed for 30 min by naked eyes.
• The persistent luminescence and photocatalytic performance of the (Li)ZnGa2O4 were measured.
• The role of lithium ion formed new cation vacancy.

The crystal structure, photoluminescence, persistent luminescence and photocatalytic properties of Li0.15Zn0.85Ga2O4 phosphors were investigated. X-ray diffraction (XRD) patterns indicated that Li-doped ZnGa2O4 had a spinel phase. The result of Raman spectra showed that the first order Raman active modes in spinel ZnGa2O4 were only attributed to Zn2+ ions in the tetrahedral sites. The Li+ ion doping into ZnGa2O4 led to enhancement of the emission intensity, and improved the persistent luminescence properties. When Li+ ion was incorporated into the ZnGa2O4 lattice, the new cation vacancy formed for the charge compensation and the cation vacancy would capture some of the excited electrons and acted as electron trap. Moreover, photocatalytic activity test shown that Li-doped ZnGa2O4 phosphor exhibited higher catalytic activities than the pure ZnGa2O4 for the degradation of Rhodamine B by the ultraviolet irradiation. It indicated that Li-doped ZnGa2O4 owned more traps to storage the photoinduced carriers, which decreased the combination of electrons and holes, resulting a higher catalytic activity.