Red persistent luminescence in MgGa2O4 : Cr3+; a new phosphor for in vivo imaging

A new red-emitting long-lasting phosphorescence (LLP) material useful as biomarker for small animal in vivo imaging is presented. X-ray irradiated MgGa2O4 : Cr3+ is shown to be a suitable persistent phosphor emitting in the range 650–770 nm. In vivo re-excitation of its persistent luminescence is also possible with 580 nm excitation. MgGa2O4 : Cr3+ has almost 44% cationic site inversion. Cr3+ ion occupies octahedral site resulting in a broad emission peaking at 707 nm corresponding to Cr3+ 2E(2G) → 4A2(4F) transition. LLP is most intense for the compound with nominal Mg deficiency which also has the highest cation inversion. It is proposed that structural defects occurring due to cation inversion are responsible for LLP.