Broadband near-infrared persistent luminescence in Ni2+-doped transparent glass-ceramic ZnGa2O4.

Transparent glass-ceramics are a highly attractive class of materials for photonic applications. Transition metal ions are promising candidates for luminescence centers thanks to the sensitivity of the ligand ions to d–d electron transition. Here, broadband second near-infrared (NIR-II) photoluminescence was achieved via precipitation of ZnGa₂O₄:Ni²⁺ nanocrystals within a zinc gallium–silicate glass matrix by a crystallization process. Excited by 260 nm UV photons, ZnGa₂O₄:Ni²⁺ GC displays NIR-II emission peaking at 1240 nm and has a full width at half maximum wider than 288 nm, attributed to ³T_2g(³F) → ³A_2g(³F) electronic transition of octahedrally coordinated Ni²⁺ ions. Moreover, broad persistent luminescence of Ni²⁺ ions can be effectively obtained after irradiation in UV light. Based on the electron paramagnetic resonance spectra and a thermoluminescence method, a physical model was constructed to demonstrate the mechanism of persistent luminescence. This developed afterglow luminescent glass-ceramic exhibits potential applications in biological imaging. [ABSTRACT FROM AUTHOR]