Near-Infrared Persistent Luminescence of CaTiO₃:Cr,Y for Imaging of Bone Implants Using Red-Light Illumination Instead of X-ray

Near-infrared (NIR) persistent luminescence (PersL) materials have unique optical properties with promising applications in bioimaging and anticounterfeiting. However, their development is currently hindered by poor red-light-exciting ability. In this study, CaTiO₃:Cr_0.001,Y_0.02 (CTCY) was synthesized with 650 nm-excited 772 nm NIR PersL. The Y³⁺ doping in the Ca²⁺ lattice plays a key role in the PersL property. A charge compensation mechanism was proposed, in which Cr³⁺ in the Ti⁴⁺ lattice was stabilized by Y³⁺-doping while oxygen vacancies were generated to store the excitation energy at the same time. A thermal ionization mechanism might elucidate the red-light-excited NIR PersL of CTCY, which benefits from the perovskite structure of CaTiO₃. CTCY has 120 times more intense red-light-excited PersL than Zn₃Ga₂Ge₂O₁₀:Cr. Its potential applications in luminescence anticounterfeiting and bioimaging were demonstrated using a visible/NIR dual-channel PersL flower painting and a CTCY-labeled bone screw for in situ reactivable PersL imaging using red light illumination instead of X-ray, respectively. This study not only provides a new NIR PersL material but also will add to our understanding in developing other potential red-light- or even NIR-activable PersL materials with perovskite-like structures.