Near-Infrared Persistent\nLuminescence of CaTiO<sub>3</sub>:Cr,Y for Imaging of Bone Implants\nUsing Red-Light Illumination\nInstead of X‑ray

Near-infrared (NIR) persistent luminescence (PersL) materials\nhave\nunique optical properties with promising applications in bioimaging\nand anticounterfeiting. However, their development is currently hindered\nby poor red-light-exciting ability. In this study, CaTiO<sub>3</sub>:Cr<sub>0.001</sub>,Y<sub>0.02</sub> (CTCY) was synthesized with\n650 nm-excited 772 nm NIR PersL. The Y<sup>3+</sup> doping in the\nCa<sup>2+</sup> lattice plays a key role in the PersL property. A\ncharge compensation mechanism was proposed, in which Cr<sup>3+</sup> in the Ti<sup>4+</sup> lattice was stabilized by Y<sup>3+</sup>-doping\nwhile oxygen vacancies were generated to store the excitation energy\nat the same time. A thermal ionization mechanism might elucidate the\nred-light-excited NIR PersL of CTCY, which benefits from the perovskite\nstructure of CaTiO<sub>3</sub>. CTCY has 120 times more intense red-light-excited\nPersL than Zn<sub>3</sub>Ga<sub>2</sub>Ge<sub>2</sub>O<sub>10</sub>:Cr. Its potential applications in luminescence anticounterfeiting\nand bioimaging were demonstrated using a visible/NIR dual-channel\nPersL flower painting and a CTCY-labeled bone screw for in situ reactivable\nPersL imaging using red light illumination instead of X-ray, respectively.\nThis study not only provides a new NIR PersL material but also will\nadd to our understanding in developing other potential red-light-\nor even NIR-activable PersL materials with perovskite-like structures.