Near-Infrared Persistent Luminescence of CaTiO: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, CaTiO:Cr,Y (CTCY) was synthesized with 650 nm-excited 772 nm NIR PersL. The Y doping in the Ca lattice plays a key role in the PersL property. A charge compensation mechanism was proposed, in which Cr in the Ti lattice was stabilized by Y-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 CaTiO. CTCY has 120 times more intense red-light-excited PersL than ZnGaGeO: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.