Afterglow-Suppressed Lu₂O₃:Eu³⁺ Nanoscintillators for High-Resolution and Dynamic Digital Radiographic Imaging

Lu_2(1-Eu₂O₃ nanoscintillators (x = 0.005, 0.01, 0.03, 0.05, 0.07, and 0.10) with red emission were synthesized by a coprecipitation method. It is found that their photo- and radioluminescence intensities increase with increasing Eu³⁺ concentration until x = 0.05. According to their concentration-dependent luminescence intensity ratios (I₆₁₀(C₂)/I₅₈₂(S₆)), the existing energy transfer from Eu³⁺(S₆) (occupying S₆ sites) to Eu³⁺(C₂) (occupying C₂ sites) can be confirmed. Based on the spectral data and density functional theory (DFT) calculations, the origin of Lu₂O₃:Eu³⁺ persistent luminescence at low concentration might be related to the tunneling processes between Eu³⁺ (occupying C₂ and S₆ sites) and oxygen interstitials (O_i^×). After dispersing afterglow-suppressed Lu₂O₃:Eu³⁺ nanoscintillators into polymethyl methacrylate (PMMA) polymer-acetone solution, flexible PMMA-Lu₂O₃:Eu³⁺ composite films with high thermal stability and radiation resistance were fabricated by a doctor blade method. As the flexible composite film was used as an imaging plate, static X-ray images with high spatial resolution (5.5 lp/mm) under an extremely low dose of ∼1.1 μGy_air can be acquired. When a watch with a moving second hand was used as an object, the dynamic X-ray imaging can be realized under a dose rate of 55 μGy_air·s^-1. Our results demonstrate that Lu₂O₃:Eu³⁺ nanoscintillators can be regarded as candidate materials for dynamic digital radiographic imaging.