Organic doping-based optimization of triplet radioluminescence of Tb3+/Ga3+ metallacrown scintillators for X-Ray detection

Triplet excitons serve as a critical pathway for harvesting energy released during X-ray interactions with heavy elements; however, strategies to enhance their activation efficiency remain limited. Herein, we report a novel organic doping approach to optimize the triplet radioluminescence (RL) of Tb 3+ /Ga 3+ metallacrown (Tb-1) scintillators. By introducing 1,2,4,5-benzenetetracarboxylic acid (PMA) as a ligand dopant, a new scintillation crystal, Tb-1-PMA, is synthesized. Compared to the Tb-1 crystal, Tb-1-PMA exhibits a significant reduction in metal content while maintaining structural integrity. When excited by ultraviolet light or X-rays, Tb-1-PMA crystal emit bright green light, and the photoluminescence quantum yield (PLQY) is increased from 36.8 % to 45.3 %. The RL intensity of Tb-1-PMA surpasses that of Tb-1 by 50 %, achieving a relative light yield of 17,000 photons MeV −1 , accompanied by nearly eliminated afterglow. These enhancements stem from improved energy-level alignment between organic triplet excitons and Tb 3+ in Tb-1-PMA, enabling efficient energy transfer. The RL intensity demonstrates a linear response to X-ray dose rates, with a detection limit of 0.044 μGy s −1 , approximately 123-fold lower than conventional diagnostic doses. This work provides a cost-effective and scalable strategy for designing organic-doped high-performance triplet-emitting scintillators.