• • Radioluminescence enhancements exceeding three orders of magnitude (1000-fold) over EuCl3 were achieved with Eu(NTA)3DPEPO, directly addressing the weak X-ray absorption and inefficient triplet utilization that plague organic scintillators, enabling high-sensitivity medical imaging and environmental monitoring.
• • Near-unity energy transfer efficiency (>99%) via Dexter-mediated triplet exciton recycling in f-f systems (Eu3+) was realized by aligning ligand triplet energy (19,600 cm−1 for NTA) slightly above the Eu3+ 5D0 level (17,200 cm−1), suppressing back-transfer and yielding 100-fold RL enhancement over EuCl3—critical for reducing radiation dose in clinical diagnostics.
• • d-f systems (Ce3+, Eu2+) exhibit high PLQY (~100%) but limited X-ray sensitivity due to narrow ligand absorption (<250 nm) and ultrafast decay (50 ns), resulting in lower RL intensity for Ce(Tp)3 compared to f-f systems, demonstrating that high PLQY does not guarantee high scintillation efficiency and redirecting material design toward triplet harvesting.
• • Coordination saturation with neutral Lewis bases (DPEPO, PHEN) optimizes exciton confinement, boosting RL intensity by an additional order of magnitude (from 100-fold to 1000-fold over EuCl3), providing a scalable molecular engineering route to replace toxic, costly inorganic scintillators in medical imaging and astronomy.