Constructing Lanthanide-Organic Complexes for X-ray Scintillation and Imaging

The photoluminescent properties of lanthanide complexes have been thoroughly investigated; however, there have been much fewer studies showcasing their potential use in ionizing radiation detection. In this work, we delve into the photo- and radio-induced luminescence of a series of lanthanide-bearing organic-inorganic hybrids and their potential as a platform for X-ray scintillation and imaging. The judicious synergy between lanthanide cations and 2,6-di(1H-pyrazol-1-yl)isonicotinate (bppCOO⁻) ligands affords six new materials with three distinct structures. Notably, Eu-bppCOO-1 and Tb-bppCOO-2 display sharp fingerprint X-ray-excited luminescence (XEL), the intensities of which can be linearly correlated with the X-ray dose rates over a broad dynamic range (0.007–4.55 mGy s⁻¹). Moreover, the X-ray sensing efficacies of Eu-bppCOO-1 and Tb-bppCOO-2 were evaluated, showing that Tb-bppCOO-2 features a lower detection limit of 4.06 μGy s⁻¹ compared to 14.55 μGy s⁻¹ of Eu-bppCOO-1. Given the higher X-ray sensitivity and excellent radiation stability of Tb-bppCOO-2, we fabricated a flexible scintillator film for X-ray imaging by embedding finely ground Tb-bppCOO-2 in the polydimethylsiloxane (PDMS) polymer. The resulting scintillator film can be utilized for high-resolution X-ray imaging with a spatial resolution of approximately 7 lp mm⁻¹.