Lanthanide(III)-Cu4I4 Organic Framework Scintillators Sensitized by Cluster-Based Antenna for High-Resolution X-ray Imaging

Scintillator-based X-ray imaging has attracted great attention from industrial quality inspection and security to medical diagnostics. Herein, a series of lanthanide(III)-Cu4I4 heterometallic organic frameworks (Ln-Cu4I4 MOFs)-based X-ray scintillators are developed by rationally assembling X-ray absorption centers ([Cu4I4] clusters) and luminescent chromophores (Ln(III) ions) in a specific manner. Under X-ray irradiation, the heavy inorganic units ([Cu4I4] clusters) absorb the X-ray energy to populate triplet excitons via halide-to-ligand charge transfer (XLCT) combined with the metal-to-ligand charge-transfer (MLCT) state (defined as the X/MLCT state), and then the X-3/MLCT excited state sensitizes Tb3+ for intense X-ray-excited luminescence via excitation energy transfer. The obtained Tb-Cu4I4 MOF scintillators exhibit high resistance to humidity and radiation, excellent linear response to X-ray dose rate, and high X-ray relative light yield of 29 379 +/- 3000 photons MeV-1. The relative light yield of Tb-Cu4I4 MOFs is approximate to 3 times higher than that of the control Tb(III) complex. X-ray imaging tests show that the Tb-Cu4I4 MOFs-based flexible scintillator film exhibits a high spatial resolution of 12.6 lp mm(-1). These findings not only provide a promising design strategy to develop lanthanide-MOF-based scintillators with excellent scintillation performance, but also exhibit high-resolution X-ray imaging for biological specimens and electronic chips.

Automated summary

Scintillator-based X-ray imaging has been developed using lanthanide(III)-Cu4I4 heterometallic organic frameworks (Ln-Cu4I4 MOFs) which consist of X-ray absorption centers ([Cu4I4] clusters) and luminescent chromophores (Ln(III) ions). The [Cu4I4] clusters absorb X-ray energy to generate triplet excitons through halide-to-ligand charge transfer (XLCT) and metal-to-ligand charge transfer (MLCT) state. These excitons excite Tb3+ to produce intense X-ray-excited luminescence through energy transfer. Tb-Cu4I4 MOFs exhibit high resistance to humidity and radiation, linear response to X-ray dose rate, and high X-ray relative light yield. X-ray imaging with Tb-Cu4I4 MOFs-based flexible scintillator film shows high spatial resolution.