Highly sensitive terbium-based metal–organic framework scintillators applied in flexible X-ray imaging†

Abstract

Scintillators have played an indispensable role in public security and medical diagnosis fields due to their ability to convert X-ray photons into visible light. Metal–organic frameworks (MOFs) have the advantages of designable structures, easy preparation of flexible films and high stability, and hence show great potential in the field of scintillation. However, research on flexible X-ray imaging based on MOF scintillators has been rather limited. The exploration and development of MOF-based flexible scintillation screens would be very promising and exciting. Here, a novel terbium-based MOF (Tb-MOF-1) scintillator was synthesized and employed for X-ray detection and imaging. Benefiting from the sensitizing effect of the ligand, Tb-MOF-1 shows excellent photoluminescence and radioluminescence signals, and its scintillation sensitivity is much higher than that of the commercial scintillator Bi₄Ge₃O₁₂ (BGO). Tb-MOF-1 shows a low X-ray detection limit of 1.71 μGy s⁻¹, which is lower than the demand for medical diagnosis of 5.5 μGy s⁻¹. The scintillation mechanism of Tb-MOF-1 is substantiated using spectroscopy and theoretical calculations. Furthermore, the robust structure of Tb-MOF-1 brings its strong tolerance against water and X-ray dosages, which facilitates its long-term operation. A flexible scintillation screen (Tb-MOF-screen) derived from Tb-MOF-1 was fabricated, achieving a high spatial resolution of 7.7 lp mm⁻¹@MTF 0.2. Ultimately, flexible X-ray imaging tests were successfully carried out by tightly fitting the Tb-MOF-screen to different curvature radii wires, which firstly verifies the X-ray imaging potential of Ln-MOF-based scintillation screens for non-planar objects.