High‐Performance X‐Ray Imaging using Lanthanide Metal–Organic Frameworks

Abstract

Scintillating materials that convert ionizing radiation into low-energy photons hold great potential for radiation detection, nondestructive inspection, medical radiography, and space exploration. However, organic scintillators are characterized by low radioluminescence, while bulky inorganic scintillators are not suitable for the development of flexible detectors. Here, high-resolution X-ray imaging using solution-processable lanthanide-based metal-organic frameworks as microscale scintillators is demonstrated. Mechanistic studies suggest that lanthanide ions absorb X-rays to generate high-density molecular triplet excitons, and excited linkers subsequently sensitize lanthanide ions via nonradiative resonance energy transfer. Furthermore, the crystalline nature offers a delocalized electronic feature rather than isolated subunits, which enables direct trapping of charge carriers by lanthanide emitters. By controlling the concentration ratio between Tb 3+ and Eu 3+ ions, efficient and color-tunable radioluminescence of lanthanide ions can be achieved. When coupled with elastic, transparent polymer matrices, these metal-organic framework-based microscintillators allow the fabrication of flexible X-ray detectors. Such detectors feature a detection limit of 23 nGy s −1 , which is 240 times lower than the typical radiation dose for medical diagnosis. X-ray imaging with resolution higher than 16.6 line pairs per millimeter is further demonstrated. These findings provide insight into the future design of hybrid scintillators for optoelectronics and X-ray sensing and imaging.

Flexible strontium-based metal–organic framework scintillation screens for high-resolution X-ray imaging

“…Combined with the dramatically different RL intensities of 1 and the free ligand, the scintillation of 1 probably stems mainly from ligand-based electron transitions induced by the metal Sr 2+ absorption of X-ray photons. 8,20…”

“…7 Perovskites are considered as highly promising scintillators due to their high light yield, but their instability towards water and oxygen hinders their practical applications in X-ray detection and imaging. 8,9 Therefore, it is a great challenge and an urgent requirement to explore scintillators used to prepare flexible films with high performance, excellent stability and easy manufacture.…”

A 0D hybrid lead-free halide with near-unity photoluminescence quantum yield toward multifunctional optoelectronic applications

“…30,31 More significantly, some 0D hybrid metal halides have been further explored as X-ray scintillators with impressive light yield under X-ray excitation due to high PLQY and large Stokes shift. 32,33 For instance, 0D Mn 2+ and Cu + based halides display extraordinary scintillation performance with light yield exceeding 80 000 photons per MeV, which is far superior to that of typical 3D CsPbX 3 PNCs (∼21 000 photons per MeV) and commercial scintillators, such as CsI:Tl (54 000 photons per MeV), Gd 2 O 2 S:Tb (60 000 photons per MeV), etc. 34–36 In addition, the softer crystal lattice endows 0D hybrid halides with more opportunities to accommodate or recognize small molecules accompanied by change of luminescence properties, acting as a special fluorescent probe with high selectivity and sensitivity.…”

Rational design and synthesis of scintillating lanthanide coordination polymers for highly efficient X-ray imaging

“…Recently, metal–organic scintillators (MOSs) such as metal–organic frameworks (MOFs) and metal–organic coordination polymers (CPs) 9–19 have been developed to overcome the limitations of pure inorganic or organic scintillators, which show broad application prospects. The metal centers of MOSs could be high-Z elements such as Pb 2+ , 11,12 Ba 2+ , 10 Hf 4+ and Zr 4+15 , 20 to improve the X-ray absorption coefficient.…”