The synergy of inorganic cluster cage and organic ligands in lanthanide-titanium-oxo clusters scintillators for high performance X-ray imaging

With the increasing demand for X-ray imaging, especially for three-dimensional imaging of curved and irregular objects, the development of high-performance flexible scintillation films has attracted significant interest. Lanthanide(III)-organic scintillators have recently emerged as a new promising class of X-ray scintillators for their great flexibility in structural design and optical tuning. However, designing lanthanide(III)-organic scintillators with high light yields and good solution dispersibility is still challenging. Herein, a europium-titanium oxo cluster (Eu-TiOC) scintillator with highly-efficient X-ray excited luminescence and good solution dispersibility is reported. The cage-like lanthanide-titanium oxo cores served as X-ray absorbers to produce high-energy electrons, initiating secondary electron thermal relaxation. Organic ligands functioned as energy transfer bridges and antennas, sensitizing Ln³⁺ ions’ luminescence through cascaded energy transfer processes. As a result, the Eu-TiOCs scintillator exhibited high steady-state X-ray light yields (up to 26,816 ± 2000 photons MeV⁻¹). In addition, the weak hydrogen bonding interaction between the Eu-TiOCs and the polymer enhanced the solution dispersibility of Eu-TiOCs, facilitating the preparation of low light-scattering and uniform scintillation films. By the synergy between the inorganic cluster cage and organic ligands, the resulting flexible scintillation film achieved a high spatial resolution of 12.8 lp mm⁻¹ and enabled low-dose X-ray imaging for both planar and non-planar objects.