Organic Cation Methylation Design of Hybrid Eu(II)-based Halide Scintillators for Improved X-Ray Detection and Imaging.

Organic-inorganic hybrid scintillators (OIHSs) have emerged as promising candidates for X-ray imaging. However, inhibiting the concentration quenching effect and reducing vacancy defects remain major challenges for high-performance OIHSs. Herein, a modification strategy of organic cation methylation is introduced to prepare PDMIMEuX3 (PDMIM-X, PDMIM = 1-Propyl-2,3-dimethylimidazolium, X = Br, I) upon PMIMEuX3 (PMIM-X, PMIM = 1-Propyl-3-methylimidazolium). Benefiting from the increased Eu-Eu chain spacing and structural rigidity by the steric effect of inserted cationic methylation, PDMIM-X suppresses nonradiative recombination between luminescent centers and the halogen vacancy defects. Particularly, PDMIM-Br designed via such a cation methylation exhibits high light output, which is 3.57 and 9.7 times higher than that of commercial Lu3Al5O12:Ce and original PMIM-Br, respectively, and thus it also demonstrates a low detection limit of 42.61 nGy s-1. Moreover, leveraging the capability of rapid in situ solution processing, a transparent and large-area PDMIM-Br@film is prepared with a spatial resolution of 21.1 lp mm-1 for X-ray imaging. This study developed high-performance OIHSs and further provided an effective strategy via materials design to improve the detection and imaging capabilities.