Aggregation‐Induced Upconversion Luminescence of Ultra‐High‐Brightness Lanthanide Organic Cages X‐ray Scintillators

ABSTRACT In this work, aggregation‐induced emission luminogen (AIEgen) were used as ligand to achieve the first aggregation‐enhanced ligand triplet‐mediated cooperative sensitized upconversion luminescence (UCL), which greatly enhanced the UCL of a series of lanthanide organic cages in non‐deuterated solvent systems and aqueous solutions. The UCL intensities of the Yb 2 Eu 2 (L) 4 (Phen) 4 and Yb 2 Eu 2 (L) 4 ( S ‐BI) 4 increased by up to 3.6 and 14.3 times, respectively, compared with those of the molecular states, and their quantum yields increased by up to 3.8 and 19.2 times, respectively. To our knowledge, this is the first time that molecular UCL of lanthanide organic cages with precise structures in aqueous solutions has been achieved. The aggregation‐enhanced antenna effect of AIEgen in aqueous solution significantly enhances the luminescence of lanthanide organic cages and promotes their specific targeting to lipid droplets optical imaging. The synergistic effect of coordination‐induced emission and antenna effect, the Eu 4 (L) 4 ( S ‐BI) 4 scintillator exhibits a high light yield of up to 20241 photo/MeV, an ultra‐low detection limit of 27.2 nGy/s, which is 202 times lower than the clinical standard (5.5 µGy/s), and a radiation stability cycle of 96.8%, achieving low‐dose X‐ray imaging. To our knowledge, this is the first time that the lanthanide organic cage has been extended to targeted imaging of lipid droplets and X‐ray scintillator imaging, opening a new era for the application of lanthanide complex emitters in high‐resolution imaging.