Nano Organic Co‐Crystal Scintillator for X‐ray Imaging

Traditional‐metal‐containing scintillators are widely used in X‐ray imaging due to their efficient X‐ray absorption and output of visible light. However, they suffer from heavy‐metal toxicity, environmental stability, harsh preparation, and afterglow. Metal‐free organic scintillators show a rising momentum, especially organic‐halogen‐containing molecules. Halogens are introduced to improve their X‐ray absorption, but the resulting increase in spin–orbit coupling leads to significant delayed fluorescence or phosphorescence, affecting the response speed to X‐rays. Moreover, there is still insufficient practice in fabricating microstructured organic scintillators for high spatial resolution of imaging. Herein, the preparation of nano organic co‐crystals (t‐Bpe‐IFB co‐crystal, abbreviated as BIC, t‐Bpe for trans‐1,2‐bis(4‐pyridyl)ethylene, and IFB for 1,3,5‐trifluoro‐2,4,6‐triiodobenzene) and its application in X‐ray imaging are explored. In contrast to previous single organic‐halogen‐containing molecules, BIC generates nanosecond‐scale fluorescence through the charge‐transfer state of the donor–acceptor. Its high iodine content ensures large X‐ray absorption, strong radioluminescence, and a low detection limit of 85 nGy_air s⁻¹. The composite film made of nano‐sized BICs and polydimethylsiloxane exhibits a high spatial resolution of 16.7 lp mm⁻¹. Herein, the application of organic co‐crystals is expanded and ideas are provided for the development of new scintillators.