Copper(I) Iodide–Hexamethylenetetramine Complex as Stable Scintillator for Free-Standing Flexible and High-Resolution X-ray Imaging Screens

The organo–inorganic coordination polymer Cu6I6(HMTA)2 (HMTA – hexamethylenetetramine) has been explored as a scintillator for X-ray imaging applications. This material, synthesized from readily available precursors via a scalable solution-based method, exhibits high photoluminescence quantum yield (>95%) and exceptional thermal and radiation stability. Composite scintillation screens (CSS) were fabricated by embedding Cu6I6(HMTA)2 nanoparticles into an ethylene-vinyl acetate (EVA) matrix, achieving high phosphor loading (up to 75 wt %) while maintaining mechanical flexibility. These CSS exhibited a maximum light yield of 63,500 photons/MeV and spatial resolution up to 18 lp/mm (line pairs/mm). Thin-film scintillators, produced by depositing Cu6I6(HMTA)2 on porous membranes, achieved an even higher spatial resolution of 24.5 lp/mm but showed reduced mechanical robustness. Remarkably, Cu6I6(HMTA)2-based screens demonstrated superior radiation stability, retaining 95% of their initial radioluminescence intensity after exposure to high X-ray doses (∼100 Gy). These results highlight the potential of Cu6I6(HMTA)2 as a high-performance scintillator for X-ray imaging applications.