Heavy‐Metal‐Free ZnSeTe Quantum Dots‐Based Liquid Scintillators for Scalable X‐Ray Imaging

ABSTRACT Quantum dot (QD)‐based scintillators show promise for use as flexible X‐ray imaging screens due to their high performance and scalable characteristics. However, conventionally used QD‐based scintillators face severe limitations, including poor chemical stability and unavoidable toxic issues arising from heavy metals such as cadmium (Cd) or lead (Pb). Herein, a Cd/Pb‐free liquid scintillator based on ZnSeTe‐based core‐shell QDs and an energy transfer donor molecule of 2,5‐diphenyloxazole (PPO) is reported, which offers high efficiency and scalability. By adjusting the Te/Se ratios of ZnSeTe, an optimal balance between X‐ray absorption and radioluminescence efficiency of ZnSeTe‐based core‐shell QDs is achieved, resulting in a blue‐emitting scintillator with a light yield of 11 222 (±2%) photons MeV ⁻¹ beyond commercial Bi ₃ Ge ₄ O ₁₂ . Furthermore, halogen passivation effectively eliminates trap states on the surface of ZnSeTe‐based core‐shell QDs, doubling the X‐ray‐excited fluorescence intensity. Consequently, the composite liquid scintillator, fabricated using PPO‐composited ZnSeTe‐based QDs, achieves a high light yield of 33 450 (±5%) photons MeV ⁻¹ and a low detection limit of 788.4 nGy s ⁻¹ . High‐performance X‐ray imaging with a spatial resolution of 6.7 line pairs (lp) mm ⁻¹ is achieved. This work introduces a novel approach for the development of eco‐friendly QD‐based scintillators with structural and optical modulation for high‐performance X‐ray imaging.