Water-Resistant Zero-Dimensional Hybrid Copper Halide for High-Efficiency X-ray Scintillation and Sensitive Fluorescent Probing

Low-dimensional hybrid metal halides, known for their highly tunable structures and exceptional photophysical properties, have attracted considerable interest for luminescent, optoelectronic, and sensing applications. In this study, we report on the synthesis and characterization of [ACPP]₂Cu₄Br₈ (ACPP = protonated 1-amino-4-cyclopentylpiperazine), a lead-free zero-dimensional organic-inorganic copper(I) halide with outstanding scintillation performance. The material achieves a high photoluminescence quantum yield (92.4%), an exceptional X-ray scintillation light yield (43,000 ± 300 photons MeV^-1), a low X-ray detection limit (0.139 μGy_air s^-1), and high-resolution X-ray imaging capability, making it a promising candidate for advanced X-ray imaging technologies. Furthermore, its crystals exhibit excellent emission stability in water and reversible fluorescence quenching with high sensitivity and selectivity toward nitrobenzene, which is an organic pollutant. These findings highlight the potential of this ecofriendly luminescent material for next-generation optical and sensing technologies.