Hybrid copper(I) halides with excitation-dependent dual-color emission for X-ray imaging and multimode encryption.

Hybrid copper(I)-based halides are important materials in radiation detection and anticounterfeiting owing to their excellent luminescence efficiency and low toxicity. This study employed a chiral racemic strategy to synthesize (Rac-MPZ)CuI (where MPZ represents 2-methylpiperazine) single crystals with excitation-dependent dual-color emission. (Rac-MPZ)CuI has a zero-dimensional crystal structure, which is different from the two-dimensional structure of chiral (R/S-MPZ)CuI. Interestingly, (Rac-MPZ)CuI exhibits excitation-dependent cyan and red emissions at room temperature (298 K), with the photoluminescence quantum yield of the cyan emission peak approaching 90 %. Its luminescence mechanism is proposed through density functional theory calculations and theoretical experiments. (Rac-MPZ)CuI exhibits excellent X-ray absorption and responsivity, with a light yield of up to 34,500 photons/MeV. X-ray imaging screens developed with (Rac-MPZ)CuI show an excellent resolution of >10 lp/mm. Therefore, the synthesized material has great potential for practical applications as a scintillator. In addition, its unique excitation-dependent dual-color emission property at room temperature and temperature-dependent thermochromicity have excellent potential in anticounterfeiting and information encryption, which can realize multimode and multilevel anticounterfeiting or encryption effects. This study also provides new prospects for developing multifield applications of copper(I)-based halides.