Hybrid Cd ²⁺ -Based Halide Birefringent Crystals Achieving Tunable Dual-Color Emission for Multifunctional LED and Anticounterfeiting Applications

Tunable multicolor luminescent materials are of great significance in boosting the security of information encryption. Herein, one-dimensional (1D) (4-AMP) 2 Cd 3 Cl 10 ·4(H 2 O) (4-AMP = 4-(aminomethyl)pyridine) new crystals, with a broadband blue emission, were successfully grown by the solution method. A notably large birefringence of 0.158@546 nm and a short ultraviolet (UV) absorption cutoff edge of about 264 nm were determined, indicating a promising application as a UV birefringent material. The Mn 2+ -doping strategy was adopted to modulate its photoluminescence properties, and a series of (4-AMP) 2 Cd 3 Cl 10 ·4(H 2 O):xMn 2+ (x = 10%, 20%, and 40%) with tunable multicolor emission were synthesized. Strikingly, (4-AMP) 2 Cd 3 Cl 10 ·4(H 2 O):10%Mn 2+ also exhibited a photoexcitation-induced tunable blue and red dual-color luminescence. Remarkably, (4-AMP) 2 Cd 3 Cl 10 ·4(H 2 O):40%Mn 2+ demonstrates a bright red emission at 632 nm, achieving a high PLQY of 73.06%. Combined experimental and theoretical investigations reveal that the red luminescence originates from 4 T 1 (G)→ 6 A 1 (S) of Mn 2+, and the blue emission is principally attributed to organic units. Furthermore, LED devices and multifarious anticounterfeit encryption models were fabricated and designed to explore their applications. This work not only presents a novel UV-birefringent crystal to achieve tunable dual-color luminescence via dopant engineering but also provides a fresh mindset to expand their optoelectronic applications.