Dual-band-tunable all-inorganic Zn-based metal halides for optical anti-counterfeiting

Low-dimensional lead-free metal halides have emerged as promising candidates for anti-counterfeiting applications, characterized by their low toxicity, diverse crystal structures, and exceptional optical properties. Conventional anti-counterfeiting technologies based on low-dimensional metal halides are often constrained by complex and time-consuming heating and solvent treatments that may insufficiently modify the luminescent characteristics of emitters, thus hindering their practical implementation in effective anti-counterfeiting strategies. In this study, we employ an innovative alloying strategy in low-dimensional zinc halides Cs₂ZnCl₄ to enhance their luminescent performance. By introducing self-trapped exciton (STE) states through the alloying of Cu⁺ and Sb³⁺ ions in Cs₂ZnCl₄, we achieve bright blue and red photoluminescence (PL) centered at 492 nm and 744 nm, respectively, under 266 nm excitation, with only red emission observed under 365 nm excitation. This approach enables instant and reliable anti-counterfeiting applications. This work presents new opportunities for developing robust anti-counterfeiting and information encryption/decryption technologies.