Humidity and ultraviolet modulate color turned LnNa-based metal–organic frameworks as Bi-decryption anti-counterfeit materials

Abstract

Dynamic multi-decryption with luminescent anti-counterfeit materials still presents a challenge in information storage and security. In this work, Gd³⁺ is introduced into the structure of lanthanide-based metal–organic frameworks (LnMOFs) ([LnNa(HL²)₂(H₃L²)_0.5]·EtOH, H₃L² = 5-hydroxy-isophthalic acid, abbreviated as LnHIP) to adjust the Ln–Ln distances. The emission intensity of Tb³⁺ and Eu³⁺ reached a maximum with the dilution rate of Gd³⁺ fixed at 50%. The temperature-dependent luminescent properties reveal thermal stability even at an ultra-low temperature. The developed samples present water sensitive properties, thus the luminescence could be quenched by water atomization. Furthermore, by combining inkjet printing and the water quenching effect, the encrypted information could be decrypted by ultraviolet irradiation and water atomization successively. These results demonstrate the promising applications of LnMOFs in dynamic information decryption with Gd³⁺ doping to save cost and enhance luminescence intensity.