Lanthanide-Directed Luminescent “Soft” Coordination Polymer Gels: White Light Emission, Anticounterfeiting, and Thin-Film-Based Sensing

Stimuli-responsive light-emitting materials are of great interest owing to their potential use in encryption and multilevel security. In this context, herein, the synthesis of light-emitting multifunctional coordination polymer gels (CPGs) was accomplished by the self-assembly of europium and terbium acetate with a bifunctional (amide/carboxylic acid) gelator. The as-synthesized luminescent CPGs are stable up to 300 °C. The FESEM micrograph exhibits pebble-like morphology, and the TEM images reveal a sheet-like structure which is grown on top of each other. The optical properties of the as-synthesized CPGs are readily tuneable over a broad spectrum, including white-light emission, simply by modulating the europium and terbium ion stoichiometry. The as-synthesized luminescent materials have the potential to be used as invisible security inks for high-security information encoding. Additionally, water-resistant luminescent thin films were fabricated by incorporating Eu@BTT or Tb@BTT (BTT: 5,5′,5″-((benzene-1,3,5-tricarbonyl)tris(azanediyl))triisophthalic acid) into the poly(methyl methacrylate) (PMMA) polymer matrix for the naked eye test of nitro-explosive compounds (2,4,6-trinitrophenol and nitrophenol). The sensing mechanism is proposed based on the DFT and time-resolved photoluminescence studies.