Enhanced Photoluminescence Properties of Polyhedral Oligomeric Silsesquioxane-Based Hybrid Phosphors for Anti-Counterfeiting and Flexible Composite Applications

We have described a novel organic-inorganic hybrid polyhedral oligomeric silsesquioxane (POSS) type monomer ligand 2,6-pyridinediamine-bis-propanylheptaisobutyl POSS (PDC-POSS) and synthesized it using rare-earth (RE = Eu3+, Tb3+) doped hybrid complex PDC-POSS phosphors. The PDC-POSS precursor was prepared by (3-aminopropyl) heptaisobutyl POSS, 2,6-pyridinedicarboxylic acid chloride (PDC), and then coordinated with RE3+ using europium and terbium nitrate regents to yield PDC-POSS:RE3+ phosphors. Under UV light (A = 285 nm) excitation, photoluminescence (PL) spectra of Eu3+-doped PDC-POSS were detected at 591, 615, 650, and 693 and those of Tb3+-doped PDC-POSS were monitored at 488, 544, 584, 619, and 647 nm. The thin films with good transmittance were deposited from aqueous colloidal solution of hybrid phosphors on bank notes, plastic card substrates, and cotton fibers to demonstrate the transparency of phosphor thin films, which are feasible for use in anti-counterfeiting applications, which require concealment and identification by the naked eye. In addition, a polymer composite with good flexibility that can be applied to LED chips and display was produced. Finally, it was suggested that PDC-POSS:RE3+ phosphors can be used in various applications.