Estudo da estabilidade de complexos de Eu3+ em espuma de poliuretano com potencial uso como marcador luminescente anti-falsificação

Abstract

Lanthanide­based complexes play an important role as luminescent markers. The interaction between luminescent complexes and polymers contributes to their widespread application in information encryption and anti­counterfeiting, protecting the security and privacy of various products such as medicines, official documents, and electronic devices. However, markers with low optical stability limit their application prospects, necessitating the search for chemically stable markers that are tolerant to UV exposure. This study synthesizes, characterizes, and investigates the emission stability of the [Eu(bmdm)3(H2O)2] and [Eu(tta)3(H2O)2] complexes in polyurethane foams, exploring the potential application of this system in anti­counterfeiting processes. Both complexes were synthesized with a 1:3 molar ratio of Eu3+ and bmdm (1­(4­Methoxyphenyl)­3­(4­tert­butylphenyl)propane­1,3­dione) or tta (2­ thenoyltrifluoroacetone) ligands and inserted into the polymer matrix during polymerization at proportions of 1, 3, and 5 % w/w. Subsequently, the composites were characterized by techniques such as ultraviolet spectroscopy, revealing that the intensity of the bands increases proportionally to the increase in the concentration of the complex in the foams. The interaction between the complex and the foam was confirmed by infrared spectroscopy, while the emission in the visible region was evaluated by photoluminescence spectroscopy, revealing that all the transitions present in the pure complexes were maintained, since the peaks remained in the same positions, without band broadening. Stability tests were conducted through photostability analysis, which indicated that composites containing [Eu(bmdm)₃(H₂O)₂] present greater stability to photodegradation. However, Eu­Pus containing [Eu(tta)₃(H₂O)₂] presented greater contribution to the formation of a thermally stable material. Stability tests against metallic contaminants were performed by exposing the composites (Eu­Pus) to Cu²⁺, Fe²⁺, and Pb²⁺ ions in different solvents (water and alcohol), which were subsequently analyzed. Analysis of the excitation and emission spectra allowed us to conclude that the interaction with these contaminants did not result in significant changes in emission suppression, demonstrating the stability of the materials. These results indicate that the combination of these materials presents high stability and potential for the development of resistant luminescent markers.