Rare Earth Complexes as Optical Markers for Antibiotics in Paper-Based Tests

Rare earth elements exhibit unique photoluminescent properties arising from 4f–4f electronic transitions, which makes these compounds of strategic and commercial interest. In this work, terbium-based complexes were synthesized using flufenamic acid (fluf) as a ligand. The main objective of this study was to evaluate these complexes as optical markers for the identification of tetracycline and oxytetracycline antibiotics in aqueous media, employing paper-based rapid tests. For this purpose, paper substrates were impregnated with the complexes and, after applying a drop containing the antibiotic, luminescence quenching of the material was observed.