Luminescent and magnetic materials with a high content of Eu3+-EDTA complexes

Abstract

Bifunctional optical magnetic materials with a high europium content have been prepared. Chelating groups were introduced on the Fe₃O₄ surface with organosilanes containing ethylenediaminetetraacetic acid (EDTA) derivatives, which were previously prepared via a reaction between EDTA-dianhydride and aminoalkoxysilane agents: 3-(trimethoxysilyl)propylamine (1N), N-[3(trimethoxysilyl)propyl]ethylenediamine (2N) and N¹-(3-trimethoxysilylpropyl)diethylenetriamine) (3N). The first coordination sphere of Ln-EDTA complexes present on the modified surfaces of Fe₃O₄ particles was completed by addition of β-diketonate ligands (tta: thenoyltrifluoroacetone, dbm: dibenzoylmethane, bzac: benzoylacetone and acac: acetylacetone) in order to improve their luminescence properties. The materials were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and wavelength dispersive X-ray fluorescence (WDXRF) and Fourier-transform infrared (FT-IR) spectroscopy as well as by zeta potential measurements and luminescence spectroscopy. The hybrid materials exhibited intense red emission, which can be assigned to the 4f–4f transitions of the Eu³⁺ ion, indicating an efficient intramolecular ligand-to-metal energy transfer. The experimental intensity parameters (Ω₂ and Ω₄), lifetimes (τ), as well as radiative (A_rad) and non-radiative (A_nrad) decay rates of the Eu³⁺ ion were determined and discussed. The strategies used to obtain these materials may contribute to the development of several bifunctional systems for practical applications.