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Luminescent EuIII Complexes Immobilized on a Vermiculite Clay Surface



Vermiculite clays were leached with nitric acid and functionalized with (3-chloropropyl)trimethoxysilane. The resulting materials were modified with the methylimidazolium (MID) group to yield cationic surfaces. These materials were characterized by infrared spectroscopy, elemental analyses, and specific surface area. Tetrakis(β-diketonate)europate(III) complexes, [EuL4] [L = dibenzoylmethane (DBM) and thenoyltrifluoroacetone (TTA)], were immobilized on the vermiculite surface containing the imidazolium cation to yield hybrid surfaces named Vx-MID-EuL4 (x = 0, 1, and 2), in which x represents the acid nitric concentration in mol L–1 that is used in the leaching process. The highest luminescence intensities of the intraconfigurational-4f 5D07FJ transitions (for which J = 0, 1, 2, 3, and 4) arising from [EuL4] complexes were presented by the hybrid materials containing the amount of imidazolium cation, which depend on the leaching process. The excitation and emission spectra suggested an efficient intramolecular energy-transfer process from ligand-to-Eu3+ ion in the supported materials. The photoluminescent properties of the hybrid materials were investigated based on the emission quantum efficiency (η), experimental intensity parameters Ω2 and Ω4, and Einstein's emission coefficient (A0J). The values of these parameters for the V2-MID-EuL4 surface are close to those assigned to the [EuL4] isolated complexes, which indicates that hybrid vermiculite materials are promising red phosphors.