Europium(III) Fluoride Nanoparticles from Ionic Liquids: Structural, Morphological, and Luminescent Properties

Inorganic luminescent materials (phosphors) find widespread scientific and industrial applications. For potential applications, nanoscale phosphors are favored because of the reduced scattering and the possibility to miniaturize devices. In such materials, the optical behavior is strongly dependent on impurities or defects in the crystal lattice, so that a well-defined reaction protocol with fixed parameters is compulsory to ensure the quality of the obtained material. The fast and facile conversion of europium acetate via microwave radiation with and in different tetrafluoroborate ionic liquids to oxygen-free, hexagonal EuF3 nanoparticles is investigated in detail. The study of the influence of the different reaction parameters on the structural, morphological, and luminescent properties predominantly reveals a strong influence of the chosen ionic liquid. The particle morphology varies from small spherical particles to rods forming different types of aggregates, such as bundles, columns, or spherical agglomerations. The luminescence spectra show the characteristic orange-red emission due to the dominating D-5(0) -> F-7(1) transition of Eu3+. The D-5(0) quantum efficiency could be tuned from 2% up to 44% depending on the ionic liquid used for synthesis.