Lanthanum trifluoride nanoparticles prepared using ionic liquids

Lanthanum fluorides are important materials for their optical properties especially in the form of thin film or nanoparticles. In this paper we describe preparation of LaF3 nanoparticles by simple one-step synthesis. Ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) was used both as fluorination agent and solvent in the first preparation method and KPF6 (fluorination agent) dissolved in ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl) in the second synthesis procedure. In both cases liquid La(NO3)3 was used as the source of lanthanum. Reaction was performed at 200 °C for 90 min. Obtained white powders were washed by distilled water and methanol, dried on air and analyzed by Nanophox (particle size distribution), X-ray diffraction and by SEM and HRTEM. Nanoparticles of pure LaF3 were prepared and their size was estimated from X-ray pattern to be 11.0 and 11.6 nm in the first and second case, respectively. Sizes of nanocrystals were conformed by HRTEM. It was observed by SEM that nanoparticles tend to form irregular aggregates and their average size was estimated by Nanophox. Although nanocrystals prepared by both ways are of very similar size, the sizes of their aggregates differ significantly (730 nm from bmimPF6 vs. 3600 nm from KPF6 in bmimCl).