Structural, spectroscopic and cytotoxicity studies of TbF₃@CeF₃ and TbF₃@CeF₃@SiO₂ nanocrystals

Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF₃@CeF₃ and TbF₃@CeF₃@SiO₂ nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO₂ shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF₃@CeF₃ nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, 'the products', with an average diameter around 10 nm, showed an increase in the concentration of Tb³⁺ ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO₂ shell.

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