Influence of Stabilizing Ion Content on the Structure, Photoluminescence and Biological Properties of Zr1–xEuxO2–0.5x Nanoparticles

Abstract

Quasi-spherical nanoparticles of ZrO2 containing EuO1.5 from 2 to 15 mol.% were synthesized from the chlorides of the corresponding metals under hydrothermal conditions. The structural changes of Zr1–xEuxO2–0.5x (x = 0.02 ÷ 0.15) nanoparticles depending on the content of europium (III) ions were studied using the complementary methods (X-ray diffraction, electron microdiffraction, Raman and photoluminescence spectroscopy). It was shown that increasing the Eu3+ concentration in the Zr1–xEuxO2–0.5x nanoparticles leads to a transition from the equilibrium monoclinic zirconia phase to metastable tetragonal and cubic polymorphic modifications. In this case, the size of the nanoparticles decreases from 11.5 nm to 9 nm; the specific surface area grows from 80.2 to 111.3 m2/g, and the electrokinetic potential increases monotonously from −8.7 to 16.3 mV. The evolution of the phase composition of Zr1–xEuxO2-0.5x nanoparticles from monoclinic to tetragonal/cubic allomorphs with an increase in the molar fraction of stabilizer ions was correlated with changes in the sublevel structure of 5D0 → 7F2 and 5D0 → 7F4 optical transitions for Eu3+ in the luminescence spectra. Besides, for the nanoparticles obtained by hydrothermal synthesis from chlorides, the quantum efficiency does not exceed 3%. According to the M.T.T. assay, as a result of three-day human fibroblast cultivation in the aqueous dispersion of Zr1–xEuxO2–0.5x (x = 0.02 ÷ 0.15) nanoparticles, the proliferation activity of the cells is maintained, indicating that they do not have cytotoxic properties. Such nanoparticles can be used in organic–inorganic composites for medical applications in order to strengthen the polymer scaffolds and visualize changes in their structure within time.

Charge Compensation in Europium-Doped Hafnia Nanoparticles: Solvothermal Synthesis and Colloidal Dispersion

“…Indeed for doping levels exceeding 3 at.% the thermodynamically stable monoclinic phase of hafnium was not anymore the only favourable crystal structure, often leading to the simultaneous appearance of the cubic polymorph. A similar behaviour was also reported for zirconia with stabilization of cubic/tetragonal polymorph from 0.5 at.% on [7][8][9][10][11]. The origin of these structural modifications are attributed to the charge mismatch at the doping lattice site, and the consequent creation of defects by the substitutional doping.…”

Metal Oxide Nanoparticles: An Effective Tool to Modify the Functional Properties of Thermally Stable Polyimide Films

“…The precipitate was dried at 100 • C to constant weight and then subjected to hydrothermal treatment. A four-h isothermal treatment of ZrO(OH) 2 under hydrothermal conditions at 250 • C and a pressure of 15 MPa led to the formation of nanocrystalline zirconium dioxide with a large number of hydroxyl groups remaining on their surface (Figure S1) [26]. The resulting powder is designated ZrO 2(hydroph) .…”

Rare Earths Doped Materials

“…All publications in this Special Issue are original contributions. Different materials doped with Rare Earth Elements are presented in the publications, among them nanoparticles of Zr 1-x Eu x O 2-0.5x [1], fluoridated hydroxyapatite [2], Bi 12 GeO 20 sillenite bulk crystals [3], GdSb 2 O 4 Br, TbSb 2 O 4 Br [4], and LuVO 4 [5].…”

“…The influence of the Rare Earth Element Eu on the crystal structure of the host matrix was investigated by increasing the Eu 3+ concentration in Zr 1-x Eu x O 2-0.5x nanoparticles (x = 0.02 ÷ 0.15) according to Bugrov et al [1]. A transition from the equilibrium monoclinic zirconia phase to metastable tetragonal and cubic polymorphic modifications was observed.…”

“…A transition from the equilibrium monoclinic zirconia phase to metastable tetragonal and cubic polymorphic modifications was observed. The nanoparticles can be used in organic-inorganic composites for medical applications and show changes in the structure with time [1].…”