M. Milanova

A simple solution route to the synthesis of pure La2Ti2O7 and Nd2Ti2O7 at 700–800°C by polymerized complex method

Abstract A polymerized complex technique was utilized to prepare high-purity La 2 Ti 2 O 7 and Nd 2 Ti 2 O 7 . Heating of mixed solutions of citric acid (CA), ethylene glycol (EG), La (or Nd) and Ti ions with a molar ratio of CA:EG:La(or Nd):Ti = 5:20:1:1 at 130°C produced a yellowish transparent polymeric gel without any precipitation, which has subsequently used as a precursor for the production of La 2 Ti 2 O 7 and Nd 2 Ti 2 O 7 . We suggest, based on the results of 13 C NMR spectroscopy, that mixed-metal chelate complexes. (La,Ti)-CA n or (Nd,Ti)-CA n , formed in starting CA-EG solutions. The formation of pure La 2 Ti 2 O 7 and Nd 2 Ti 2 O 7 occurred when the precursor was heat treated in a furnace set at 700°C and 800°C respectively in static air for 4 h.

Surface Roughness Characterization of Poly(methylmethacrylate) Films with Immobilized Eu(III) β-Diketonates by Fractal Analysis

The structural complexity of the 3-D surface of poly(methylmethacrylate) films with immobilized europium β-diketonates was studied by atomic force microscopy and fractal analysis. Fractal analysis of surface roughness revealed that the 3-D surface has fractal geometry at the nanometer scale. Poly(methylmethacrylate) (PMMA) as immobilization matrix is dense and uniform, and a tendency for formation of chain structures was observed. Fractal analysis can quantify key elements of 3-D surface roughness such as the fractal dimensions D f determined by the morphological envelopes method of the Eu(DBM)3 and Eu(DBM)3 · dpp nanostructures, which are not taken into account by traditional surface statistical parameters.

Morphology and Optical Properties of SiO2-Based Composite Thin Films with Immobilized Terbium(III) Complex with a Biscoumarin Derivative

The complex of Tb(III) with the biscoumarin derivative 3,3′-[(4-hydroxyphenyl)methyl)]bis-(4-hydroxy-2H-1-benzopyran-2-one), Tb(C25H15O7)3 · 5H2O, was successfully immobilized by a simple technique in transparent SiO2-based matrix. The films and monoliths obtained were studied by IR spectroscopy, fluorescent spectroscopy, and microscopy. The micromorphology of the films was studied by atomic force microscopy, proving their homogeneity. The 3-D surface of the films is very complex geometrically and appears relatively smooth, with very fine nano-asperities spread on the surface due to the preparation process. A detailed surface description of the surface morphology at nanometer scale using statistical parameters, according to ISO 25178-2: 2012, was made. The presence of the Tb(III) complex in the films and monoliths was proven by the characteristic emission bands of the Tb(III) ions. The lifetime of the immobilized Tb(III) complex was determined, showing better protection of the SiO2 matrix in the monoliths than with the films.

Influence of mechanoactivation on rare earths leaching from phosphogypsum

Abstract The influence of mechanoactivation on the overall solubility of CaSO4 · 2H2O and of phosphogypsum in water and in diluted acids (10% HCl, 7% H2SO4) as well as on the leaching of rare earths from phosphogypsum have been studied. The mechanoactivation is performed in a centrifugal ball mill in air and in suspension with the acids mentioned above. Part of the experimental results are qualitatively explained considering the partial dehydration of the CaSO4 · 2H2O during the activation in air as well as considering the crystal structure disrupted by mechanoactivation. A dissolved fraction, considerably enriched in rare earths (compared to the initial phosphogypsum) is obtained as a result of H2SO4 treatment of the samples activated in water solution.

SiO2/polyester hybrid for immobilization of Ru(II) complex as optical gas-phase oxygen sensor

Organic–inorganic hybrid materials produced from tetraethoxysilane, citric acid and ethylene glycol in different mole ratios and consisting of Si–O–Si and Si–O–C nets are prepared and their molecular structure (IR and NMR spectroscopy), morphology (fluorescent microscopy, SEM and AFM), thermochemical behavior and fluorescence properties (excitation and emission spectra) are studied. The optically active, oxygen sensitive complex of tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride is immobilized in the so prepared matrix and the applicability of the composite as an optical oxygen sensor (response to O2 in gaseous medium) is tested. The influence of the matrix composition on the linearity of the Stern–Volmer dependence and the films sensitivity to O2 is studied.

Lanthanide complexes with β-diketones and coumarin derivates:synthesis,thermal behaviour,optical and pharmacological properties and immobilisation

Abstract The paper presents the results of the synthesis of complexes of the type Eu(DBM) 3 and Eu(DBM) 3 ·Q (DBM-dibenzoylmethane, Q-1,10-phenantroline or 4,7-diphenyl-1,10-phenantroline) and of Tb- and Nd-complexes with the newly-synthesised coumarin derivates 3,3′-[(4-chlorphenyl)methylene)bis(4-hydroxy-2H-chromen-2-one), 3,3′-[(3,5-dimethoxy-4-hydroxy)methylene)bis(4-hydroxy-2H-chromen- 2-one), etc. Elemental and thermogravimetric analysis, IR, UV, NMR and fluorescence spectroscopy and X-ray analysis were applied for characterisation of the complexes. Some peculiarities of the synthetic procedures for both types of complexes were discussed and the influence of the synthetic approach, pH of the reaction medium, temperature of synthesis and drying of the complexes on the composition, stability and optical properties was reported. The immobilisation of the complexes in thin films based on sol-gel produced SiO 2 and on polymethylmethacrylate was studied. The optimal conditions for preparation of the matrices (composition of the starting system, temperature and time of sol aging, etc.) were recommended. The film morphology was evaluated by fluorescence, scanning electron and atomic force microscopy. The interaction of the lanthanide ions with the matrices and the influence of their nature, the effect of the in-situ polymerisation and other factors on photoluminescent excitation and emission spectra and excited state life-times of the complexes were followed. The effect of the second ligand on the photoluminescence properties of the immobilised diketonates was further elucidated. Processes involved in the thermal decomposition of the complexes and microcomposites produced on their base were proposed. Preliminary results on the pharmacological properties of the coumarin complexes reported showed unambiguously higher cytotoxicity of the Nd complex in comparison with that of the respective ligand.

Solubility of some lanthanide sulfates in polycomponent systems containing H2SO4

SummaryThe paper presents data on the solubility of La, Ce, Pr, Nd sulfates in the polycomponent system La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (at 25°C and 64°C) as well as in the same polycomponent system but in the presence of CaSO4·2H2O. The solubility of the sulfates — ocathydrates of Pr at 25°C and 64°C and of La and Ce at 64°C in tricomponent systemLn2(SO4)3·8H2O-H2SO4-H2O are also reported.ZusammenfassungDie Arbeit präsentiert Daten für die Löslichkeit von La-, Ce-, Pr- und Nd-Sulfaten in den Vielkomponenten-Systemen La2(SO4)3·8H2O-Ce2(SO4)3·8H2O-Pr2(SO4)3·8H2O-Nd2(SO4)3· 8H2O-H2SO4-H2O (bei 25°C und 64°C) sowie in den gleichen Systemen, jedoch in Anwesenheit von CaSO4·2H2O. Über die Löslichkeit von Sulfatoctahydraten von Pr bei 25°C und 64°C und von La und Ce bei 64°C in den Dreikomponenten-SystemenLn2(SO4)3·8H2O-H2SO4-H2O wird auch berichtet.

Thermal decomposition of yttrium, lanthanum and lanthanide benzene-1,3-dioxyacetates in an air atmosphere

Abstract The thermal decomposition in air of benzene-1,3-dioxyacetates of Y, La and lanthanides from Ce III to Lu III was studied. During heating, the hydrated complexes Ln 2 [C 6 H 4 (OCH 2 -COO) 2 ] 3 · n H 2 O ( n = 7–12) lose water of crystallisation in one (La-Nd, Eu, Lu) or two steps (Y, Ce, Sm, Gd-Yb), then decompose directly to oxides (Ce) or with intermediate formation of oxycarbonates: Ln 2 O 2 CO 3 (La, Pr, Sm-Ho), Ln 2 O 3 ·0.5CO 2 (Y, Er-Lu) or two types of oxycarbonates (Nd).

The photocatalytic degradation of 17α-ethynylestradiol by pure and carbon nanotubes modified TiO2 under UVC illumination

AbstractCommercial product Degussa TiO2 P25, sol-gel produced TiO2 and TiO2 modified by carbon nanotubes addition (5% of the TiO2 mass) are tested as photocatalysts for the degradation of endocrine disrupting compound 17α-ethynylestradiol (1 µM aqueous solution). The molecular and crystal structure, phase composition, crystallite size, specific surface area, pore average diameter, their area and volume distribution, morphology, IR and UV/Vis spectra of the catalysts are characterized. HPLC is used for estrogen analysis. The sorption ability and photocatalytic activity (measured by degradation rate constant and percentage of the pollutant conversion) of the catalysts under UV (17 W, emission maximum at 254 nm) irradiation is determined. Full destruction of the pollutant is reached after 30 min irradiation in presence of Degussa P25. The performance of some of the catalysts is compared with literature data for their activity under 365 nm-illumination.

Effect of the addition of rare earths on the activity of alumina supported copper cobaltite in CO oxidation, CH4 oxidation and NO decomposition

Abstract The effect of the addition of small amounts of rare earths (Ln=La, Ce, Nd and Gd) to alumina supported copper-cobalt spinel oxide on the catalysts efficiency in CO and CH 4 oxidation and in NO decomposition was investigated. Samples of Ln/CuCo/Al catalyst were prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), H 2 -temperature-programmed reduction (H 2 -TPR), electron paramagnetic resonance (EPR) spectroscopy and low temperature nitrogen adsorption. The results showed that the addition of rare earths changed the surface state of the alumina supported copper-cobalt spinel catalyst. As a result, partial reduction of copper species was observed as well as migration of these species between the surface and the bulk. The Ln/CuCo/Al catalysts behaved differently in oxidation and reduction processes. In oxidation processes where oxide structure was important, Ce/CuCo/Al and Nd/CuCo/Al were the most active catalysts. The catalyst Ce/CuCo/Al was the most active in the oxidation reactions because of the availability and favorable surface distribution of the redox couples Cu + /Cu 2+ and Ce 3+ /Ce 4+ . In NO decompostion, Ln-modified catalysts significantly improved the selectivity of the process to N 2 .