Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO<Subscript>3</Subscript> and La<Subscript>1−x</Subscript>Ca<Subscript>x</Subscript>MnO<Subscript>3</Subscript>

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn₃O₄ (hausmannite) and LaMnO₃ respectively. Parasitic phase(s) are observed in La_xCa_1−xMn_yO₃, produced from LaCaMn-citrate.     

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.     

Synthesis and IR-Spectral Characterization of Mixed-Ligand Solid State Complexes of Some Lanthanoides with Mono-(2-ethylhexyl) Phosphoric Acid

The synthesis of a new type of complexes of Y, Nd and Er with mono-(2-ethylhexyl) phosphoric acid is reported. The elemental composition, IR-spectral data and thermogravimetric analysis prove the presence of both mono-and bivalent ions of the acid as ligands as well as of NO₃-ions. The IR-spectrum is interpreted in comparison with those of other lanthanoid complexes of the same acid.     

On the spray-drying deposition of TiO2 photocatalytic films

The photocatalytic activity of TiO₂ films deposited on different substrates by the spray-drying method using suspensions of commercially available TiO₂ (Degussa P25 or Tronox) as starting material was studied. The influence of the type of the initial TiO₂, preparation conditions (temperature of the substrate during the film deposition, temperature of the post-deposition annealing), substrate material (glass, fused silica, stainless steel and graphite), the presence of additives in the spraying suspension (polyethylene glycol, ethylene glycol and acetylacetone) and its sonication before spraying on the morphology, size of crystallites and phase composition (rutile/anatase ratio) was studied. Optimal conditions for spray deposition of the films are suggested.     

The radioactivity and the chemical nature of additives as factors determining the photocatalytic activity of TiO2

Microcomposites consisting of TiO₂ and ThF₄ or UO₃ (0.5?C2% of the TiO₂ mass) are produced by sol-gel synthesis of TiO₂ in presence of the respective additives. X-ray diffraction study reveals small effect of the latter on TiO₂ phase composition and cell parameters and significant influence on the crystallite size and UV/Vis reflectance spectra. The photocatalytic tests in presence of TiO₂-ThF₄ microcomposites under UV and solar irradiation show a non-monotonic increase of the Malachite Green degradation rate constant with the increase of ThF₄-content. No changes in the photocatalytic activity are observed in the presence of UO₃ but the latter composites exhibit activity in darkness. The results are compared with previously reported data on the performance of TiO₂-ThO₂ photocatalyst with the same radioactivity and suggest that both radioactivity and the chemical nature of the dopants are responsible for the photocatalytic performance of TiO₂-based composites containing radioactive substances.      

Synthesis and characterization of Al-and Y-Al-citrates as potential precursors for YAlO3

Al-and Y-Al-citric complexes have been synthesized in ethylene glycol medium at conditions close to the ones used in polymerized complex method and their composition and spectral characteristics have been studied. Proofs have been found for the formation in the bimetallic system of a mixed-metal Al-Y-complex. Doubly ionized and esterified ligands take place in the Al-complex. All of the ligands forming Y-Al-complex are mono-or doubly esterified. Deprotonation of the alcoholic group takes place in the formation of the mixed-metal complex. Both complexes contain adduct-bonded ethylene glycol. Heating of the bimetallic complex or of the polyester resin formed leads to not phase-homogeneous YAlO₃-along with cubic YAlO₃, its orthorhombic modification as well as Y₄Al _l2O₉ are found by X-ray diffractometry.     

Cerium(III/IV) and Cerium(IV)–Titanium(IV) Citric Complexes Prepared in Ethylene Glycol Medium

Summary. Cerium(III/IV) and Ce(IV)–Ti(IV) citric complexes were synthesized in ethylene glycol medium under conditions similar to those of the polymerized complex method (PCM). Solution phase ¹H, ¹³C NMR, solid state ¹³C CP MAS NMR and IR spectroscopy, and X-ray powder diffractometry were used to characterize the composition and structure of the synthesized products. Thermal decomposition of the isolated complexes was studied and a scheme of the processes taking place is proposed. Complexes of Ce(III) can be prepared at low temperature (40°C), only. In the presence of Ti(IV) ions, the oxidation takes place even at this temperature. A mixed-metal nature of the Ce(IV)–Ti(IV) complexes is established. The comparison between their composition and the one of analogous lanthanide(III)–Ti(IV) citrates contributes to the elucidation of the complexation process mechanism in the case of the PCM application. The increased charge of the complexation agent in the Ce⁴⁺–Ti⁴⁺ complex (in comparison with Ln ³⁺–Ti⁴⁺ citrates) is “compensated” by the increase of the relative number of the ligands with deprotonated OH group.