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1
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Mechanochemical synthesis of thenoyltrifluoroacetone-1,10-phenanthroline europium complex

100%
Zaharieva J., Milanova M., Todorovsky D.
Open Chemistry
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2012
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vol. 10
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issue 6
1907-1912
EN
The paper considers the possibilities for mechanochemical synthesis of rare earth complexes. The complex Eu(TTA)3·phen (HTTA - 2-thenoyltrifluoroacetone, phen - 1,10-phenanthroline) is synthesized by mechanical treatment of a mixture of EuCl3.6H2O, HTTA, phen and NaOH in planetary ball mill Pulverisette 7 for 30 min at 800 min−1. The non reacted starting reagents and reaction side products are separated by treating activated mixture with water-ethanol solution following a procedure proposed in the literature. The elemental composition, X-ray diffraction pattern, IR spectra, optical properties (excitation and emission spectra, luminescence lifetime) and morphology of the mechanochemically synthesized complex are compared with those of the complex prepared from solution by the conventional method. The results confirm close similarity in the molecular structure and identity of the elemental composition, X-ray diffractograms and fluorescence properties of the compounds prepared by both methods. [...]
2
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Synthesis and characterization of Al-and Y-Al-citrates as potential precursors for YAlO3

100%
Petrova N., Todorovsky D., Kovacheva D., Milanova M.
Open Chemistry
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2006
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vol. 4
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issue 4
632-645
EN
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 Y4All2O9 are found by X-ray diffractometry.
3
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Mechanochemical synthesis of some europium diketonates

100%
Zaharieva J., Milanova M., Todorovsky D.
Open Chemistry
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2011
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vol. 9
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issue 2
290-299
EN
Results on the influence of mechanoactivation (3–30 min) in a planetary ball mill on the composition, crystal structure, IR spectra and morphology of EuCl3·6H2O, dibenzoylmethane (HDBM) and mixtures of EuCl3·6H2O - HDBM and EuCl3·6H2O - HDBM - 1,10-phenathroline (phen) are presented. Mechanoactivation leads to a decrease of interplanar distances of the EuCl3·6H2O and HDBM and partial synthesis of Eu(DBM)3 and Eu(DBM)3·phen in the respective mixtures. The fluorescence properties of the products of activation (excitation and emission spectra, lifetime of the excited states) are similar to those of the complexes produced by the conventional “wet” methods, but the strongest excitation of the mechanochemically produced solid state samples is achieved at higher wavelength. Crystals of different forms (prismatic, needle-, long-length-leaf- and rod-like) are formed by mechanoactivation of the mentioned mixtures.
4
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Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO3 and La1−xCaxMnO3

100%
Petrova N., Todorovsky D., Vasileva V.
Open Chemistry
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2005
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vol. 3
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issue 2
263-278
EN
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 LaxCa1−xMnyO3, produced from LaCaMn-citrate.
5
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Influence of complexation on the composition of equilibrium phases in the system of Ce2(SO4)3-La2(SO4)3

88%
Milanova M., Todorovsky D., Balarew C., Minkova N., Ivanova K.
Open Chemistry
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2007
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vol. 5
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issue 1
13-19
EN
The cocrystallization of Ce2(SO4)3 and La2(SO4)3 is studied in aqueous and H2SO4 (150 g/dm3) solutions at 25 °C and 64 °C. The effect of the formation of inner sphere sulfate complexes of the type LnSO 4+ in determining the composition of the equilibrium phases is revealed. [...]
6
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The photocatalytic degradation of 17α-ethynylestradiol by pure and carbon nanotubes modified TiO2 under UVC illumination

88%
Kralchevska R., Milanova M., Bistan M., Pintar A., Todorovsky D.
Open Chemistry
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2012
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vol. 10
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issue 4
1137-1148
EN
Commercial 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.
7
Content available remote

Influence of ThO2 on the photocatalytic activity of TiO2

76%
Kralchevska R., Milanova M., Kovacheva P., Kolev J., Avdeev G., Todorovsky D.
Open Chemistry
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2011
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vol. 9
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issue 6
1027-1038
EN
Microcomposites consisting of TiO2 (or Ce-doped TiO2) and ThO2 (0.5–2% of the TiO2 mass) are produced by sol-gel synthesis of TiO2 in presence of ThO2. X-ray diffraction study reveals the effects of ThO2 (compared to the ThO2-free TiO2, obtained by the same method) on the anatase interplanar distances, crystallites size and phase composition. The photocatalytic tests in presence of the composites under UV irradiation reveal an increase of the Malachite Green degradation rate constant. The effect depends on the Th relative content, temperature of annealing of the catalyst and addition of other doping agent. The highest photocatalytic activity is observed for TiO2 obtained at 550°C and containing 1% ThO2. The composite exhibits activity in dark, also. The presence of Ce4+ ions is not an obligatory requirement for the realization of the ThO2 effect. The reported results suggest that the radioactivity of the Th and/or its decay products is one of the main factors responsible for the increased photocatalytic activity of TiO2. [...]
8
Content available remote

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

76%
Milanova M., Kovacheva P., Kralchevska R., Kolev J., Zaharieva J., Todorovsky D.
Open Chemistry
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2012
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vol. 10
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issue 6
1850-1858
EN
Microcomposites consisting of TiO2 and ThF4 or UO3 (0.5–2% 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. [...]
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