Display omitted
•Zinc containing layered double hydroxides (LDH) synthesis.•Propane dehydrogenation on the platinum catalysts based on Mg(Zn)Al-LDH.•Electronic state of platinum in the Pt/Mg(Zn)AlOx ...catalysts.
Layered double hydroxides (LDH) containing Al3+, Mg2+ and Zn2+ cations with the ratios of Zn/(Mg+Zn)=0, 0.05, 0.1, 0.2, 0.5, 0.7, and 1.0 were synthesized. The effect of zinc content on the phase composition of LDH and on the structural parameters, textural characteristics and acid–base properties of the corresponding mixed oxides were studied. This type of supports was used to obtain the non-acid platinum Pt/Mg(Zn)AlOx catalysts. The formation of supported platinum particles, their composition, dispersion and electronic state were examined by means of TPR, TEM, XPS, and EXAFS. The possibility to obtain the bimetallic PtZn particles, whose structure and strength of interaction with the support depend on the zinc content of the support, was demonstrated. It was found that the presence of zinc atoms in the platinum environment decreases the particle size of active metal and stabilizes platinum in the active metallic state ensuring a high activity of the catalyst in dehydrogenation of propane with the selectivity for propylene above 99%.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Ge/Si quantum dot (QD) structures doped with Mn have been tested by the EPR method to find the optimal conditions for formation of the diluted magnetic semiconductor (DMS) phase inside QDs. The ...effect of Mn doping has been studied for two series of samples: series A with QDs grown at 450°C and varied Mn concentration and series B with QDs grown at different temperature with Mn concentration
x
= 0.02. Several effects of modification of the EPR spectra due to Mn presence in the samples have been obtained. These effects are related to (i) strain reduction due to Ge—Si intermixing, (ii) QD enlargement and change in QD shape, (iii) presence of an additional magnetic field produced by Mn atoms incorporated in QDs. The data obtained allow us to understand the reasons for irreproducibility of the results available in the literature on the creation of magnetic Ge
1 −
x
Mn
x
quantum dots.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Using X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, atomic force microscopy, and Rutherford backscattering spectroscopy, the features of ...the microstructure and elemental composition of Si/GeMn magnetic systems obtained by molecular beam epitaxy and containing quantum dots are studied. Intense mixing of Ge and Si atoms is found in all samples. The degree of mixing (diffusion) correlates with the conditions of synthesis of Si/GeMn samples. For these systems, direct contacts of germanium atoms with manganese atoms are characterized and the presence of interstitial manganese with tetrahedral coordination and substitution of manganese for germanium and silicon in the lattice sites is found. The presence of stoichiometric phases Ge
8
Mn
11
, Ge
3
Mn
5
is not detected. The correlations of the Ge, Si, and Mn coordination numbers in the Ge environment are determined both with the Mn flux value (evaporator temperature) and with the temperature at which quantum dots are grown, as well as with other synthesis conditions. The manganese concentration in the samples is determined.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The microstructures of amorphous and polycrystalline ferroelectric Hf
0.5
Zr
0.5
O
2
films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film ...consists of an “incompletely mixed” solid solution of metallic oxides HfO
2
and ZrO
2
. After rapid thermal annealing, the mixed Hf
0.5
Zr
0.5
O
2
oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands are formed in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO
2
and ZrO
2
. The presence of the HfO
2
and ZrO
2
phases in the Hf
0.5
Zr
0.5
O
2
films is also detected by ellipsometry.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
XPS, Pb
L
3
and Cu
K
EXAFS, solid state NMR, and EPR techniques are used to study insoluble products formed in the interaction of aqueous solutions of lead(II) nitrate and copper (II) sulfate with ...potassium nbutylxanthate (KX). The XPS spectra of lead xanthates with the composition PbX
2
are similar to those of KX, and interatomic distances of 0.279 nm suggest a nearly ionic character of Pb–S bonds. In copper xanthate precipitating together with dixanthogen (approximately 15 wt.%), the Cu(I)–S bond length is smaller (0.229 nm), and copper coordination number of 2.9 in a composite with dixanthogen increases to 3.3 after its removal by washing with acetone. The XPS spectra indicate the covalent character of the bond and non-equivalence of xanthate radicals. Solid state
1
H and
13
C NMR spectra as well as the actual absence of metal lines under the measurement conditions demonstrate strong disordering of the structure of xanthates, which is stronger for PbX
2
and weakest in CuX after the removal of dixanthogen. EPR reveals sulfur-containing radicals and Cu
2+
in CuX, however, their amounts are insignificant and decrease after the washing with acetone. The results of the work are significant for the understanding of the reactivity of xanthates, in particular, under the conditions of flotation of base metal ores.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article presents the research data on the effect of Fusarium blight, Phoma rot, and Sclerotinia blight on the plant productivity of winter and spring rapeseed, brown mustard, and white mustard. ...As a result of studies, we found that Fusarium blight (the pathogens are fungi of the genus
Fusarium
Link) was the most harmful for the spring rapeseed, brown and white mustard – affection by it significantly decreased plant productivity. At 4 points of affection degree of plants, the harmfulness of the disease reached 71.2, 82.4, and 87.2 %, respectively. On winter rapeseed and mustard, plant productivity was considerably decreased by affection by Phoma rot in the form of a stem cancer (the pathogen is a fungus
Leptosphaeria maculans
(Desm.) Ces. et. De Not) and the stem form of Sclerotinia blight (the pathogen is a fungus
Sclerotinia sclerotiorum
(Lib.) De Bary.). The harmfulness of these diseases at 4 points of affection degree of plants reached 56.7 % and 66.7 % on rapeseed, and 56.6 % and 70.7 % on mustard, respectively.
This article deals with complex formation of Bi(III) with 3-mercaptopropanesulfonic acid (H
2
MPS) in aqueous perchloric acid solutions, with synthesis and characterization of a solid ...3-mercaptopropanesulfonate complex of bismuth(III). The stoichiometry and structures of Bi-MPS species in aqueous solution and of a solid complex have been studied by UV-Vis,
1
H-NMR, ICP-AES, Raman, and EXAFS spectroscopic methods; the structures have also been simulated with DFT/PBE0 calculations. The Bi(III) L
III
-edge EXAFS oscillation for a solid compound with the empirical formula Bi(HMPS)
2
(ClO
4
)
0
was simulated with two Bi-S interatomic distances at 2.50 ± 0.01 Å, two Bi-O distances at 2.56 ± 0.02 Å and two Bi-O distances at 2.75 ± 0.02 Å. Implementation of the same approach for aqueous solutions on the assumption of S
3
BiO
3
coordination at the H
2
MPS : Bi(III) mole ratio ≥ 3.0 revealed three Bi-S bonds at 2.53 ± 0.02 Å and three Bi-O bonds at 2.68 ± 0.02 Å, respectively. Optimized geometries, electronic structures of Bi(HMPS)
3
and Bi(HMPS)
2
ClO
4
0
, vibrational properties of Bi(HMPS)
2
ClO
4
0
, and electronic absorption spectrum of Bi(HMPS)
3
species obtained by DFT and TD-DFT modeling are consistent with empirical parameters. In the UV-Vis spectrum of Bi(HMPS)
3
the LMCT and MLCT S
2−
↔ Bi
3+
band appears at 268 nm.
Full text
Available for:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
III-nitride heterostructures in the form of multilayered quantum wells (MQWs) or quantum dots (QDs) and interacting Ge QDs ("quantum molecules") are promising candidates for high-speed intersubband ...(ISB) optical devices relying on the quantum confinement of electrons. Microstructural parameters (interatomic distances, coordination numbers, and Debye-Waller factors) were determined by means of EXAFS spectroscopy based on the Synchrotron Radiation, and the relationship between the variations in these parameters and the morphology of superlattices and symmetric assembles of QDs were established. The EXAFS technique has been used to study the local structure of thin hexagonal GaN AlN MQWs grown by ammonia MBE at different temperatures. It is shown that the heterointerface intermixing leads to a decrease in the Ga-Al interatomic distance and the Ga-Ga coordination number in MQWs. The degree of intermixing in the boundary layers rises from 30% to 40% with increase of the growth temperature from 795 to 895 °C. It was found that in the first phase of quantum molecules growth Ge atoms concentration is 25%. With further growth (deposition of the base layers) Ge concentration increases up to 35-45%, depending on the temperature (from 610 to 550 °C) of deposition.
Ge
K
edge EXAFS (Extended X-Ray Absorption Fine Structure) spectra have been measured for multilayer semiconducting heterosystems containing interacted groups of quantum dots (“molecules from quantum ...dots”) ordered in rings on different stages of their growth depending on topologic parameters and growth conditions. In accordance with our results obtained previously for the quantum dots of SiGe, for the molecules of quantum dots it was found that deformation at the interface leads to decrease in the interatomic distance of Ge–Ge by ~0.03 Å. Effect of heterosystem topology and temperature at different stages of their growth on interlayer diffusion was investigated. It was found that at the first growth stage (growth of “seeded islands” serving as a basis for obtaining the molecules) at 700°C a concentration of Ge atoms in the system is ~38%. With further growth of the vertically-matched quantum dots groups the concentration of Ge increases up to ~43-47% depending on the growth conditions. Comparable analysis of different modes of EXAFS measurements was performed to determine precisely structural parameters of heterosystem SiGe with different thickness grown on Si(100) surface.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper deals with complex formation of Bi( iii ) with 3-mercaptopropionic acid (H 2 MPA, H 2 L) in aqueous perchloric solutions. An extensive investigation on stoichiometry, stability and ...geometry of complex species in aqueous solutions and of solid HBi(MPA) 2 ·H 2 O complexes has been carried out by UV-Vis, 1 H-NMR, Raman, ICP-AES and EXAFS spectroscopic methods combined with ab initio research. All complex species have cyclic S,O-chelate structures. An ab initio simulation on the thermodynamics of complexation of Bi( iii ) by H 2 MPA has been carried out aiming to choose an appropriate quantum chemical methodology. The most accurate results have been achieved with M06 density functional, a SMD solvation model and the Def2-TZVPP basis set with discrepancies of stability constants within ± 1.0 logarithmic units.
Full text
Available for:
IJS, KILJ, NUK, UL, UM, UPUK
PDF
