Abstract
The comprehensive study of the electronic density distribution of CuCr
0.99
Ln
0.01
S
2
(Ln = La, Ce) solid solutions was carried out using both X-ray photoelectron and emission ...spectroscopy. It was found that cationic substitution of chromium with lanthanum or cerium atoms does not significantly affect the atomic charges of the matrix elements (Cu, Cr, S) in the lanthanide-doped solid solutions. The copper atoms in the composition of CuCrS
2
-matrix and the lanthanide-doped solid solutions were found to be in the monovalent state. The chromium and lanthanide atoms were found to be in the trivalent state. This fact indicates the isovalent cationic substitution character. The sulfur atoms were found to be in the divalent state. The near-surface layers contain the additional oxidation forms of sulfur (S
0
, S
4+
,
S
6+
) and copper (Cu
2+
) atoms. The detailed analysis of the valence band structure using DFT calculations has shown that partial DOS distribution character of the matrix elements is preserved after the cationic substitution. The experimental valence band spectra structure of CuCrS
2
-matrix and CuCr
0.99
Ln
0.01
S
2
is determined by the occupied copper
d
-states contribution. The contribution of the lanthanide states in the valence band structure is lower in comparison with those for the matrix elements. The major contribution of the lanthanide states was found to be mainly localized near the conduction band bottom.
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A comprehensive study of the thermoelectric properties of CuCr0.99Ln0.01S2 (Ln = La…Lu) disulfides was carried out in a temperature range of 300 to 740 K. The temperature dependencies of the Seebeck ...coefficient, electrical resistivity, and thermal conductivity were analyzed. It was found that the cationic substitution of chromium with lanthanides in the crystal structure of layered copper–chromium disulfide, CuCrS2 resulted in notable changes in the thermoelectric performance of CuCr0.99Ln0.01S2. The cationic substitution led to an increase in the Seebeck coefficient and electrical resistivity and a thermal conductivity decrease. The highest values of the thermoelectric figure of merit and power factor corresponded to the praseodymium-doped sample and an initial CuCrS2-matrix at 700–740 K. The cationic substitution with lanthanum, cerium, praseodymium, samarium, and terbium allowed for an enhancement of the thermoelectric performance of the initial matrix at a temperature range below 600 K. The cationic substitution of CuCrS2 with lanthanum and praseodymium ions appeared to be the most promising approach for increasing the thermoelectric performance of the initial matrix.
The electronic structure of heterometallic cubane-type clusters with core {Mo
3
S
4
M′} (M′ = Cu
+
, Ni
0
, Pd
0
) was investigated by the Atoms in Molecules and Electron Localization Function ...topological methods as well as Energy Decomposition Analysis. It was found that {Mo
3
S
4
Cu} and {Mo
3
S
4
M′} (M′= Ni, Pd) clusters have a different interaction between molybdenum and heterometallic atoms. In case of the complexes with Ni/Pd atom, the disynaptic basins on the Mo–M′ bonds were observed in contrast to the Cu containing complex. The complex formation between heterometallic fragments and trinuclear molybdenum complex {Mo
3
S
4
} were found to be hindered due to steric interactions. Nevertheless, the formation of the heterometallic cubane-type clusters occurs due to the multicenter and pair covalent interactions between Mo and M′ atoms.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•The new polyol sol–gel method for synthesis of new Y2O3@SmS compound with a core–shell nanostructure was reported for the first time.•It was found to be a promising value of Seebeck ...coefficient in comparison with other thermoelectric materials based on the rare earth elements.•The obtained results demonstrated the correlation between the Seebeck coefficient, the real structure and the internal microstructure changes for Y2O3@SmS composite.•The composites based on both the rare earth monosulfide and oxide were considered as a promising thermoelectric materials.
The Y2O3@SmS composite with a core–shell nanostructure was synthesized using the polyol sol–gel method. For the first time the oxide powder Y2O3@Sm2O3 precursor was obtained from Y2O3 and Sm(acac)3 solutions in diatomic alcohol ethylene glycol C2H4(OH)2 by the precipitation of urea (NH2)2CO. Next, the precursor was heated to 633 K in the sulfidation atmosphere and annealed at 1423 K to obtain the final Y2O3@SmS composite. It was found that Y2O3@SmS compound contains a small amount of Sm2S3 impurity phase due to the diffusion process of the sulfur atoms of SmS2 phase to the sample surface, followed by a transition of SmS2 to Sm2S3 phase. The short-range order was analyzed using both Raman and XPS spectroscopy. The obtained data showed that Y2O3@SmS composite has a core–shell structure. Y2O3 phase was considered as a core, and the SmS phase – as the shell. Using the SEM and HRTEM data it was found that synthesized sample contained a significant amount of the core–shell nanoparticles with the average size of ∼ 200 nm. The Seebeck coefficient was of –40 µV/K at 430 K. The obtained value was two times greater compared to SmS@Y2O2S and Y2O2S@SmS core–shell compounds studied previously.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The comprehensive study of the lanthanide-doped solid solutions CuCr0.99Ln0.01S2 (Ln = La…Lu) magnetic properties was carried out using static magnetochemistry and differential scanning calorimetry ...techniques. It was shown that magnetic properties of CuCr0.99Ln0.01S2 are significantly affected by the magnetic properties of the lanthanide ion. The magnetic susceptibility and the effective magnetic moment were found to deviate from the Curie-Weiss law in the temperature 90 K below and 50 K above the order-disorder transition at 695 K. The observed behavior of the temperature dependence of the effective magnetic moment in the order-disorder transition temperature region was described as a result of copper atoms redistribution over different types of the crystallographic sites.
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A comprehensive study of the valence state and the local coordination character of Mn1−xYbxS (x = 0; 0.01; 0.05) solid solutions has been performed using X-ray absorption spectroscopy combined with ...finite difference method calculations. The good agreement between experimental and calculated data indicates that cationic substitution does not lead to significant changes in the manganese local coordination character. The ytterbium atoms are found to be in the trivalent state, while the manganese and sulfur atoms are in the divalent state.
According to the experimental and calculated data, the ytterbium atoms are in the trivalent state, the manganese and sulfur atoms are in divalent state in the cation-substituted solid solutions Mn1−xYbxS (x = 0; 0.01; 0.05). Display omitted
•Charge state studies of Mn1−xYbxS performed using XANES, XES and quantum chemistry.•The Yb atoms are in the trivalent state, the Mn and S atoms are in divalent state.•The Mn → Yb substitution does not changes the local environment structure of Mn.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•A way to obtain conductive silver films is proposed.•Conductive silver films were formed by the Doctor Blade method.•Janus membrane based on conductive silver film was ...obtained.•Obtained membrane is a promising material for flexible microelectronics.
The organasol of nanoparticles (3 M, the particle size 6 ± 1 nm) was synthesized by the silver nitrate reduction with hydrazine in the reverse emulsions stabilized by the sodium bis(2-ethylhexyl)sulfosuccinate. The obtained silver nanoparticle emulsion was concentrated using electrophoretic concentration. The silver nanoparticle films with tunable thickness (from 3.9 ± 0.2 to 1.7 ± 0.2 µm), porosity (from 26 ± 10 to 46 ± 12%), density (from 5.7 ± 1.5 to 7.8 ± 3.0 g/cm3), roughness (from 4 ± 2 to 131 ± 19 nm) and surface electrical resistivity (from 0.03 ± 0.01 to 0.10 ± 0.01 Ohm/□) were obtained. The sintering process of the silver nanoparticle films was studied by in situ XRD experiment using synchrotron radiation. The separation procedure for the metallic films from the solid substrates was proposed. The separated sintered silver nanoparticle film was considered as a Janus membrane. The wetting asymmetry of the obtained Janus membrane was of 39°. The obtained films were considered as promising functional material with the bactericidal and the electrical conductive properties. The obtained Janus membrane could be placed on the flexible polymer substrates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•eElectronic structure and stability of hexanuclear complex with β-diketonate ligands.•DFT calculations and NBO analysis for the electronic structure of hexanuclear complex.•Investigation of the ...charge distribution by XPS techniques.
Interatomic interactions and charge state of atoms in hexanuclear complex Cu6(hfa)4(dpm)4(OH)4 have been studied by the methods of quantum chemistry and X-ray photoelectron spectroscopy (XPS). The shape and energy position of the Cu2p3/2-lines indicate that all copper atoms state could be interpreted as Cu2+. It was also analyzed the quantum chemical and XPS data on atomic charge distribution for monoligandic bis-β-diketonate Cu(hfa)2 and Cu(dpm)2 complexes. The comparison of calculated and experimental data for monoligandic and hexanuclear complexes revealed the electronic density redistribution on the oxygen and copper atoms in 1 due to the charge transfer interaction between Cu(hfa)2- and Cu(dpm)-fragments with participation of the bridging OH-groups, which was confirmed by NBO analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The work reports a comprehensive study of the Seebeck coefficient, electrical resistivity and heat capacity of CuCrS2 in a wide temperature range of 100–740 K. It was shown that the value of the ...Seebeck coefficient is significantly affected by the sample treatment procedure. The order-to-disorder (ODT) phase transition was found to cause a metal-insulator transition (MIT). It was established that the ODT diminishes the Seebeck coefficient at high temperatures (T > 700 K). The DFT calculations of the CuCrS2 electronic structure showed that the localization of copper atoms in octahedral sites makes the band gap vanish due to the MIT. The decrease of CuCrS2 electrical resistivity in the ODT temperature region corresponds to the MIT.
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The chemistry of transition metal clusters has been intensively developed in the last decades, leading to the preparation of a number of compounds with promising and practically useful properties. In ...this context, the present work demonstrates the preparation and study of the reactivity, i.e., the possibility of varying the ligand environment, of new square pyramidal molybdenum chalcogenide clusters {Mo5(μ3-S)i4(μ4-S)i(μ-pz)i4}(pzH)t51+/2+ (pzH = pyrazole, i = inner, t = terminal). The one-step synthesis starting from the octahedral Mo6Br12 cluster as well as the substitution of the apical pyrazole ligand or the selective bromination of the inner pyrazolate ligands were demonstrated. All the obtained compounds were characterized in detail using a series of physicochemical methods both in solid state (X-ray diffraction analysis, etc.) and in solution (nuclear magnetic resonance spectroscopy, mass spectrometry, etc.). In this work, redox properties and absorption in the ultraviolet-visible and near-infrared region of the obtained compounds were studied.
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