Reactions of zinc and cadmium sulfates with 1,2-bis(pyridin-3-ylmethylene)hydrazine (3-bphz), 1,2-bis(pyridin-4-ylmethylene)hydrazine (4-bphz), and two methylated derivatives, ...1,2-bis(1-(pyridin-3-yl)ethylidene)hydrazine (3-bpmhz) and 1,2-bis(1-(pyridin-4-yl)ethylidene)hydrazine (4-bpmhz) resulted in eight coordination compounds. For Zn(II) the structural landscape includes binuclear complexes and two-dimensional coordination polymers, Zn2(3-bphz)(H2O)10(SO4)2.4H2O (1), Zn2(SO4)2(3-bphz)(H2O)4n (2), Zn2(3-bpmhz)3(H2O)8(SO4)2 (3), and {Zn(SO4)(4-bpmhz)(H2O)2.1.5(H2O)·0.25(4-bpmhz)}n (4). For Cd(II) two- and three-dimensional coordination networks, {Cd(SO4)(4-bpmhz)(H2O)1.32·1.2(H2O)}n (5), Cd(SO4)(3-bpmhz)(H2O)n (6), {Cd(SO4)(4-bphz)(H2O)·(H2O.C2H5OH)}n (7), and Cd3(SO4)3(3-bphz)3(H2O)2n (8) are reported. The extension of crystal structures up to two- and three-dimensional coordination networks has been achieved via bidentate bridging neutral azine ligands, and bi- and tridentate bridging sulfate anions that provide the metal-sulfate inorganic scaffolds in the forms of different one- and two-dimensional coordination arrays. The new crystalline solids were studied by X-ray single crystal and powder diffraction, spectroscopic and thermogravimetric analytical methods. The water-sulfate-anion interplay, similarities and dissimilarities in the coordination networks' topologies, the inherent chiralities of coordination networks, an impact of ligands’ methylation on solvent uptake, and the emission events accompanying the thermal stress are demonstrated and discussed.
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•Zn(II) and Cd(II) luminescent coordination polymers with four azine chromophores were prepared.•Structural diversity is attributed to the different structural features of the sulfate anions.•The Cd(II) 3D coordination grids demonstrate the highest thermal stabilities.•The luminescent properties are governed by the conformations of chromophores.•Three coordination polymers with methylated azine ligands form chiral crystals.
Evolution of coordination networks has been followed from the H-bonded supramolecular aggregates Zn2(3-bphz)(H2O)10(SO4)2.4H2O and Zn2(3-bpmhz)3(H2O)8(SO4)2 to the 2D and 3D coordination polymers, Zn2(SO4)2(3-bphz)(H2O)4n, {Zn(SO4)(4-bpmhz)(H2O)2 1.5(H2O)·0.25(4-bpmhz)}n, {Cd(SO4)(4-bpmhz)(H2O)1.32·1.2(H2O)}n, Cd(SO4)(3-bpmhz)(H2O)n, {Cd(SO4)(4-bphz)(H2O)·(H2O.C2H5OH)}n, and Cd3(SO4)3(3-bphz)3(H2O)2n. The dehydration results in the higher dimensionality of the infinite coordination motifs that demonstrate the diversity of metal-sulfate coordination scaffolds in the forms of single and ladder-type chains and two-dimensional sheets with different topologies.
The paper reports on the study of flow structure of a reacting propane-air jet, issued from contraction nozzle and impinged on flat metallic surface, by using the particle image velocimetry ...technique. Flows with different nozzle-to-surface distance H d were studied. The Reynolds number Re was in the range of 500÷5500, equivalence ratio Φ was varied from 0.8 to 1.4. Velocity field was measured for a conical premixed flame for Re = 1500 and Φ = 0.9. A region with flow recirculation was detected between the flame cone and the impingement surface for the case of H d = 4. This flow feature may result in a reduced local heat transfer.
The results of studying the effect of the silver nanoparticle concentration in TiO
2
–Ag functional coatings on the characteristics of GaInP/GaAs/Ge photoconverters are discussed. The optimum ...concentration of silver nanoparticles in TiO
2
coatings, improving the functional characteristics of solar cells is determined.
Integration of 2D semiconductors with photonic crystal slabs provides an attractive approach to achieving strong light–matter coupling and exciton–polariton formation in a chip-compatible geometry. ...However, for the development of practical devices, it is crucial that polariton excitations are easily tunable and exhibit a strong nonlinear response. Here we study neutral and charged exciton–polaritons in an electrostatically gated photonic crystal slab with an embedded monolayer semiconductor MoSe2 and experimentally demonstrate a novel approach to optical control based on polariton nonlinearity. We show that spatial modulation of the dielectric environment within the photonic crystal unit cell results in the formation of two distinct excitonic species with significantly different nonlinear responses of the corresponding charged exciton–polaritons under optical pumping. This behavior enables optical switching with ultrashort laser pulses and can be sensitively controlled via an electrostatic gate voltage. Our results open new avenues toward the development of active polaritonic devices in a compact chip-compatible implementation.
In this work, we analyze the role of a thin Cr spacer between Fe and Gd layers on the structure and magnetic properties of a Fe(35 Å)/Cr(
t
Cr
)/Gd(50 Å)/Cr(
t
Cr
)
12
superlattice. Samples without ...the Cr spacer (
t
Cr
= 0) and with a thin spacer (
t
Cr
= 4 Å) are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, static magnetometry, magneto-optical Kerr effect, and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4–300 K and analyzed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers.
Results of investigations of structural and magnetic properties of Fe/Cr/Gd superlattices that differ in the thicknesses of the Cr interlayer have been reported. The insertion of the Cr interlayer ...between Gd and Fe layers has been found to lead to structural changes in Gd layers and the appearance of an additional fcc phase in them along with the main hcp phase. The new fcc phase is uniformly distributed across the thickness of the layer and is not localized near layer boundaries or in the center of Gd layers. Polarized-neutron reflectometry was used to show that the aforementioned structural changes are accompanied by a substantial (two-fold to threefold) decrease in the average magnetization of gadolinium over a wide temperature range. Near interfaces of the Gd layer, a layer appears that is two-to-three monatomic layers thick and characterized by increased magnetic moment.
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