X-ray and electron spectroscopy investigation of the core-shell nanowires of ZnO:Mn

ZnO/ZnO:Mn core-shell nanowires were studied by means of X-ray absorption spectroscopy of the Mn K- and L_2,3-edges and electron energy loss spectroscopy of the O K-edge. The combination of conventional X-ray and nanofocused electron spectroscopies together with advanced theoretical analysis turned out to be fruitful for the clear identification of the Mn phase in the volume of the core-shell structures. Theoretical simulations of spectra, performed using the full-potential linear augmented plane wave approach, confirm that the shell of the nanowires, grown by the pulsed laser deposition method, is a real dilute magnetic semiconductor with Mn²⁺ atoms at the Zn sites, while the core is pure ZnO.     

Local surrounding of cobalt(II) in dithiocarbamate complexes,their magnetic and spectral properties

[Co(S₂CNRR’)₂] complexes [R = R’ = CH₃, C₂H₅, C₃H₇, C₄H₉, or CH₂C₆H₅; RR’ = (CH₂)₅, (CH₂)₆, or (CH₂)₂O(CH₂)₂] were prepared via interaction of CoCl₂ with sodium dithiocarbamates in aqueous medium (pH 6–7). [Co(S₂CNRR’)₂] are low-spin compounds (μ_eff 2.19–2.45 μ_B) with distorted square-planar geometry of the CoS₄ coordination node. The Co-S bonds length is 2.22–2.26 Å, and the distance between cobalt and carbon atoms is 2.73–2.74 Å.     

Identification of the Chromophore in the Apatite Pigment [Sr10(PO4)6(CuxOH1−x−y)2]: Linear OCuO− Featuring a Resonance Raman Effect,an Extreme Magnetic Anisotropy,and Slow Spin Relaxation

A new chromophore has been identified in copper‐doped apatite pigments having the general composition [Sr₁₀(PO₄)₆(Cu_xOH_1?x?y)₂], in which x=0.1, 0.3 and y=0.01–0.42. By using X‐ray absorption spectroscopy, low‐temperature magnetization measurements, and synchrotron X‐ray powder structure refinement, it has been shown that the oxygenated compounds contain simultaneously diamagnetic Cu¹⁺ and paramagnetic Cu³⁺ with S=1. Cu³⁺ is located at the same crystallographic position as Cu¹⁺, being linearly coordinated by two oxygen atoms and forming the OCuO^? anion. The Raman spectroscopy study of [A₁₀(PO₄)₆(Cu_xOH_1?x?y)₂,], in which A=Ca, Sr, Ba, reveals resonance bands at 651–656 cm^?1 assigned to the symmetric stretching vibration (ν₁) of OCuO^?. The strontium apatite pigment exhibits a strong paramagnetic anisotropy with an unprecedentedly large negative zero‐field splitting parameter (D) of ≈?400 cm^?1. The extreme magnetic anisotropy causes slow magnetization relaxation with relaxation times (τ) up to 0.3 s at T=2 K, which relates the compounds to single‐ion magnets. At low temperature, τ is limited by a spin quantum‐tunneling, whereas at high temperature a thermally activated relaxation prevails with U_eff≈48 cm^?1. Strong dependence of τ on the paramagnetic center concentration at low temperature suggests that the spin‐spin relaxation dominates in the spin quantum‐tunneling process. The compound is the first example of a d‐metal‐based single‐ion magnet with S=1, the smallest spin at which an energy barrier arises for the spin flipping.     

Electrochemical and chemical syntheses,structures, and optical properties of the zinc and cadmium complexes in the N,N,O,S-ligand environment

The chemical and electrochemical syntheses of the zinc (I) and cadmium (II) complexes are carried out on the basis of the tridentate Schiff base (H₂L), the condensation product of (2-tosylaminoaniline) N-(2-aminophenyl)-4-methylbenzenesulfunamide with 1-phenyl-3-methyl-4-formylpyrazole-5-thiol. The structures and compositions of the synthesized metallochelates are proved by the data of C, H, and N elemental analyses, IR spectroscopy, and ¹H NMR spectroscopy. X-ray absorption spectroscopy is used to determine the structure of the zinc complex. The binuclear structure of the cadmium complex is confirmed by the X-ray diffraction data (CIF file CCDC no. 1471159). The optical properties of H₂L and the zinc and cadmium complexes in dimethyl sulfoxide (DMSO) solutions are studied.     

Self-organizing cyclolinear methylcyclohexasiloxane polymers carrying reactive vinyl groups

Atactic cyclolinear organosilicon polymers containing vinyl substituents in RSiO_1.5, R₂SiO or both moieties have been synthesized through the heterofunctional polycondensation of trans,cis-2,8-dihydroxymethyl(vinyl)cyclohexasiloxanes with 2,8-dichloromethyl(vinyl)cyclohexasiloxanes. The structure of the polymers has been studied by ¹H and ²⁹Si NMR and IR spectroscopy, molecular mass measurements, and elemental analysis. The phase behavior of these copolymers in the bulk has been examined by DSC, X-ray diffraction, and polarization optical microscopy. It has been shown that the copolymer can exist in the mesomorphic state in the temperature range from ?100 to +200°C. The X-ray data indicate changes in the interlayer spacing and the type of packing of cyclolinear poly(methylvinylsiloxanes) with an increase in the content of vinyl substituents in the repeating units of the polymer. The ability of cyclolinear poly(methylvinylsiloxanes) to spread over the water/air interface and to form mono-and multilayers has been investigated. As the content of vinyl substituents in the polymer unit is increased to two or four, the ability of polymers to form multilayers is preserved. The incorporation of vinyl substituents into RSiO_1.5 or R₂SiO moieties of polymer units is accompanied by the formation of monolayers.     

Electrochemical synthesis,properties, and structure of copper,nickel, and cobalt complexes of tridentate tosylamino-functionalized mercaptopyrazole Schiff base

Copper, nickel, and cobalt complexes of the N,N,S-tridentate tosylamino-functionalized mercaptopyrazole Schiff base were obtained by an electrochemical method. The structure and composition of the metal chelates were characterized by C, H, N elemental analysis data and IR and ¹H NMR spectroscopy. More data on the structures of the complexes were obtained by magnetochemical and X-ray absorption spectroscopy measurements. The mononuclear structure of the copper(II) complex was confirmed by X-ray diffraction (CIF file CCDC no. 1473320).     

Ferrocene-containing tri- and tetranuclear cyclic copper(<Emphasis Type="SmallCaps">i</Emphasis>) and silver(<Emphasis Type="SmallCaps">i</Emphasis>) pyrazolates

New tri- and tetranuclear macrocyclic silver(i) and copper(i) 3-ferrocenyl-5-(trifluoromethyl)pyrazolates were prepared: [{(3-((η⁵-C₅H₄)Fe(η⁵-C₅H₅))-5-(CF₃)-Pz}M]₃ (M = Cu (1), Ag (2)) and [{(3-(( η⁵-C₅H₄)Fe(η⁵-C₅H₅))-5-(CF₃)-Pz}Cu]₄ (3). The structures of compounds were established by X-ray diffraction analysis. In the crystalline state, a planar trinuclear silver-containing macrocycliс pyrazolate and a saddle-shaped tetranuclear copper-containing macrocycle are formed. The introduction of a bulky substituent, ferrocene, into the pyrazole ligand results in complete shielding of the acidic metal sites, which precludes the coordination of base molecules.     

Investigation of PdZn nanoparticle formation upon the thermal decomposition of acetate precursors by in situ XRD and XAFS

The formation of metal or metal-oxide nanoparticles from four different precursor systems, including palladium(II) acetate, zinc(II) acetate, their 1: 1 mechanical mixture and the palladium-zinc bimetallic acetate complex PdZn(OCOMe)₄(H₂O), upon heating in a He + 5% H₂ atmosphere is studied using the X-ray diffraction and EXAFS (Extended X-ray absorption fine structure) techniques in the in situ mode. X-ray diffraction is primarily used to monitor changes in the phase composition of the samples. At specific moments when qualitative changes in the composition occur, EXAFS spectra at the K-edges of Pd and Zn are also measured. Using a combination of these two techniques, a detailed sequence of the phase transformations in each of the four precursor systems is revealed. It is found that the bimetallic acetate complex and the mixture of two monometallic acetates undergo chemical reduction to form zerovalent palladium under milder conditions than zinc acetate. However, the formation of a PdZn alloy from the mixture of metal acetates proceeds with a significant diffusion barrier.     

A structural study of biocompatible magnetic nanofluid with synchrotron radiation-based X-ray scattering techniques

In this paper, water colloidal solutions of nanoparticles of magnetite (magnetic nanofluids, (MNFs)) are investigated by synchrotron X-ray diffraction (XRD) and small-angle scattering (SAXS). To prevent aggregation, nanoparticles are coated with polyacrylic acid (PAA) in a single solution and citric (CA) in the other solutions. In both cases, the maxima of the particle size distribution from SAXS (9?C10 nm) correspond to the sizes of the magnetite crystallites that were estimated from the broadening of the diffraction lines. In addition, the SAXS data indicate the presence of a significant proportion of aggregates (up to 60 nm in diameter) in both colloidal solutions, although fundamental differences in the structures of aggregates between the MNFs stabilized by PAA and CA were not observed. In this study determination of the structural characteristics of MNFs were carried out in order to obtain stable dispersive non-aggregating nanoparticles of magnetite for use as contrast agents in magnetic resonance tomography, drug carriers, and other biomedical applications.     

Ni-Ge nanostructures: Role of the interface and the magnetic properties

The surface morphology and local structure of layers in the Ni-Ge and Ge-Ni-Ge-Ni-Ge films have been investigated. It has been shown that the surface of the films follows the roughnesses of the substrate surface, which have characteristic dimensions of 2–4 nm in height and ～100 nm in plane. It has been found that an interface with the depth ranging from 9 to 18 nm is formed at the boundaries between the Ni and Ge layers. The data obtained have been used to explain the specific features of the magnetic properties of the studied films, such as the asymmetry of hysteresis loops at low temperatures and the difference between the temperature dependences of the magnetization of the samples for two cooling modes: in a magnetic field and without a magnetic field.