Lusegen A Bugaev

Southern Federal University | sfedu · Department of Theoretical and Computational Physics

Borate glasses with a high content of lanthanum oxide are promising materials for the design of high refraction index optical media, although the fine tuning of their properties requires a detailed understanding of their atomic structure. We consider glasses of two systems: La2O3-xNb2O5-(1-x)B2O3 and La2O3-xTa2O5-(1-x)B2O3 with the refraction index...

Effect of single-doping by Ag2O (8 mol.%), Au2O (0.016 mol.%), Rb2O (8 mol.%), Nd2O3 (0.5 mol.%), Er2O3 (0.5 mol.%) on the structure and optical properties of zinc-phosphate (PZ) glasses was studied. Crystal-chemical similarity of local structures of the dopants in these glasses and in the revealed for them reference crystals of corresponding chemi...

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al2O3-S...

A method for representing data on the local structure of atoms in the form of histograms of paired radial distribution functions is proposed. This method is used to construct a structure descriptor needed to determine the structure of materials using machine learning and artificial intelligence techniques. A special feature of the method is the use...

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of a great interest for applications in photonics and optoelectronics. In the present study we explored the potential of generating the LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs) precipitated through the thermal treatment in ZnO-Al2O...

The effect of a small addition of CeO2 on the process of thermally stimulated formation of Au plasmonic nanoparticles in ZnO–MgO–Al2O3–SiO2 glass containing the crystallization catalysts TiO2 and ZrO2 was investigated by means of absorption spectroscopy, differential-scanning calorimetry, and X-ray diffraction analysis. It is shown that on heating...

Using absorption spectroscopy, differential scanning calorimetry, and X-ray powder diffraction, we studied the effect of a small addition of CeO2 on the process of thermally stimulated formation of plasmonic Au nanoparticles in the glass of the ZnO–MgO–Al2O3–SiO2 system containing TiO2 and ZrO2 as nucleating agents. It is shown that when the glass...

A study of the structural states of silver in glass after Ag+↔Na+ ion-exchange and further irradiation with different numbers of UV laser pulses has been performed using Ag K-edge XANES combined with DFT simulations and the processing of Ag K-EXAFS. Theoretical Ag K-edge XANES, calculated for DFT-generated structural models, showed high sensitivity...

We have obtained the X-ray total scattering patterns at wavelength 0.20735 ? and corresponding to them radial distribution functions (RDF) of electron density for glasses in the La2O3–Nb2O5–B2O3 and BaO–Nb2O5–P2O5 systems. The RDF demonstrate separate peaks at distances below ~1 nm which points on the middle range ordering in the considered glasses...

Bimetallic nanoparticles containing platinum and another d-metal are highly perspective catalysts with stability and activity superior to a single-metal platinum materials. It is known that the improvement of catalytic properties depends both from the composition and from the structural arrangement of atoms in bimetallic nanoparticles. This leads t...

Carbon encapsulated iron-cementite Fe-Fe3C nanoparticles with “core–shell” architecture, were synthesized by a single-step solid-state pyrolysis of iron phthalocyanine at the temperature 900 °C with pyrolysis time of 180 min. The morphology and size distribution of the fabricated nanocomposites have been investigated using high resolution transmiss...

High refractive glasses in the La2O3–Nb2O5–B2O3 (LNB) system were synthesized by the melt-quenching technique and correlations between their compositions and structural features were clarified. It was found that the refraction index of the LNB glasses is tunable from 1.71 to 1.98 by the variation of the Nb2O5 fraction from 5 to 30 mol.%. The infrar...

Gold nanoparticles precipitated in transparent glass-ceramics could pave the way for the development of multifunctional materials that are in demand in modern photonics and optics. In this work, we explored the effect of gold nanoparticles on the crystallization, microstructure, and optical properties of ZnO-MgO-Al2O3-SiO2 glass containing TiO2 and...

X-ray absorption near-edge structure (XANES) spectra are the fingerprint of the local atomic and electronic structures around the absorbing atom. However, the quantitative analysis of these spectra is not straightforward. Even with the most recent advances in this area, for a given spectrum, it is not clear a priori which structural parameters can...

Gold-doped glasses are of interest for plasmonics and photonics as optical media with well-resolved localized surface plasmon resonance (LSPR). We showed the possibility for the thermally-controlled tuning of the LSPR band position of gold nanoparticles precipitated in the ZnO-MgO-Al2O3-SiO2 glass nucleated by TiO2 and ZrO2 nucleators. The maximal...

The present study describes the synthesis of primary amines from long-chain fatty alcohols and ammonia using supported ruthenium catalysts over different acid supports, including a variety of zeolites with different topologies and Si/Al ratios. The morphology, acidity and location of ruthenium in the catalysts was studied in detail by combining XRD...

Plasmonic nanoparticles of gold, silver, their alloys, and of the promising magnesium and its alloys with noble metals, find increasing applications due to the valuable optical properties, based on the presence of localized surface plasmon resonance (LSPR) in the spectra of optical extinction. To suggest effective synthesis routes of such nanoparti...

Carbon-encapsulated iron-cementite (Fe-Fe3C) nanoparticles, promising nanomaterials for medicine due to their valuable magnetic properties, were synthesized by a single-step solid-state pyrolysis of iron phthalocyanine. To obtain required magnetic characteristics of such nanoparticles by governing of the pyrolysis conditions one needs reliable stru...

X-ray absorption near-edge spectroscopy (XANES) is becoming an extremely popular tool for material science thanks to the development of new synchrotron radiation light sources. It provides information about charge state and local geometry around atoms of interest in operando and extreme conditions. However, in contrast to X-ray diffraction, a quant...

Currently, much attention is paid to noble metal nanoparticles, which exhibit promising optical properties. These properties depend on many factors, including synthesis conditions, which raises interest to study the formation of such nanoparticles. In this work the results of research of silver ions stable local atomic structure, which were placed...

Effects of thermal post treatment and of thickness of the initial gold film coated the silicate glass surface, on localized surface plasmon resonance (SPR) of gold nanoparticles formed in glass by UV laser irradiation were studied to develop effective technique for production of gold nanoparticles and their arrays with required and stable character...

Optical extinction spectra calculated via multisphere T-matrices for nanoparticles with different concentrations of metals and different architectures (core–shell, inverse core–shell, or alloy) are considered. A method is proposed for determination of architecture of nanoparticles (core–shell or alloy) from only data on the position of plasmon reso...

Supported PtCu/C electrocatalysts containing core-shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu2+ and Pt (IV) in a carbon suspension, prepared on the basis of ethylene glycol–water solvent, and then treated at different temperatures in range from 250 to 350 °C. The structural characterization of “as pre...

Experimental technique for preparing of space arranged arrays of bimetallic AuAg nanoparticles in the near-surface region of glass, exhibiting surface plasmon resonance (SPR) characteristics varying in the wider ranges comparing to monometallic Au, Ag particles or corresponding thin films, is presented together with the structural characterization...

The mechanoactivation of ferroelectric materials with perovskite structure is performed. Structural changes of the ferroelectric materials after mechanoactivation based on X-ray absorption spectra (XAFS) and X-ray diffraction data (XRD) are studied. The Fourier analysis of EXAFS spectra allows quantitative estimates to be obtained for the local ato...

A method for synthesis of nickel nanoparticles in a magnetic nickel phthalocyanine anions matrix has been developed. The method is based on intercalation of potassium atoms to the nickel phthalocyanine (NiPc) polycrystalline powder at 300°C. The structure of (K2NiPc) was investigated by using high-resolution transmission electron microscopy (HRTEM)...

Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material e.g. in photo-catalysis), depend on how well we understand its fundamental properties. Among the ones that are either unknown or not kno...

Hydroxyapatite (HAp) is an important component of mammal bones and teeth, being widely used in prosthetic implants. Despite the importance of HAp in medicine, several promising applications involving this material e.g. in photo-catalysis), depend on how well we understand its fundamental properties. Among the ones that are either unknown or not kno...

Formation of localized surface plasmon resonance (SPR) spectrum of the randomly distributed gold nanoparticles in the surface layer of silicate float glass, generated and implanted by UV ArF-excimer laser irradiation of thin gold layer sputter coated on the glass surface, was studied by the T-matrix method, which enables taking into account particl...

Data for the vapor-phase doping (300°C) of nickel phthalocyanine (NiPc) by sodium taken in different concentrations (x), as well as structural analysis data for Nax = 0.2NiPc, Nax = 1NiPc, and Nax = 3NiPc samples, have been reported. The structure of the samples and their atomic configuration versus the doping level have been studied by transmissio...

PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu²⁺ and Pt(IV) in a carbon suspension prepared based on an aqueous ethylene glycol solution. The atomic structure of as-prepared PtCu nanoparticles and nanoparticles subjected to thermal treatment at 350°C was examined using PtL3 and CuK...

We report an in situ, temperature and H2 pressure-dependent, characterization of (2.6  0.4) nm palladium nanoparticles supported on active carbon during the process of hydride phase formation. For the first time the core-shell structure is highlighted in the single-component particles on the basis of a different atomic structure and electronic con...

Bimetallic platinum-copper nanoparticles on carbon support are studied as a perspective electrochemical catalyst by anomalous small-angle X-ray scattering near the Pt absorption L3-edge. The simultaneous fitting of several diffraction patterns measured at different photon energies lead to a satisfactory agreement between experimental and model curv...

Nanocatalysts PtCu/C with core-shell structure of PtCu nanoparticles were synthesized by the method of sequential chemical reduction of Cu²⁺ and Pt(IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of atomic structure of "as prepared" PtCu nanoparticles and obtained after thermal treatment at 350...

Depending on platinum loading and gas environment vastly different platinum structures in Pt/ceria were observed by Pt L3 -edge extended X-ray absorption (EXAFS) and X-ray absorption near-edge (XANES) spectroscopies. Calcination of highly loaded platinum (4 wt.%) yielded stacked layers of α-PtO2. The low platinum-loaded sample (2 wt.%), obtained by...

The results from developing and testing a software package for calculating the amplitudes and phases of electron scattering in polyatomic systems are presented. The potential with which an excited electron moves in a medium is constructed using the muffin-tin approximation with Hartree–Fock exchange interaction. Tests of the package for metals, oxi...

Composite metal-carbon electrocatalysts PtCu/C containing core-shell bimetallic PtCu nanoparticles were synthesized by sequential chemical reduction of Cu (II) and Pt (IV) in carbon suspension, prepared on the basis of ethylene glycol–water solvent. The characterization of “as prepared” and obtained after the acid treatment PtCu nanoparticles was p...

A new method for constructing three-dimensional models of bimetallic nanoparticles is proposed. This method, which is based on X-ray absorption spectroscopy data on the number and type of nearest neighbors, provides information on the distribution of types of atoms over the nanoparticle volume. The application of the method to the study of the stru...

A method based on doping of pure nickel phthalocyanine (NiPc) with a polycrystalline potassium powder at relatively low temperatures (300°C) has been proposed for the synthesis of a magnetic nanocomposite containing nickel nanoparticles stabilized in the NiPc matrix. The structural analysis of the synthesized nanoparticles and changes in the NiPc i...

Nanocatalysts PtCu/C with different distribution of components in bimetallic PtCu nanoparticles (NPs) were synthesized by simultaneous and sequential deposition of Cu and Pt on carbon support. Electrochemical stability of the obtained samples PtCu/C was studied using the cyclic voltammetry. Characterization of atomic structure of as prepared PtCu N...

Plasmonic Ag nanostructures were generated in glass surfaces by means of UV laser irradiation (193 nm). The aim of the work was to identify the correlations between the atomic structure of such nanoparticles and their optical properties. The structural characterization of the samples, prepared with different number of laser pulses was performed by...

In the current work we present a detailed analysis of the hydride phase formation in industrial Pd/C nanocatalysts by means of combined in situ X-ray absorption spectroscopy (EXAFS), X-ray diffraction (XRD) and volumetric measurements for the temperatures from - 10 to 50 °C in the hydrogen pressure range from 0 to 1000 mbar. α- and β- hydride phase...

Deposited electrocatalysts with different distributions of components in PtCu bimetallic nanoparticles involved in their composition were synthesized by simultaneous and sequential reduction of Cu(2+) and Pt(IV) in a carbon suspension. The dependence of the atomic structure of PtCu nanoparticles on the synthesis conditions and the degree of influen...

A Pd K-edge X-ray absorption near edge structure (XANES) analysis for palladium hydride and carbide nanoparticles is presented. It is shown that the presence of H and C atoms changes the Pd unoccupied p-electronic states, affecting the near-edge fine structure. Quantitative XANES analysis is performed using a multidimensional interpolation approach...

Nanocatalysts PtAg/C with different distributions of components in bimetallic PtAg nanoparticles were synthesized by the methods of simultaneous and sequential reduction of Ag+ and Pt(IV) in carbon suspension, prepared on the basis of ethylene glycol?water solvent. The characterization of atomic structure of as prepared PtAg nanoparticles and PtAg...

A technique for analyzing the extended X-ray absorption fine structure spectra of an atom in different structural states in a material under study is proposed. This technique makes it possible to determine the parameters of the nearest environment of absorbing atoms without applying Fourier filtering and related techniques. The proposed approach is...

Hydride formation in palladium nanoparticles was studied by Pd K-edge X-ray absorption spectroscopy in both the near-edge (XANES) and the extended (EXAFS) regions and by X-ray diffraction (XRD) both in situ as a function of temperature and hydrogen pressure. In contrast to EXAFS and XRD, which probe Pd–Pd interatomic distance changes, the direct ef...

Atomic structure of silver nanoparticles in soda-lime glass at T = 10 K before and after annealing was studied by Ag K-edge EXAFS. To overcome ambiguities in the structure determination by the Fourier-transform analysis of these spectra, caused by the presence of various species of the absorbing silver atoms in the sample, the refinements of the fi...

The local atomic structure of Ni in nickel phthalocyanine was studied by K-edge X-ray absorption fine structure spectroscopy. The obtained inter atomic nickel-nitrogen distance differs from the reference X-ray diffraction data so an additional study was performed within density functional theory framework. The justification of the used theoretical...

The effects of hydrogen in Pd nanoparticles on the features of Pd K-edge X-ray absorption near edge structure (XANES) are studied. Simulations indicate a linear dependence of the intensities of XANES maxima upon the concentration of hydrogen in the bulk of Pd clusters at low H-concentrations and stepwise increase of the first near edge peak at high...

The electronic structure of the filled and unfilled states and the formation of the chemical bonding in PtO2, PtCl4, PtS2, and Au2S are studied by measured Pt and Au Lβ5 X-ray emission spectra (XES) and L3-edge X-ray absorption spectra (XAS). The study is based on the comparative analysis of the calculated local partial densities of electronic stat...

By using solid-phase pyrolysis of copper phthalocyanine we have prepared copper nanoparticles in carbon matrices. The elemental composition, structure, and morphology of nanocomposites were investigated by scanning electron microscopy, energy dispersive X-ray microanalysis, and X-ray diffraction. Depending on the temperature and time of pyrolysis,...

By using a modified method of solid-phase pyrolysis of metal-phthalocyanines, we have synthe-sized ferromagnetic Ni nanoparticles in different carbon structures: amorphous carbon plates, multiwall carbon nanotubes, carbon fibers, and graphitized capsules. The composition, structure and morphology of prepared composite materials have been studied by...

By using a modified method of solid-phase pyrolysis of metal-phthalocyanines, we have synthe-sized ferromagnetic Ni nanoparticles in different carbon structures: amorphous carbon plates, multiwall carbon nanotubes, carbon fibers, and graphitized capsules. The composition, structure and morphology of prepared composite materials have been studied by...

Ab initio modeling is used to analyze the specific near-edge features of the X-ray absorption K spectra of ∼3-nm cobalt nanoparticles. It is established that the observed differences between the spectra of the nanoparticles and those of bulk cobalt samples are due to contribution from atoms of the nanoparticles’ surface layer, the local environment...

By using the solid-phase pyrolysis of phthalocyanines the nickel-carbon nanocomposites have been synthesized. The composition, structure, and morphology of samples were investigated by scanning electron microscopy and Raman spectroscopy. The first-order Raman shifts of prepared materials were measured with laser excitation at 514.5 nm in the freque...

Applicability of the existing criteria for signal frequencies resolution to the problem of close interatomic distances determination by energy-restricted x-ray absorption spectra is studied within the approach based on the Fourier transformation and fitting procedures. Without losing generality, theoretical signals k of different k dependencies are...

Experimental Si K edge X-ray absorption near-edge fine structure (XANES) of zeolite faujasite, mordenite, and beta are interpreted by means of the FEFF8 code, replacing the theoretical atomic background mu(0) by a background that was extracted from an experimental spectrum. To some extent, this diminished the effect of the inaccuracy introduced by...

Based on the example of signals with a known form of functional dependence, as is the case in X-ray absorption spectroscopy (XAS), the applicability of the available general estimates of the frequency resolution limits in the case of determining two close interatomic distances by a Fourier analysis of short energy range XAS spectra is considered. A...

A technique for determining the factorized atomic part sigmaat( k) of the X-ray absorption cross section in the near-edge range of small photoelectron wave numbers k, based on the selection of this function from the experimental absorption spectrum of the atom in a compound, has been developed. This technique has been tested using the X-ray absorpt...

Local structural distortions in Indium Arsenide at 11 GPa are studied applying the Fourier-transform analysis to As K-edge XAFS restricted to a short exploitable energy range of ~ 250 eV above the edge, due to the Bragg reflections from the diamond anvils. The best model for the distribution of In-atoms around As is obtained by combining available...

An algorithm and code for the determination of the factorized atomic part of the absorption cross-section from experimental spectra in the XANES region were generated and tested on Al and Si K-edge XANES in reference compounds and applied to zeolite Beta with various Si/Al ratios. However, replacement of the theoretically determined background with...