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Peculiar features of the modification of Fe3O4 magnetic nanoparticles (MNPs) obtained by co-precipitation from solutions of FeII and FeIII salts (10-nm MNPs) and by the gas-condensation method (30-nm MNPs) with 3-aminopropylsilane and then with l-lysine were studied. The chemically obtained MNPs possess more pronounced hydrophilic properties and therefore readily form stable aqueous colloidal solutions and can be loaded with a larger amount of l-Lys. However, samples based on the physically obtained MNPs were characterized by more efficient internalization and longer retention times by the NIH 3T3 cells. The results obtained can be used in the design of novel nanomaterials for magnetic cell labeling.

Surface modification of magnetic nanoparticles (MNPs) with tetramethylorthosilicate and 3-aminopropyltrimethoxysilane was studied. The use of N-phosphonomethyliminodiacetic acid for the stabilization of the initial MNPs can significantly increase the coating thickness and specific surface area of SiO2/APS-modified (APS is 3-aminopropylsilane) MNPs. The possibility of sorption of antitumor drug doxorubicin (DOX) on the synthesized nanoparticles was studied. The degree of sorption of DOX increases with an increase in the specific surface area of the particles.

Magnetic iron nanoparticles (MNPs) encapsulated in a carbon shells and containing sulfo groups on the surface (Fe@C-SO3H) were synthesized. The aggregative stability of aqueous suspensions of the Fe@C-SO3H nanoparticles was studied in solutions of bovine serum albumin and calcium chloride and in phosphate-buffered saline, which simulate blood plasma. It is shown that the Fe@C-SO3H particles practically do not aggregate in the phosphate buffer saline for a long time (several days). On the contrary, MNPs encapsulated in a protein shells using ultrasonic treatment form aggregates up to 110–120 nm in size under these conditions. Suspensions of the Fe@C-SO3H particles are stable in aqueous solutions of calcium chloride in the range of the solid phase concentration between 0.05 and 0.10 g L−1. The results obtained indicate the possibility of using the functionalized Fe@C-SO3H nanoparticles in vitro experiments in biological media.

Nanopowders of the binary system of immiscible components Fe and Cu are synthesized by gas condensation of metal vapors. The structure and magnetic properties of nanopowders of various compositions are investigated, and their Mossbauer spectra are analyzed. It is shown that the method allows one to obtain nonequilibrium Fe(Cu) and Cu(Fe) solid solutions, in which the concentration of dissolved elements depends on the synthesis conditions.

Derivatives of RGD peptides are promising vector molecules for targeting biomolecules and nanoparticles into tumor tissues and are used for the design of diagnostic agents. The immobilization of the glutaryl-containing derivative of Gly-l-Arg(Pbf)-Gly-l-Asp(OMe)2 (GRGD) tetrapeptide on Fe3O4 magnetic nanoparticles (MNPs) was studied. The results of thermogravimetric and elemental analysis, as well as IR spectroscopy, were used to estimate the amount of organic components at each stage of modification of MNPs.

Using vacuum evaporation by a pulsed electron beam, mesoporous CaF2 nanopowders with a specific surface area of up to 91.5 m2/g were obtained. The effect of nanosecond electron beam irradiation in air on the magnetic and texture properties of the obtained nanopowders was studied. For the first time, the effect of irradiation on the specific surface and magnetization of CaF2 nanopowders was revealed.

The possibility of using the transverse relaxation time T2 of protons in aqueous media for quantitative measurement of the capture of magnetic nanoparticles by cells has been studied and demonstrated. The measurement of T2 was performed on a portable original NMR relaxometer with a measuring cell for a standard well of a biological plate. The novelty of the approach is that quantitative measurements of the capture kinetics were carried out using measurements of the proton relaxation time of the nutrient medium, which is determined by the remaining number of magnetic particles (not captured by the cells) in the medium. To study the kinetics of capture, two types of magnetic nanoparticles were synthesized: magnetite particles Fe3O4 and composite particles Fe@C with an iron-carbon shell structure. The surface of the particles was functionalized with amine-and carboxyl groups. The capture of aminated particles of Fe@C cells is established by microscopy and NMR-relaxometry by measuring the time T2. It is shown that the proposed method makes it possible to register very small concentrations of trapped magnetic nanoparticles equal to tens of pg/cell.

Mesoporous nanocrystalline CaF2 powder was produced by pulsed electron beam evaporation (PEBE) in vacuum. The specific surface area (SSA) of CaF2 nanopowder (NP) reached 88.7 m2/g. The effect of in-air thermal annealing in the temperature range of 200–900°C on the particle size, morphology, textural, thermal, magnetic, and luminescence properties of NPs is studied. A strong deviation from stoichiometry is observed in produced nanoparticles and a significant increase in the SSA after annealing at 200°C. The obtained CaF2 NP shows ferromagnetic (FM) behavior. The FM response appearance can be explained by the formation of structural and radiation defects. An analysis of pulsed cathodoluminescence (PCL) and magnetization curves of CaF2 NPs allows conclusions about their interrelation.

Nanoparticles Co3C were prepared using solid-phase synthesis under high pressure. The phase composition of the nanoparticles has been analyzed; the magnetization has been measured and 59Со NMR spectra in a local field have been recorded. It is shown that Co3C is a ferromagnet with the Curie temperature TC = 498(10) K. The hyperfine fields and components of electric field gradient tensor were determined for two nonequivalent Co positions in the carbide. The obtained hyperfine fields correspond to the spin state of Co ions S = 1.

The absorption spectra of cobalt-doped anatase TiO2 nanopowders in the infrared and visible ranges have been studied after various oxidative and reductive treatments. The annealing leads to the appearance of the Drude-like contribution in the infrared region and significant change in the absorption in an visible range due to the formation of defects of the oxygen-vacancy-type and Ti3+ ions. The observed additional contribution in the absorption spectra of TiO2:Co nanopowders as compared to the spectra of undoped powders is ascribed to the d–d transitions in ions Co2+. The change in the absorption related to cobalt after annealing is explained by a change in the local environment of Co ions from the octahedral to the tetrahedral environment.

Nanopowders Ni@C synthesized by gas condensation have a core-shell structure. The size of the core is 2–10 nm and the thickness of the shell is 1–3 nm. The changes in the magnetic properties and the structure of these particles upon annealing in the 100–1100°C temperature range are investigated in this work. Analysis of changes in the magnetic properties, the structure, and the chemical stability shows that the core of the particles in the initial state after synthesis is a supersaturated solid solution of carbon in nickel, which decomposes into nickel and carbon upon high-temperature annealing. Rather slow cooling of nickel particles causes the carbon shell to form. The shell ensures their chemical stability.

Core–shell CoFe@C and NiFe@C nanocomposites were prepared by gas-condensation synthesis. CoFe@C and NiFe@C particles had bcc and fcc cores, respectively. The treatment of these nanocomposites with hydrochloric acid revealed that they are more chemically stable than Fe@C composites. The maximum specific magnetization of CoFe@C and NiFe@C nanocomposites at room temperature in the field with a strength of 27 kOe was 125 and 58 G cm3/g, respectively. The processes of longitudinal and transverse relaxation of nuclear proton spins of aqueous suspensions of nanocomposites in various magnetic fields (0.5, 1, and 2 kOe) were studied. NiFe@C and CoFe@C nanocomposites have high transverse relaxivity values and can be used as magnetic markers for detection of low concentrations of bioobjects by NMR relaxometry.

Nanocrystalline TiO2 samples of various compositions (up to 5 at.% Fe) with anatase structure and an average particle size of about 20 nm were synthesized using sol-gel technology. The magnetic properties of nano-TiO2: Fe was studied by electron paramagnetic resonance (EPR) and Faraday balance. The existence of an inhomogeneous magnetic state in TiO2: Fe samples of different compositions were revealed by EPR spectroscopy in a wide temperature range. The analysis of the EPR spectra in the L -, X - and Q-bands allowed us to calculate the quadratic fine structure (D, E) parameters, “axial” and “rhombic” ones, respectively. The value of D turned out to be quite small, which indicates an insignificant anisotropy, which can be ignored describing the magnetic properties of TiO2:Fe. It was shown that the temperature behavior of different separate components of the integral EPR spectra can be qualitatively interpreted in the model of coexistence in the TiO2: Fe system, mainly, dimers with a strong negative exchange interaction and isolated paramagnetic centers. No ferromagnetic state in TiO2: Fe-based samples after etching of aE-prepared state were detected.

Mesoporous amorphous-crystalline nanopowders of BaF2 with the specific surface area up to 34.8 m2/g were obtained using evaporation by a pulsed electron beam in vacuum. Influence of the thermal annealing of the BaF2 nanoparticles in air at the temperatures from 200 to 900°C on the size and morphology of the particles and changes in their magnetic and luminescent properties was studied. The paramagnetic response of the BaF2 nanopowder was found to transform to the ferromagnetic response after annealing at 900°C. The appearance and transformation of the magnetic response in nanopowders made of BaF2, which is diamagnetic as the bulk material, are ascribed to the appearance of radiation-induced and structural defects during the synthesis process by pulsed electron-beam evaporation.

The method of pulsed electron beam evaporation in vacuum was first used to obtain CeF3 nanopowder (NP). During NP production, a high evaporation rate of the target (~ 7 g/h) and a higher percentage of NP collection (> 72%) were observed, both for fluoride and the previously obtained CeO2 oxide. It was found that the produced NP contains two crystalline phases: hexagonal CeF3 (95 wt.%, coherent scattering region ≈ 8 nm and [Ce-O-F] or [Ce-F]. The magnetic susceptibility of CeF3 nanoparticles (NPles) coincides with the susceptibility of micron particles, indicating the potential for using such NPles as a contrast agent for tomography. High specific surface area (CeO2-270 m2/g, CeF3 – 62 m2/g), large pore volume (0.35-0.11 cm3/g) allow the use of NPles as nanocontainers for drug delivery.

Various bismuth containing compounds are promising in many applications, including for creating photocatalysts based on them using a visible range of light. However, strong polymorphism (9 polymophic phases of Bi2O3), thermal instability and changes in the properties of bismuth oxide during long-term storage significantly complicate work with it. One way to increase stability and improve photocatalytic properties is by doping Bi2O3with various metals. Ag doped Bi2O3nanoparticles (NPs) are typically produced using chemical techniques often associated with the presence of toxic chemicals. The present paper used an environmentally friendly method of producing NPs using the method of pulsed electron beam evaporation in vacuum. The evaporation target was obtained by solid phase synthesis in an electric furnace on air using silver nitrate additives (1 and 5 wt.%). Textural, thermal and magnetic properties of the obtained NPs have been studied. Was found that the Ag-Bi2O3NPs have a specific surface area (SSA) of 23.7 m2/g, which was almost 2 times bigger than the SSA of the pure Bi2O3(13.2 m2/g) obtained previously. The thermal stability of the Ag-doped Bi2O3samples was maintained to the temperature 350°C. While further heating on air took place the phase transitionβ → α

Various magnetic nanopowders of iron oxide were obtained using the radiation-chemical method when irradiated with a nanosecond electron beam. The main physical and chemical characteristics of the prepared nanopowders were studied, such as structure, porosity, thermal resistance and magnetic properties. It was found that, by selecting precursors and the composition of the solution, it is possible to control not only the textural properties and yield of the obtained nanopowders (by changing the dose and dose rate intensity of the electron beam), but also to obtain crystalline or amorphous nanopowders, on which their magnetic properties depend. © 2021 Institute of Physics Publishing. All rights reserved. The reported study was funded by RFBR and GACR, project number 20-58-26002.

Nanoparticles with surface-modified shells are used for selective sorption of different impurities from water. Subsequent removal of nanoparticles from water can be strongly enhanced by using particles with magnetic core, providing their separation by sedimentation or filtration in magnetic field. The velocity of the magnetic sedimentation is strongly controlled by the particles aggregation which can be efficiently changed by interparticles interaction, in particular, by mixing the positively charged particles with negatively charged particles. The aggregation and sedimentation dynamics of the mixtures of the complex nanoparticles having the magnetite or the iron core, e.g., Fe 3 O 4 /SiO 2 , Fe 3 O 4 /SiO 2 NH 2 and Fe/C NH 2 in water were studied in a vertical gradient magnetic field B ≤ 0.3 T, dB/dz ≤ 0.13 T/cm. The sedimentation time t s was measured using two independent methods: by optically registered turbidity and from residual particle concentration in water by Nuclear Magnetic Resonance Relaxometry (NMRR) method. The t s reaches a minimum (7–10 min) for the (1:1) mixtures of the target Fe 3 O 4 /SiO 2 and the seed Fe 3 O 4 /SiO 2 NH 2 nanoparticles. Adding of the seed Fe/C NH 2 nanoparticles to the target Fe 3 O 4 /SiO 2 water suspension is more effective due to smaller sizes and to larger magnetic moments of the Fe-based particles. The sedimentation time of about (6−10) minutes is observed for rather small fraction (6, 15 mass%) of the added Fe/C NH 2 particles, which is important for application to reduce the residual sediment volume significantly. Preliminary exposure of the mixtures in the absence of magnetic field favors to more complete nanoparticles aggregation and, as a result, more rapid sedimentation of the nanoparticles in a vertical gradient magnetic field. The data obtained are useful for development of the methods aimed at magnetic separation of magnetic and nonmagnetic nanoparticles in water purification technologies.

The charge states of the cobalt ions in TiO2 nanopowders with the anatase lattice are studied by soft X-ray absorption spectroscopy. It is found that, at a low cobalt impurity concentration (1.8 at %), the cobalt ions with an oxidation state 2+ are mainly located in the tetrahedral (T d ) environment of oxygen ions. Amorphous titanium dioxide exists on the sample surface before heat treatment. Annealing in vacuum or hydrogen leads to the enrichment of the nanoparticle surfaces with Co2+ ions, a change in the coordination of the remaining part of cobalt ions from octahedral to tetrahedral, stabilization of the anatase structure, and the disappearance of the amorphous phase. The crystal lattice of the samples with a relatively high cobalt concentration (12 at %) is distorted, and annealing does not cause the disappearance of the amorphous phase of TiO2. Cobalt is reduced to its metallic state upon hydrogen annealing of the samples with a high cobalt concentration.

Radiative recombination with charge transfer was observed in NicMg1−cO (c = 0.008) oxides over the 8–300 K temperature range. This recombination occurs as a result of strong hybridization of the Ni2+ ion 3d-states and the band states. The charge transfer radiation excitation spectrum shows vibrational LO repeats of two exciton lines having charge transfer energy intervals of about 35 meV. The NiO nanocrystal absorption spectrum shows two weak peaks with energies of 3.510 and 3.543 eV, which are highly dependent on temperature. They are interpreted as charge transfer excitons at the edge of NiO fundamental absorption. The distance between the charge transfer exciton lines in the NicMg1−cO oxide spectra are caused by spin-orbit splitting of the valence band peak that was formed by the p-states of the oxygen ion.

The magnetic properties of an oxygen-deficient nanocrystalline undoped titanium dioxide synthesized by the gas-phase, electric-explosion, and chemical method have been studied. The defect state was controlled using reduction treatments in vacuum or in a hydrogen atmosphere. It is shown that the defect state of the surface of nanocrystalline oxides (for example, the existence of vacancies in the anion sublattice and other defects) has a dominant influence on the formation of the magnetic properties of the samples under study. The main contributions to the magnetism of TiO2 nanoparticles after the reduction treatments are the paramagnetic contribution of the matrix, the paramagnetic Curie–Weiss contribution, and the contribution of the spontaneous magnetic moment provided by the existence of regions with different spin ordering. A heterogeneous magnetic state is found to exist in the TiO2 nanopowders; for example, at low temperatures, shifted hysteresis loops are observed as a result of a possible set of magnetic states with different spin orders. It is shown that a soft compaction or grinding of nanopowders in an agate mortar lead to substantial increase in the magnetization, sometimes, by a factor of more than two, regardless of the nanopowder synthesis method and the initial phase state of TiO2 (anatase or rutile structures). This experimental fact proves the key role of the surface defects and the magnetic moment carriers with different spin configurations localized mainly on the nanoparticle surface. The compaction changes the magnetization only in the case when the initial magnetic state has a nonlinear “quasi-superparamagnetic” character of the magnetization curve. As a result of predominant exchange interaction between the nanoparticles with a frustrated character of spin ordering on the nanoparticles surface, the ferromagnetic contribution increases as nanoparticles contact.

The magnetization of a series of Al2O3 with different particle sizes and their 27Al NMR spectra have been studied at room temperature. The field dependence of the magnetization demonstrated the existence of a long-range ferromagnetic order in a small part of the sample at room temperature; however, the relative volume of this contribution was very small (less than 1%), and this seems likely due to an impurity phase. The NMR spectra did not contain any lines of metallic aluminum the existence of which in these nanooxides was assumed before in a surface layer of the nanoparticles, according to the data of other techniques. The data on the phase composition and the charge distribution in different phases of the Al2O3 nanoparticles have been obtained. The change in the mean particle size (by a factor of almost three) only insignificantly changed their phase composition.

Cobalt-doped anatase Ti1–xCoxO2 (0 < x ≤ 0.04) nanopowders (with a particle size of 30–40 nm) were produced by the hydrothermal synthesis method. Morphology, structure, and thermal stability of the synthesized compounds were examined using transmission electron microscopy, infrared spectroscopy, and X-ray diffraction analysis. Using X-ray photoelectron spectroscopy, cobalt ions are shown to have an oxidation state of 2+, with titanium ions having a tetravalent state of Ti4+. In the as-prepared state, all investigated compounds of Ti1–xCoxO2 are paramagnetic, with the value of paramagnetic susceptibility growing in proportion to cobalt content; with the spin of cobalt ion equal to S = 3/2. Analysis of the electron paramagnetic resonance spectra reveals that doping TiO2 with cobalt (up to 2%) is accompanied by a significant increase in the concentration of F+ centers. Further growth of the cobalt content results in a relatively wide line (nearly 600 Oe) in the spectrum, with a g-factor of about 2.005, demon...

The report is devoted to an analysis of the structural and magnetic state of the nanocrystalline diluted magnetic semiconductors based on TiO2 doped with Fe and Co atoms. Structural and magnetic characterization of samples was carried out using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR) spectroscopy, SQUID magnetometry, and the density functional theory (DFT) calculations. Analysis of the experimental data suggests the presence of non-interacting paramagnetic Fe3+ and Co2+ ions in the high-spin state and negative exchange interactions between them. The important conclusions is that the distribution of dopants in the TiO2 matrix, even at low concentrations of 3d-metal dopant (less than one percent), is not random, but the 3d ions localization and dimerization is observed both on the surface and in the nanoparticles core. Thus, in the paper the quantum mechanical model for describing the magnetic properties of TiO2:(Fe, Co) was suggested. The model operates only with two parameters: paramagnetic contribution of non-interacting 3d-ions and dimers having different exchange interactions between 3d magnetic carriers.

Mesoporous CaF2 nanopowders with the specific surface area up to 88.7 m2/g have been produced by the evaporation by a pulsed electron beam in vacuum. The influence of thermal annealing in air on the size and morphology of CaF2 nanoparticles and their magnetic, luminescence, and texture characteristics has been studied. Ferromagnetism of CaF2 nanopowders was discovered for the first time. The influence of radiation defects (CaF2 dye centers) on magnetic properties of CaF2 nanoparticles has been examined. © Published under licence by IOP Publishing Ltd. Russian Foundation for Basic Research, RFBR: 18-08-00514 This work was performed within the subject of the state task [0389-2015-0026]; was partial supported by the Russian Foundation for Basic Research [18-08-00514].

The 61Ni NMR spectra have been obtained in carbon encapsulated nickel nanoparticles. It has been shown that the cores of the particles consist of metallic nickel with face-centered cubic structure, nickel carbide Ni3C and carbon-nickel solid solution. The carbon shell of nanoparticles is a highly defective structure and close to an amorphous glassy-like carbon.

Mesoporous CaF2 nanopowders with specific surface area up to 91.5 m2/g have been obtained through evaporation by electron beam in vacuum. The effect of relativistic e-beam irradiation in air on magnetic and texture properties of CaF2 nanoparticles has been studied. The influence of annealing and irradiation on the specific surface area and magnetization of CaF2 nanopowder has been discovered for the first time. © Published under licence by IOP Publishing Ltd. Russian Foundation for Basic Research, RFBR: 18-08-00514 This work was performed within the subject of the state task [0389-2015-0026]; was partial supported by the Russian Foundation for Basic Research [18-08-00514].

The sedimentation dynamics of Fe3O4@SiO2 nanoparticles (20/30 nm) in water with additions of Na2SO4, CaCl2, NaH2PO4 salts with concentration of (5–100) mM were studied in a vertical gradient magnetic field (B1 ⩽ 0.3 T, dB/dz ⩽ 0.13 T/cm). The presence of magnetic field leads to nanoparticle sedimentation time decreasing from 103 h to 101 h and to 10−2 h when the salts are added. The results are interpreted on the basis of aggregate formation caused by electrostatic, steric and magnetic inter-particle interactions in water medium. While the stability of Fe3O4@SiO2 nanoparticles in pure water is dependent on steric inter-particle interactions involving polymeric Si–O groups on the surface of the composite particles, the presence of Na+ and Ca2+ cations in water leads to a decrease of electrostatic repulsion because the charge on the nanoparticle surfaces decreases. Magnetic moments, induced in the magnetic field, contribute to the enlargement of the aggregates and, in interacting with the magnetic field gradient, facilitates a quicker sedimentation of the suspension. The data obtained are useful for the development of methods aimed at the magnetic separation of magnetic nanosorbents in water purification technology.

Covalent immobilization of a pH-low insertion peptide (pHLIP) onto Fe3O4 magnetic nanoparticles was carried out resulting in the formation of MRI-visible materials able to specifically accumulate in acidic damaged tissue. The pH-dependent pHLIP-mediated binding of the obtained nanoconjugates to cells in acidic environment was demonstrated on HTC cells in vitro and in a mouse LLC tumour model in vivo.

Kinetic parameters of the process of thermal decomposition of the MgH2 hydride (obtained by the method of the mechanoactivation of magnesium in a hydrogen atmosphere) and of the commercial AlH3 hydride have been studied upon the rapid heating in the range of temperatures of 150–510°C at hydrogen pressures of 0–2 atm. The time dependences of the amount of hydrogen released by the metal hydrides at different temperatures and pressures have been determined. It has been shown that the activation energies of the hydrogen desorption are 135 kJ/mol for MgH2 and 107 kJ/mol for AlH3. The maximum rates of hydrogen desorption from the investigated metal hydrides have been established, and the temperatures and initial pressures that ensure the maximum rate and maximum volume of the hydrogen release have been determined.

The distribution of iron-carbon nanoparticles in FeC-DSPE-PEG-2000 modification (micellar particles with structure (Fe) core-carbon shell; PEG-based coating) is studied. The greater part of the nanoparticles accumulated in the spleen and liver, a small amount in the lungs, and the minimum amount in the thymus. The structural changes in the lymphoid organs were minor and involved only the microcirculatory bed. Analysis of the peripheral blood showed manifest anemia, thrombocytopenia, and leukocytosis.

Sedimentation dynamics of magnetite (γ-Fe3O4) nanopowders (10 - 20 nm) in water in the presence of a gradient magnetic field was studied by optical and Nuclear Magnetic Resonance (NMR) relaxometry methods. The magnetic field B ≤ 0.3 T, dB/dz ≤ 0.13 T/cm was produced by the system of permanent strip magnets. The initial sedimentation rate of the nanoparticles in water and under magnetic fields is higher for less concentrated suspensions (c0 = 0.1 g/l) than for more concentrated ones (c0 = 1 g/l). This might be connected with the formation of gel structures due to strong magnetic attraction between ferromagnetic nanoparticles. In the gravitation field, the suspensions of the particles (10 - 20 nm) remain stable for over 20 hours. The sedimentation process can be greatly accelerated by the action of a vertical gradient magnetic field, reducing the sedimentation time down to several minutes. In a gradient magnetic field enhanced by a steel grid, sedimentation of the nanopowder (c0 = 0.1 g/l) for 180 minutes resulted in reduction of the iron concentration in water down to 0.4 mg/l. In flowing water regime, the residual iron concentration in water 0.3 mg/l is reached after 80 minutes.

Me@C nanocomposites were prepared by evaporation of overheated liquid drop of Me in the flow of inert gas containing a hydrocarbon. The resulting carbon-coated nickel and iron nanoparticles contain metal cores of about 5 nm in size that are wrapped in a few layers of graphene-like carbon. Experimental data and theoretical results give evidence of the ability of carbon coating in nanocomposites Fe@C and Ni@C to H2 activation by dissociative adsorption due to the presence of space and structure defects and/or the presence of transition metal in subsurface layer. Since molecular hydrogen dissociation is the key step of hydrogenation reactions, both Ni@C and Fe@C provide high conversion of phenylacetylene (PA) (about 100%) during hydrogenation at the temperatures above 150 and 300 °C, respectively. Fe@C provides excellent styrene (ST) selectivity: 86% at 99% PA conversion at 300 °C. ST selectivity is moderate on Ni@C (about 60%) in the temperature range of 100–150 °С and low at higher temperatures.

TiO2-Co nanopowders were synthesized by the sol-gel method and gas condensation method. The structure of powders and its change during various heat treatments in air and hydrogen was investigated. The samples obtained by the gas condensation method contain ferromagnetic regions in the as-prepared state. This ferromagnetism does not disappear when annealed in air at 773 K. The magnetization curves of these powders are measured in the temperature range from 2 up to 773 K and the temperature dependence of the ferromagnetic contribution is analyzed.

The 61Ni, 13C NMR spectra of carbon encapsulated nickel nanoparticles have been obtained. It has been shown that the cores of the particles consist of metallic nickel with face-centered cubic structure, nickel carbide Ni3C and carbon-nickel solid solution. The carbon shell of nanoparticles is a highly defective structure and close to an amorphous glassy-like carbon. © Published under licence by IOP Publishing Ltd. Ural Branch, Russian Academy of Sciences, UB RAS: 18-10-2-37. The study was performed within the state assignments of the Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences: state program «Function» No АААА-А19-119012990095-0; state program «Magnit» No АААА-А18-118020290129-5 and state program «Alloys». The research also was supported by the project of the complex program of Ural Branch of Russian Academy of Sciences № 18-10-2-37.

Nickel-containing metal-carbon nanocomposites (Ni@C) synthesized by levitation melting in a flow of an inert gas-hydrocarbon mixture were used as catalysts of the hydrogenation of phenylacetylene (PA). The nanocomposites were characterized by X-ray photoelectron spectroscopy, simultaneous thermal analysis, and temperature-programmed reduction. The nickel-carbon nanocomposites were stable on storage in air, with only 13% of the total amount of nickel oxidized after 3.5 years of storage. In addition to nanoparticles completely covered with carbon, the composites contained partially coated metal particles, which are readily oxidized in air. Both types of particles exhibited the catalytic activity in phenylacetylene hydrogenation. At higher contents of nickel partially coated with carbon, the activity increased and the selectivity of styrene formation decreased. The minimum half-conversion temperature (75°C) was determined for a specially prepared Ni@C sample with an increased content of oxidized nickel (28%). The maximum selectivity of styrene formation (∼75% at 150°C) was recorded in the presence of the sample with the smallest amount of oxidized nickel (less than 4%).

Based on the combination of experimental measurements and first-principles calculations we report a novel carbon-based catalytic material and describe significant acceleration of the hydrogenation of magnesium at room temperature in the presence of nickel nanoparticles wrapped in multilayer graphene. The increase in rate of magnesium hydrogenation in contrast to a mix of graphite and nickel nanoparticles evidences intrinsic catalytic properties of the nanocomposites explored. The results from simulation demonstrate that doping of the metal substrate and the presence of Stone-Wales defects turn multilayer graphene from being chemically inert to chemically active. The role of the size of the nanoparticles and temperature are also discussed.

Fe3O4 magnetic nanoparticles (MNPs) were obtained using the gas condensation method. These MNPs were modified with 3-aminopropylsilane (APS) through covalent bonding. The methods of qualitative and quantitative analysis of the modified MNPs were developed using UV and IR spectroscopy and inductively coupled plasma emission spectrometry (ICP-ES). It was established that the maximum loading level of APS on the surface of Fe3O4 MNPs was 0.91 mmol/g MNP. The study of the activity of the surface amino groups of the nanocomposites was carried out by the example of their modification with (S)-naproxen. The optimum conditions for coupling reaction were found. It was shown that the reaction proceeded most efficiently when using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as coupling agent in the presence of 1-hydroxy-1H-benzotriazole (HOBt). The maximum immobilization level of (S)-naproxen on the Fe3O4 MNP surface was 0.55 mmol/g MNP. Thus, the high reactivity of amino groups of the obtained nano-composites was shown, making it possible to further modify them.

Using sol-gel synthesis and ion exchange, we have prepared titanium vanadium oxide nanopowders doped with transition-metal ions: M0.08Ti0.91V0.09O2 + δ · nH2O with M = Cr, Mn, Fe, Co, and Ni. The valence state of the ions in the nanopowders and their morphology and structure have been studied by scanning electron microscopy, X-ray diffraction, IR spectroscopy, and X-ray photoelectron spectroscopy. The M x Ti0.91V0.09O2 + δ · nH2O oxides dried in air or calcined at 400°C in air are shown to be paramagnets. Vacuum annealing of Co0.08Ti0.91V0.09O2 + δ · nH2O at 700°C gives rise to a significant ferromagnetic contribution.

59Co, 13C NMR spectra, magnetization and Raman spectra of Co@C nanoparticles encapsulated in carbon have been analyzed. It has been shown that the cores of the nanoparticles consist of metallic cobalt with FCC structure and perhaps the carbide of cobalt Co3C. Carbon shell have been characterized as a highly defective structure similar to amorphous or glassy-like carbon, however, it may include a small amount of the carbon nanotubes.

IR absorption and magnetic data for the titanium dioxide nanopowders are studied. Additional absorption in IR range is revealed in nanocrystalline TiO2 and Co-doped TiO2 after reducing annealing and explained by appearance of the oxygen vacancies and delocalised charge carriers. Increasing of the absorption in IR range after annealing of Co-doped TiO2 in vacuum (or decreasing of this contribution after annealing in air) correlates with arising (or vanishing) of ferromagnetic contribution. © 2018 The Authors, published by EDP Sciences. This work was supported by the Russian Scientific Foundation, Grant No. 16-12-10004.

Metal-carbon nanocomposites based on nickel, palladium, and iron and bimetallic palladium-nickel-carbon nanocomposites were for the first time used as catalysts of hydrodechlorination of chlorobenzene in the vapor phase in the atmosphere of hydrogen. Nickel and Pd-Ni nanoparticles completely coated by a carbon layer not only were stable to oxidation and agglomeration but also exhibited considerable activity in hydrodechlorination of chlorobenzene at temperatures much lower than those at which dechlorination on carbon carriers occurred. The dependence of catalytic properties (activity, selectivity, and stability) on temperature and nanocomposite composition was studied. Depending on the nature of the metal, the composition of bimetallic particles and temperature the selectivity could be changed, and the reaction could be directed toward the formation of benzene or cyclohexane. Carbon coating was stable under reaction conditions at least up to 350°C and did not hinder hydrodechlorination. Substrate adsorption likely occurred on the outside carbon surface of composite particles. The activity and structure of Ni@C composite remained almost unchanged after triple cycling over the temperature range from 50 to 350°C in a flow system.

Correction for ‘pHLIP-modified magnetic nanoparticles for targeting acidic diseased tissue’ by A. M. Demin et al., RSC Adv., 2016, 6, 60196–60199.