In this work, we evaluated two synthetic approaches for the synthesis of M-ferrites nanoparticles, where M = Mn, Co, Zn with desired stoichiometric composition. As a starting point, thermal decomposition of acetylacetonates in benzyl alcohol and benzyl ether with oleic acid was chosen. Both of these approaches are widely used for the preparation of iron oxide nanoparticles; however, the synthesis of M-ferrites nanoparticles using these approaches is not well described. We have studied the influence of the nature of the solvent and surfactant on the quality of obtained ferrites (stoichiometric M:Fe ratio, structural phase analysis, morphology and core size of nanoparticles). It was shown that the chemical structure of solvent and presence of oleic acid plays a key role in controlling the nanoparticles stoichiometry. When benzyl alcohol was used as solvent, M-ferrites nanoparticles with diameters ranging from 3 to 5 nm were obtained, whereas of the benzyl ether with oleic acid resulted in formation of nanoparticles with diameters ranging from 7 to 9 nm. Moreover, only thermal decomposition of M acetylacetonates in benzyl alcohol was successful in obtaining M-ferrites nanoparticles with desired stoichiometry and high reproducibility M:Fe = 1:2 +/- 0.1). In addition, magnetic properties of obtained nanoparticles have been studied at room temperature and their dependence on M:Fe ratio (1:2, 1:6, 1:10) was shown. The results show a superparamagnetic behavior for all synthesized samples and high magnetization values from 19.7 to 99.3 A center dot m2 center dot kg  1. The maximum values of magnetization of M-ferrites samples are quite high for such small nanoparticles, which are closely related to their high crystallinity.

The effect of doping on the chemical and physical properties of semiconductors, alloys, ferroelectrics, glasses, and other substances has been a classic topic in materials science for centuries. Strontium titanate, SrTiO3, is an archetypal perovskite of interest for both fundamental science as quantum paraelectric and numerous outstanding physical properties and applications, including dielectrics, tunable microwave and photovoltaic devices, superconductors, thermoelectrics, potential multiferroics. Its chemical doping with transition metals leads to new functionalities, but intrinsic mechanisms of structural responses, activated by impurities, have not been systematically investigated. Herein, we present the results of a comparative study of the crystal structure, vibrational spectra, and dielectric properties of SrTiO3:M (M = Mn, Ni, and Fe, 2 at%) single crystals. It is shown that impurities constitute a different tendency to off-centering and the formation of dipoles: Mn and Fe atoms are shifted from the center of the oxygen octahedron, while Ni atoms remain on-centered. As a result, small chemical doping has a dramatic effect on the dielectric response through various structural mechanisms, including the pseudo Jahn-Teller effect, the first-order Jahn-Teller effect, and defect-induced distortion. These findings open up fundamentally new possibilities for the practical solution of a difficult problem: controlling the dielectric responses of quantum paraelectrics by choosing the type of chemical additive.

New anisotropic silicone magnetoactive composites were synthesized and studied. The surface structure and filler microdimensions in these elastomers were determined by electron microscopy. The atomic force microscopy use made it possible to determine significant surface deformations and magnetostrictive effects when small external magnetic fields are applied to the composites. Mössbauer spectroscopy on iron isotope nuclei made it possible to identify the fillers hyperfine parameters.

New anisotropic silicone magnetically active elastomers were synthesized and studied. Significant surface deformations and magnetostrictive effects in the obtained composites under the application of small external magnetic fields were visualized by the atomic force microscopy methods. This opens up the controlled wrinkling possibility for micro- and nanostructured surfaces. The use of nuclear gamma resonance made it possible to identify the iron filler electronic configuration in these anisotropic composites.

New anisotropic silicone magnetically active elastomers were synthesized and investigated by microscopy and spectroscopy. The record magnetostriction value in the obtained composites was determined by dynamic force microscopy, and their surface original wrinkled microstructure was visualized. The anisotropic elastomers surface topography changing by small external magnetic fields was found. Mössbauer spectroscopy use allowed determining the iron filler electronic configuration parameters in these composites. The obtained results were discussed and the conclusions about these materials prospects for practical applications were drawn.

Синтезированы и исследованы новые анизотропные силиконовые магнитоактивные композиты. Методом сканирующей электронной микроскопии определена структура поверхности и микроразмеры наполнителей из карбонильного железа этих эластомеров. Использование атомно-силовой микроскопии позволило определить значительные деформации поверхности и магнитострикционные эффекты при наложении небольших внешних магнитных полей на полученные композиты. Использование ядерного гамма резонанса позволило определить электронную конфигурацию железного наполнителя в этих анизотропных композитах.

Elastomeric silicone composites with ferromagnetic filler are investigated. The distribution of carbonyl iron filler in the polymer matrix by scanning electron microscopy is visualized. Using atomic force microscopy the magnetostrictive characteristics of these materials are established. 57Fe nuclei hyperfine parameters of the iron filler atoms in the composites are determined by Mössbauer spectroscopy. The influence of the filler microparticles restructuring in external magnetic fields on the composites properties is discussed. The prospects for creating new materials and devices based on the characteristics of such magnetically active elastomers are revealed.

An approach to the analysis of intracellular motion with nanosecond temporal resolution, based on the Mössbauer study of particles incorporated into a cell, has been developed. A possibility of applying magnetic nanoparticles as probes for studying in vitro the cytoplasm properties is analyzed. Two types of aqueous colloids of nanoparticles enriched with the 57Fe isotope are synthesized, and their cytotoxicity and biodegradation resistance under living cell conditions are investigated by an example of breast cancer cell line. It is found that the particles barely undergo any changes characteristic of biodegradation processes during their 120-h incubation in cells, although intracellular oxidation of divalent iron in the particle composition is observed. This result indicates possibility of using these particles for in vitro Mössbauer studies.

A mixture of iron carbides and fullerene C 60 formed by electric arc synthesis has been hydroxylated by adding OH groups to the fullerene surface, which made it possible, according to the EXAFS data, to obtain almost pure fullerenol Fe@C 60 (OH) 30 . Powder samples of the fullerenol and the product obtained after its dehydroxylation have been examined using Mössbauer spectroscopy. The Mössbauer spectra have been processed under the assumption of superposition of three partial doublets of spectral lines. It is established that two doublets due to Fe 3+ dominate in the fullerenol spectrum. For the reduced fullerene Fe@C 60 sample, two doublets are due to Fe 3+ and the Fe 2+ doublet dominates. Thus, attachment of OH groups from the outer side of the fullerene carbon frame increases the oxidation state of iron, which shows that the iron atom is located inside the frame.

The nonstandard nature of intracellular motion is associated with a considerable content of macromolecules and is largely due to the phenomenon of abnormal diffusion. Features of the motion of nanoparticles in concentrated protein solutions that simulate cytoplasm are studied on a nanosecond time scale by means of Mössbauer spectroscopy. A comparative analysis is performed of the nano- and macro-viscosity of the media.

In ensembles of single-domain magnetic nanoparticles, a magnetic-dipole interaction between particles takes place. The controlled assembly of bulk magnetically ordered materials from such nanoparticles opens up wide prospects for the creation of new magnetic materials. One of the classical methods for obtaining an ordered ensemble of nanoparticles is their synthesis in a matrix of clay minerals such as montmorillonite. The interlayer space of the mineral acts as a nanoreactor with specific conditions for the particle synthesis. Intercalating iron polycations into montmorillonite, one can obtain well-ordered ensembles of magnetic nanoparticles. Magnetic nanocomposites created in this way have new properties and exhibit non-standard magnetic behavior, which cannot always be described in terms of classical concepts. We used the capabilities of Mössbauer relaxation spectroscopy to study magnetic nanocomposites in order to study the structural and magnetic features of nanoparticles formed in aluminosilicate layers “from the inside”. An analysis of the Mössbauer spectra revealed that ordered ensembles of antiferromagnetic α-Fe 2 O 3 nanoparticles formed between aluminosilicate layers of montmorillonite exhibited ferromagnetic behavior.

The line broadening in the Mössbauer spectra of nanoparticles in model colloids with known viscosity has been studied. Magnetite nanoparticles with average hydrodynamic sizes of 140 and 40 nm and a set of stable aqueous colloids based on them have been synthesized. The nanoparticles have been enriched in the 57 Fe isotope to compensate for the significant decrease in the Mössbauer effect probability in liquid media. Two series of temperature experiments have been carried out: in an aqueous colloid of nanoparticles with a 90-% glycerol content and on dehydrated samples of nanoparticles in the absence of Brownian motion. It is established that the Brownian motion of nanoparticles causes an additional broadening of Mössbauer lines, which is inversely proportional to the viscosity and nanoparticle size. It is demonstrated that Mössbauer spectroscopy allows one to separate the contributions of the Brownian motion and the Néel relaxation of magnetic nanoparticles. It is confirmed that the shape of Mössbauer spectrum and the probability of Mössbauer effect depend strongly on both the size of particles suspended in a liquid and the dynamic viscosity coefficient of the liquid.

Biodegradation of nanoparticles includes the destruction of a stabilizing coating and the accompanying change in interparticle interaction, as well as the direct destruction of the inorganic nuclei of particles. These processes lead to characteristic changes in the shape of the Mossbauer spectra of iron oxide nanoparticles. In this work, we investigated the in vitro biodegradation of Fe-57-based magnetic nanoparticles with the aid of Mossbauer spectroscopy. For this purpose, two types of magnetic nanoparticles enriched with the Fe-57 isotope were synthesized. Copolymer Pluronic F-127 and citric acid were used to stabilize nanoparticles in aqueous medium. Moreover, synthesized nanoparticles were analyzed by physicochemical methods and investigated for cytotoxicity. The study of magnetic nanoparticles biodegradation was performed on 4T1 cell culture (breast cancer). We measured Mossbauer spectra of nanoparticles incubated with 4T1 cells and spectra of control nanoparticle samples at different conditions. The analysis of spectra was carried out in the many-state relaxation model formalism. The study revealed that after 120-hours incubation of nanoparticles in cells, they did not undergo measurable changes typical of biodegradation processes. Nevertheless, we noted intense intracellular oxidation of ferrous iron of synthesized nanoparticles to the ferric phase. The results obtained indicate the possibility of using the obtained nanoparticles in Mossbauer in vitro studies.

The theory and method for analysis of Mössbauer spectra of magnetic nanoparticles in a fluid have been developed by generalizing the model of the magnetic dynamics of a Néel ensemble of antiferromagnetic particles to the case of ferrimagnetic iron oxides. The resulting model describing the “superposition” of the magnetic dynamics and translational motion of nanoparticles in ferrofluids has been tested in application to the simultaneous analysis of Mössbauer spectra of “dry” magnetite nanoparticles and the same particles in glycerol.