E. A. Eremina

Influence of boron-containing dopants on the formation of superconducting phase in the system Bi(Pb)-Sr-Ca-Cu-O

The effective dopants of , which formed phases compatible with the basic superconductor and did not cause the superconducting properties of Bi-2223 to deteriorate, was studied. It was found that the addition of 10 mol% of led to a reduction of the induction period and to an increase of the Bi-2223 phase content. It was shown that the surplus increased the amount of liquid in the system and thus accelerated the formation of Bi-2223 phase.

Physicochemical properties of fine-particle ZnFe2O4 prepared by spray pyrolysis of nitrate solutions

Fine zinc ferrite (ZnFe2O4) powders uniform in morphology have been prepared by spray pyrolysis of nitrate solutions. Examination by scanning electron microscopy showed that the powders consisted of micron- and submicron-sized polycrystalline spherical particles. The ZnFe2O4 sample prepared by pyrolysis at 1000°C had paramagnetic properties. Its crystal structure was refined by the Rietveld method and was shown to be a partially inverse spinel with a degree of inversion near 15%. According to nitrogen adsorption measurements, the specific surface of the powders was 5.2 m2/g. The electrical conductance of a film produced from fine-particle zinc ferrite was found to be very sensitive to the hydrogen sulfide concentration in air.

Langmuir hydrogen dissociation approach in radiolabeling carbon nanotubes and graphene oxide

Abstract Carbon-based nanomaterials have piqued the interest of several researchers. At the same time, radioactive labeling is a powerful tool for studying processes in different systems, including biological and organic; however, the introduction of radioactive isotopes into carbon-based nanomaterial remains a great challenge. We have used the Langmuir hydrogen dissociation method to introduce tritium in single-walled carbon nanotubes and graphene oxide. The technique allows us to achieve a specific radioactivity of 107 and 27 Ci/g for single-layer graphene oxide and single-walled carbon nanotubes, respectively. Based on the analysis of characteristic Raman modes at 1350 and 1580 cm−1, a minimal amount of structural changes to the nanomaterials due to radiolabeling was observed. The availability of a simple, nondestructive, and economic technique for the introduction of radiolabels to single-walled carbon nanotubes and graphene oxide will ultimately expand the applicability of these materials.

Synthesis of Nd0.7Ba0.3MnO3 via Microwave Processing

Nd0.7Ba0.3MnO3 is synthesized via microwave processing of neodymium, barium, and manganese nitrates in solution. It is shown that microwave processing allows the temperature and duration of Nd0.7Ba0.3MnO3 synthesis to be reduced as compared to the conventional ceramic route. The physicochemical properties of the resultant material compare well with those of samples prepared by ceramic processing techniques.

Investigation of kinetics of the process of formation of gold and silver nanoparticles and composites based on them

This article is devoted to studying the kinetics of formation of individual nanoparticles of noble metals and composites based on them. The effect of the concentration of the reducing agent and temperature on the rate of formation of nanoparticles of noble metals is studied. In order to characterize the morphology, phase composition, and optical properties of the synthesized nanomaterials, X-ray diffraction, transmission electron microscopy, UV–visible spectroscopy, and Raman scattering (RS) are used. It is shown that the formation of nanoparticles of noble metals and composites based on them is a three-step process consisting of an induction period, the process of nucleation, and the particle growth stage (which has an autocatalytic character). The formed nanoparticles of noble metals catalyze the further process of reduction of ions remaining in the solution. It has been confirmed that an important factor for amplifying the signal from the analyte molecules in Raman spectroscopy is the resonance absorption by nanoparticles of noble metals in a wavelength range close to the wavelength of the excitation laser.

Reduced graphite oxide decorated with gold nanoparticles for Raman scattering spectroscopy

Surface-enhanced Raman scattering (RS) spectroscopy is a sensitive analytical method that makes it possible to detect individual molecules. The substantial enhancement of the intensity of the signals in this method when compared to traditional Raman scattering is associated with two mechanisms, namely, electromagnetic and chemical. The first mechanism is associated with the enhancement of both the impinging and scattered radiation (electromagnetic enhancement), while the second mechanism is explained by the electron interaction between the molecule being analyzed and metal nanoparticles, namely, by the change in the polarizability of the adsorbed molecule, which results in the displacement and broadening of the electron levels of the adsorbed molecule or in the occurrence of new levels and promotes the enhancement of the signal in the Raman scattering spectrum. Graphene and material associated with it such as graphene oxide, graphite oxide, and reduced forms of graphene and graphite oxides are advanced materials for the creation of a significant chemical enhancement. Taking into account the different nature of the enhancement of the signal from the nanoparticles of noble metals and graphene and its derivatives, it is reasonable to study the effectiveness of hybrid structures on the basis of derivatives of graphene and noble metal nanoparticles in the Raman scattering spectroscopy of the analyte molecules with an aromatic structure.

The science Olympiad “Nanotechnology: Breakthrough into the Future”

The science Olympiad “Nanotechnology: Breakthrough into the Future,” a new educational program of the Moscow State University devoted to nanoscience, was described. The Olympiad combines the best traditions of Russian science Olympiads for schoolchildren with the new educational trends: research competitions for young scientists, creative contests for all participants, and a well-developed distant learning system. The Olympiad covers all the main branches of nanoscience and all the existing nanotechnologies. Examples of original problems on chemistry, physics, mathematics, and biology for schoolchildren were given. The new educational technologies used in the Olympiad, including distance learning techniques, were discussed. All the materials of the “Nanotechnology: Breakthrough into the Future” Olympiad are freely and openly available electronically.

Physicochemical Properties of R1 – xBaxMnO3 ± δ(R = Rare Earth) Solid Solutions

Nd1 – xBaxMnO3 ± δ(0.1 ≤ x≤ 0.5) and R0.7Ba0.3MnO3 ± δ(R = La, Pr, Sm, Eu) solid solutions were prepared from nitrate mixtures by solid-state reactions in air and were characterized by x-ray diffraction and thermogravimetry. The oxygen content of the solid solutions was determined by iodometric titration. The materials were found to have a nearly perfect oxygen stoichiometry (δ ≃ 0). As shown by pH measurements, the solid solutions have a high water resistance (extent of water degradation no larger than 0.1%). The dissociation of the Nd1 – xBaxMnO3 ± δ(0.2 ≤ x≤ 0.4) solid solutions was studied as a function of temperature and oxygen partial pressure (–10 ≤ log(Po2 /Pa) ≤ 1.4) by a special TG technique.

SNMS method for the analysis of bulk oxide ceramics and thin films

Publisher Summary The problem of quick and precise quantitative chemical analysis of solids is extremely complex and still not solved in many cases despite a wide variety of developed methods. Even more difficult are the questions that rise when thin films are considered. As post-ionization takes place in a gaseous state, the structure and composition of a sample analyzed cannot influence the extent of the ionization. Sputtered neutrals mass-spectrometry (SNMS) technique may be applied to a wide variety of objects, not only to conductive but also to insolating ones. A very important application of SNMS is depth profile analysis that may be used for studying of thin films and thin-film structures. Quick and precise quantitative analysis is possible. High depth resolution allows study of distributions of elements and isotopes in thin films.