Vol 12, No 5-6 (2017)

The identification of subtle structural effects in bimetallic nanoparticles via conventional methods is discussed using the example of PtCu/C nanostructured electrocatalysts. The divergence factors between experimental X-ray diffraction profiles and patterns simulated in the single-phase approximation for pure (or solid solution) and bi-phase metals in a suspected core–shell structure are found to be different. The catalysts containing the core–shell nanoparticles may be chosen from some materials with nanoparticles of different architectures based on X-ray diffraction and cyclic voltammetry data if the nanoparticles consist of a relatively massive Cu core and a thick Pt shell.

In the last decades, extensive research has been undertaken to find solid electrolytes that might increase the power and safety of promising electrochemical devices such as lithium batteries, supercapacitors, and solid oxide fuel cells. It is mainly based on the screening of advanced functional suprastructures and developing special synthesis procedures to obtain nanosized materials, allowing one to increase ionic conductivity. That’s why special attention is paid to composite solid electrolytes. In this work we use the accumulated knowledge on the physical chemistry of metals and alloys to describe the amorphization effects. It is known that amorphization at the interphase boundaries (interfaces) and grain boundaries noticeably increases (sometimes by orders of magnitude) the ionic transfer rate and, therefore, affects the functional properties of nanostructured composite solid electrolytes. In the theoretical model proposed, we have attempted to elucidate the reasons, inducing the amorphization effects which are observed upon the crystallization of inorganic eutectics and composite formation. We have especially used the approximation of rigid discs, considered, unit-cell volumes. In the context of the theory, describing the amorphization as an excess molar volume arising upon the crystallization of metals and alloys, we have established that the degree of amorphization depends not only on the synthesis conditions, but also on the incommensurability of crystal unit cells in the components. The findings can be useful in the elaboration of novel inorganic materials for various applications.

The influence of the interaction between n-ZrO₂ and n-Al₂O₃ on their radiation and catalytic activities in the process of hydrogen production from water is investigated. It is established that, as a result of the interaction between n-ZrO₂ and n-Al₂O₃, the new phase n-ZrO₂–n-Al₂O₃ is formed, which leads to the reduction of radiation and catalytic activity in comparison with separate components and the additive sum of their activities. Regularities of dependences of radiation and catalytic activity from the maintenance of components of the n-ZrO₂–n-Al₂O₃ system are received in the process of hydrogen production. Mechanisms of processes of energy transfer and transmission in the studied nanodimensional systems are offered.

The photocatalytic activity of nanosized titanium dioxide powders synthesized by thermal treatment of the precursor phases precipitated from aqueous solutions on the degradation of methylene blue in a solution under the action of UV radiation has been studied. The dependence of the photocatalytic activity on pH of the medium used to precipitate precursor phases in combination with temperatures and duration of their thermal treatment has been found. The selected synthesis conditions allowed to obtain titanium dioxide materials that appear to be at least two times more active than the commercial catalyst Degussa P25. It is found that the materials based on anatase modification of titanium dioxide obtained from the phases precipitated at pH 7–9 and calcined at 600°C for 1–2 h show the highest photocatalytic activity. It is shown that under UV radiation 25 min is enough for almost complete destruction of methylene blue dye in the solution with an initial concentration of 20 mg/L.

A new analytical solution of the Helmholtz equation in spherical coordinates for an infinite homogeneous space, as well as the solution of the boundary problem for a piecewise-homogeneous medium (space divided into homogeneous domains with various dielectric permittivities of the spherical symmetry borders) has been obtained. The application of the derived formulas to spherical nanoparticles of metal makes it possible to record a mathematical relation to the localized plasmon resonance, which connects the resonance parameters of such a system and the electromagnetic waves. The equation of plasmon resonance confirms the known experimental result of significant amplification of an electromagnetic field at the localized plasmon resonance. The condition of the optical resonance obtained in the work is applicable to layered spheres with an arbitrary number of layers of any size and material.

An experimental study of absorption, distribution, metabolism, and excretion from the body of radioisotope-labeled nanoparticles (NPs) of elemental Se in comparison with the traditional form of this trace element (sodium selenite) has been performed, being administered in the gastrointestinal tract of rats that were normally supplied with Se or experiencing its nutritional deficiency. Nuclear activation analysis is used for the detection of Se in the biological tissue, which is based on the measurement of a gamma-emitting label [⁷⁵Se₃₄] that is introduced in the Se NPs or its salt by thermal neutron irradiation in a nuclear reactor. It is shown that Se NPs administered into the gastrointestinal tract have bioavailability comparable to the salt form of this element. According to some experimental data, the metabolic assimilation of both forms of Se is greater in animals that suffer from a deficiency in this element when compared to those that are normally supplied with it. There are some differences in the kinetics of accumulation of Se NPs and its salts in the blood and liver, which can be explained by the presence of limiting steps in the absorption and biotransformation of Se-containing NPs. The retention of Se that is administered in the form of NPs or salts to Se-deficient animals differs significantly. These results demonstrate the capacity of the Se NPs to be a source of Se in a new generation of biologically active food supplements.