Vol 13, No 11-12 (2018)

In this paper, the synthesis of nickel nanopowders by the chemicometallurgical method under dynamic conditions, when the composition of the gas medium is changed in the process of synthesis (argon is changed for hydrogen or otherwise) with the retention of the overall time of synthesis, is studied for the first time. It is demonstrated that the synthesis under dynamic conditions is an efficient method for controlling the morphology and sizes of synthesized nanopowders.

The structure of nanocomposites based on opal matrices in relation to the type of filling the structural voids by amorphous and crystalline substances is investigated using small-angle X-ray and neutron scattering (SAXS and SANS, respectively). An analysis of neutron-scattering data shows that the samples are ordered structures with parameters corresponding to the face-centered cubic lattice. The order of filling the octahedral and tetrahedral voids of the opal matrix with different substances affects the SANS reflection patterns. It is shown that the scattering curves can be described and interpreted, depending on the composition and filling sequence of the ordered nanocomposite, using different models, e.g., from the standpoint of models of monodisperse systems accounting for the interparticle interference or polydisperse systems of scattering irregularities. The structural parameters of ordered nanocomposites based on opal matrices of different compositions are determined.

Per the literature, the thermodynamic stability criterion of the dispersed system of nanosized phases in metal melts is reproduced, with the latter considered the specific change in free energy (referred to the unit of change in the contact surface of the phases) of the disperse system aggregation. For iron–carbon melts with [C] > 2 wt %, according to the published scientific results, the selection of two refractory phases SiC and TiC_0.8N_0.16O_0.04 for introduction into the Fe–C–Si–Mn–P–S–O melt is justified. The preparation of nanophases, the preparation of briquettes of a composite material, and the method used to study the interfacial interaction of nanophases with sulfur and oxygen of the melt is described. It is shown that a decrease in the surfactant content of the nanophase content upon 5–10 min of exposure indicates the interaction of the surfactant with nanoparticles, and the concentration dependences are characterized by extreme minimum values.

This paper reports on the creation of a new composite sensor material for detecting molecular oxygen, in which the fluorescent indicator, Pt (II) 5,10,15,20-tetrakis(2,3,4,5,6-pentafluorophenyl)-porphyrin, is adsorbed on mesoporous silica particles distributed in a fluorinated polymer performing the functions of the gas transmission line and protection against leaching. A set of methods is used to determine the optimal conditions for the monolayer adsorption of the dye. It is found that unwanted multilayer adsorption with the formation of dimers begins when the ratio of the diameter of the average adsorption center to the average diameter of the indicator molecule is less than three. An original method is applied for the encapsulation of microparticles with the formation of a surface salt of fluorinated surfactants, which protect the material at the manufacturing stage before its deposition to the substrate. It is shown that the material has a linear calibration dependence in a range from 0 to 40°C, a response time in the gas phase of less than 10 s, and photostability sufficient to function as an oxygen sensor for at least a year.

Gold nanoparticles (GNPs) and their conjugates are widely used as labels in bioanalytical methods. One of the main characteristics that determine their unique plasmon properties is their size. In this work, the growth of bare and protein-modified (with streptavidin) GNPs in the presence of hydrogen tetrachloroaurate and hydroxylamine was studied. Three initial preparations of GNPs with average diameters of 30.5 ± 7.7, 19.2 ± 1.6, and 4.4 ± 0.6 nm were obtained. An increase in size of GNPs at different initial particle sizes, reagent concentrations, presence/absence of protein coating was characterized using the methods of optical spectrophotometry, dynamic laser light scattering and transmission electron microscopy. The presence of sorbed proteins was shown to reduce the growth rate and affect the morphology of the forming nanoparticles. The conditions (1–10 mM hydroxylamine, 30 mM hydrogen tetrachloroaurate) that ensure the maximum increase in the size of GNPs (up to ≈70 nm) and their conjugates in homogeneous systems without the formation of unstable aggregates were determined.