


Vol 11, No 5-6 (2016)
- Year: 2016
- Articles: 17
- URL: https://journal-vniispk.ru/2635-1676/issue/view/13602
Article
Multilayer J-aggregates of cyanine dyes
Abstract
It is shown that the introduction into the aqueous solution of anionic thiamonomethinecyanine of the Mg2+ cation promotes the formation of the multilayer dye J-aggregates. It is also established that, on the J-aggregates or on the metallocomplex J-aggregates of anionic thiamonomethinecyanine, a multilayer and simultaneously multichrome system of new J-aggregate is formed due to the additional introduction of cationic cyanine dye into the solution, which absorbs light in a different region of the spectrum than anionic dye.



Multichromic J-aggregates of cyanine dyes for visible and IR range of spectrum
Abstract
It is shown that on the platform of the metallocomplexis J-aggregates of anionic cyanine dyes, the “self-assembly” of J-aggregates of different cationic cyanine dyes occurs according to the matrix-synthesis method. It is concluded that the matrix synthesis of multichromic J-aggregates is promising technology for the self-assembly of wide-zone nanooptical elements for the visible and IR ranges of spectrum.



Microstructure and surface morphology of thin AlN films formed on sapphire by dual magnetron sputtering
Abstract
Results of studies of the effect of the discharge current on the crystalline structure, surface morphology, and thickness of thin AlN coatings deposited by reactive dual magnetron sputtering on c-axis oriented sapphire wafers have been described. Using grazing incidence X-ray diffraction, it has been determined that the coatings have a wurtzite crystalline structure and at least two types of grains with different orientations of the (002) planes. Electron microscopy has revealed that the coatings are composed of vertically aligned columnar grains and a nucleation layer. The grains are uniformly distributed over the substrate surface; each of the grains consists of smaller crystallites. It has been found that the discharge current largely affects the concentration of grains of different orientations and has hardly any effect on the size of the nuclei.



Effect of CO atmosphere on morphology and electrochemically active surface area in the synthesis of Pt/C and PtAg/C electrocatalysts
Abstract
An effect of CO atmosphere on the microstructure of Pt/C, PtAg/C, and Ag@Pt/C electrocatalysts formed in the synthesis and on the electrochemically active surface area (ECAS) has been studied. Synthesis is carried out via the joint or sequential chemical reduction of silver and platinum precursors in a suspension of Vulcan XC-72 disperse carbon carrier. Adsorption of CO molecules on a surface of platinum and Pt-Ag is shown to hamper their growth and aggregation, leading to a considerable increase in ECAS of platinum, as well as Pt/C and PtAg/C materials to be synthesized. The impact of CO on the morphological characteristics of the Ag@Pt/C materials containing a significant proportion of bimetallic nanoparticles (NPs) with an Ag-core/Pt-shell structure is less because of the weak adsorption of CO on the silver surface. ECAS values of platinum in the materials synthesized in the CO atmosphere were 152, 88, and 75 m2/g for Pt/C, PtAg/C, and Ag@Pt/C materials, respectively.



Influence of mechanical activation mode on morphology and phase composition of Al-2Mg-nC nanostructured composite material
Abstract
This article discusses peculiar features of formation of the structure and phase composition of powdered nanostructured aluminum matrix composite materials reinforced by graphene-like structures obtained by combined mechanical activation. The morphology of the powders has been studied and a neural network model has been developed which describes the dynamics of crystallite disintegration upon mechanical activation as a function of processing time and concentration of carbon nanostructures.



Study of melting processes in semicrystalline polymers using a combination of ultrafast chip calorimetry and nanofocus synchrotron X-ray diffraction
Abstract
This work is devoted to the development and application of a new experimental method that combines in situ ultrafast calorimetry on a chip with nanofocus synchrotron X-ray diffraction. In the present work, this method is used to study the melting mechanisms of samples of semicrystalline polymers with the mass of a few tens of nanograms. Such studies are relevant when working with materials that are characterized by complex phase behavior, for example, prone to transitions into metastable states or demonstrating fast processes of structural adjustment during thermal treatment.



Synthesis of tungsten sulfide nanoparticles and their tribological properties as additives for lubricating oils
Abstract
Tetrathiotungstates with different alkyl groups have been synthesized by an exchange reaction between ammonium tetrathiotungstate and tetraalkylammonium halides. Synthesized samples are analyzed by elemental analysis and optical and thermal methods. Nano-WS3 particles that are stable and soluble in nonpolar hydrocarbons are prepared by thermolysis of alkyltetrathiotungstates. The average particle size of nano-WS3 is about 10–100 nm and depends on the nature of raw tetraalkylammonium halides. It is shown that nanoparticles of WS3 are soluble in Vaseline oil (1–2 wt %) and exhibit antiwear activity.



The influence of size of modifying nucleation centers of tungsten and antimony compounds on the structure and magnetic properties of CrO2 nanoparticles
Abstract
This article deals with the investigation of magnetic chromium dioxide-based nanopowders obtained under hydrothermal conditions in the presence of Cr2WO6 and CrSbO4 modifying additives. The critical nucleus diameter of the synthesized homogeneous chromium dioxide nanoparticles has been found to be around 13 nm.



Luminescence in GeOx films containing germanium nanoclusters
Abstract
Metastable GeOx films have been deposited onto a Si substrate by the electron beam evaporation of GeO2 powder in high vacuum. The optical properties of Ge nanoclusters in GeOx films after a series of annealing are studied by Raman spectroscopy, ellipsometry, cathodoluminescence, and photoluminescence. After the annealings, the cathodoluminescence peaks are first found in GeOx films in the visible spectral range (400 and 660 nm) at room temperature. The cathodoluminescence may be associated both with the existence of nonground (excited) levels in Ge nanoclusters and allowed optical transitions from an excited to ground level and surface states at Ge/GeO2-matrix interface or defects inside a Ge nanocluster. The photoluminescence signals in a yellow-green region (2.1–2.4 eV), which are observed for GeOx films after annealings, can be explained by quasi-direct optical transitions in Ge nanoclusters.



Molecular diodes and negative differential resistances based on polyoxometalates
Abstract
By measuring the tunnel conductivity of polyoxometalates (POM) and their organic derivatives in experiments with a scanning tunnel microscope (STM), effects have been found which are promising for use in nanoelectronics. Large-scale multiple negative differential resistances (with record peak-to-valley ratios up to 102) have been observed under conditions which do not require low temperatures and high vacuum. The diode properties of organo-polyoxometalate complexes with coefficients of rectification up to 35–40 are revealed. A mechanism of biresonance tunnel electron transport in strong electric fields, which explains the effects, has been developed. A strategy for selecting nanomaterials which can improve the functional properties of molecular electronic elements based on the optimization of the composition and architecture of polyoxometalate complexes has been proposed.



Synthesis of highly photostable NIR-emitting quantum dots CdTeSe/CdS/CdZnS/ZnS
Abstract
The use of near IR (NIR) fluorescent labels is promising in such areas as molecular biology, diagnostics and imaging, because this spectrum region is absorbed minimally by tissues and is significantly shifted from the autofluorescence spectra of biological materials. The development of NIR LED sources is of interest as well. One of the key limitations of most NIR fluorophores is lack of stability to environmental conditions, in particular their low photostability. In this paper we propose a method of synthesis of luminescent core/shell cadmium telluride-selenide nanoparticles with quantum yield of 80% and increased resistance to photodegradation.



Synthesis and optical properties of nanostructured ZnS:Mn films
Abstract
The experimental results on the synthesis of ZnS:Мn nanoparticles, as well as the study of their structure and optical and photoluminescence characteristics, are reported. The ZnS:Мn nanoparticles and thin films on silicon and glass substrates are grown via hydrochemical deposition from the solution containing thiourea, zinc chloride, manganese chloride, and dimethyl sulfoxide. The internal structure of the samples is probed via X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The spectral dependence has allowed a determination of the bandgap width in ZnS:Мn nanoparticles. It is found the photoluminescence peak intensity increases with the enlargement of nanoparticles.



Propagation of electromagnetic wave in pendry lens
Abstract
This work investigates the propagation of a monochromatic electromagnetic wave in a periodic layered medium with stepped refractive index. The solution of Maxwell’s equations for piecewise homogeneous medium is proposed by means of which the wave equation in closed form is analytically solved. On the basis of the solution, the propagation of electromagnetic wave in a superlens (Pendry superlens) generated by a metal plate of nanosized thickness has been studied. The computations have proven that, using the superlens, it is possible to achieve angular resolution exceeding the diffraction limit. In addition, it has been demonstrated that negative refraction occurs in such lens.



Study of titanium dioxide photocatalytic properties by decomposition of methylene blue (C16H18N3SCl) aqueous solution
Abstract
The photocatalytic properties of titanium dioxide obtained by plasmodynamic synthesis technology have been studied in this work. The study is carried out by measuring changes in the optical density of a methylene blue solution whose decomposition took place under the action of a nanodisperse titanium dioxide in sunlight. The result we have obtained is that the addition of titanium nitride in dioxide shifts the photocatalysis zone to a visible spectral range without any requirement for nitriding the very titanium dioxide with the formation of complex oxynitrides. This makes it possible to considerably simplify the technology in the future. However, a substantial increase in synthesized titanium nitride quality is needed for the photocatalysis process to proceed gradually.



Visualization of the spatial distribution of Ag ions in cyanobacteria Anabaena sp. PCC 7120 by time-of-flight secondary ion mass spectrometry and two-photon luminescence microscopy
Abstract
Cyanobacteria Anabaena sp. PCC 7120 have been analyzed by time-of-flight secondary ion mass spectrometry and two-photon luminescence microscopy. The reduction of Ag+ ions to silver nanoparticles inside the cells is detected. The silver ion signal is shown to be much greater inside certain cells. Comparing the distribution of Ag ions with optical images allows us to identify these cells as heterocysts, which are specialized nitrogen-fixing cells.



Effect of DNA methylation on the interaction with tetrahydrocortisol–apolipoprotein A-I complex
Abstract
The effect of GCNGC site methylation on the DNA binding to tetrahydrocortisol–apolipoprotein A-I complex was shown by atomic force microscopy and enzymatic analysis. Methylation of GCNGC sites alters the mechanism of interaction of tetrahydrocortisol–apolipoprotein A-I complex with DNA and leads to the aggregation of the DNA-protein complexes. It was assumed that the involvement of complexes of steroid hormones with apolipoprotein A-I in the process of chromatin restructuring is associated with the processes of DNA methylation/demethylation.



Optimization of composition of ormustine liposomal dosage form
Abstract
The improvement of the composition and technology for the preparation of the liposomal dosage form of ormustine is under consideration. Liposomes are prepared from egg lecithin, cholesterol, and PEG-2000-DSPE by the film hydration method, with 0.1% citric acid being added to the composition to stabilize the liposome dispersion. The efficiency of loading with ormustine is (60 ± 5)% and the average vesicle size is (190 ± 20) nm.


