Vol 11, No 3-4 (2016)

The qualitative and quantitative composition of hybrid Si/SiO_x/SiO₂/OH(D) nanoparticles synthesized from silicon monoxide has been determined by X-ray photoelectron spectroscopy. The nanoparticles are composed of a Si crystalline core and a SiO_x/SiO₂/OH(D) shell, where SiO_x is the interface of intermediate oxides corresponding to the Si¹⁺, Si²⁺, and Si³⁺ valence states of silicon and SiO₂/OH(D) is the external shell of the nanoparticle. The chemical composition and average stoichiometry of deuterated and nondeuterated nanoparticles have been determined; the identified compositions have been compared. The dependence of photoluminescent properties on the composition of the samples has been discussed. Two forms of hydrophilic silicon nanoparticles with identical crystalline cores—photoluminescent deuteriumpassivated particles oxidized in completely deuterated dimethylsulfoxide and nonphotoluminescent hydrogen- passivated reference samples oxidized in dimethylsulfoxide—have been studied by broadband femtosecond spectroscopy. It has been found that there are significant differences in the ultrafast spectral–temporal induced absorption dynamics of these two forms in the energy range corresponding to the calculated bandgap of the nanoparticles. The observed difference has been attributed to the specific features of the relaxation of excited charge carriers in the energy states responsible for photoluminescence in the red spectral region.

In this work we present the results of the synthesis of magnetite–gold nanoparticles with a core–shell structure. The preparation is carried out in several stages: synthesis of the core, coating with a gold shell, purification of magnetite–gold particles from an uncoated magnetite, and functionalization of the surface with sulfur-containing ligands. The conditions needed for the functionalization of nanoparticles with lipoic acid and mercapto-methoxy polyethylene glycol are indicated in detail, making it possible to determine the optimal conditions needed to achieve an efficient purification and a maximum concentration of the particles in a solution required for biological tests. The possibility of remotely controlling the chymotrypsin properties using an alternating magnetic field has been demonstrated by the example of magnetite–gold nanoparticles. The magnetite–gold nanoparticles which we have obtained are promising for future biomedical applications.

Organomodified layered aluminosilicates and hybrid organic–inorganic nanocomposites based on Na⁺-montmorillonite, Cloisite 20A, and allene hydrocarbons have been obtained under the action of rhodium chloride. The intercalation polymerization includes the cation-exchange reaction, the intercalation of hydrated rhodium chloride (RhCl₃ ∙ 4H₂O) into layered silicates, and the in situ oligomerization of allene or 1,1-dimethylallene. The reaction is performed in polar (Na⁺-montmorillonite) and nonpolar (Cloisite 20A) solvents. Detailed X-ray diffraction studies of the resulting products show that, depending on the reagent concentrations and ratios, oligoallene- and oligo(1,1-dimethylallene)-modified nanofillers with both intercalated and exfoliated morphologies can be obtained. Three independent phases are detected, which suggests the formations of structures with different types of organophilic layers. The structures and properties of polymers and composites obtained by the rhodium chloride-catalyzed polymerization of allene in toluene or a water-ethanol mixture in the presence of aluminosilicates are studied by X-ray diffraction, IR spectroscopy, and differential scanning calorimetry. The polyallenes synthesized in different media are shown to have identical structures (1,2,1,2-addition) and crystallinities (m.p. 124–126°C), but different degrees of aluminosilicate exfoliation in nanocomposites.

It has been shown that the high-temperature hydrogen treatment of aluminum oxide nanowires coated with a monolayer of titanium oxide causes them to curl into nanotubes as a result of self-organization. The physicochemical properties of the nanotubes of a composite aluminum oxide aerogel coated with titanium oxide have been studied using X-ray phase analysis (XRD) and transmission electron microscopy (TEM). As a result of TiO₂/Al₂O₃ nanofibrous aerogel treatment with hydrogen, a conversion of amorphous aluminum oxide fibers into tubes of nanocrystalline η-Al₂O₃ occurs, but in this case the titanium dioxide monolayer does not form a separate phase. A study of the porous structure by the low-temperature adsorption of nitrogen vapors has shown that the aerogels of TiO₂/Al₂O₃ nanotubes have a developed mesoporous structure with a small amount of micropores and a specific surface of more than 300 m²/g. An increase in the temperature of hydrogen treatment first leads to the growth of an increase in the specific surface to 348 m²/g at 923 K, and then to a gradual decrease to 145 m²/g at 1123 K. In this case, the diameter of mesopores corresponding to a maximum on a curve of the pore size distribution decreases from 35 nm for a freshly prepared sample to 25 nm at 923 K and to 20 nm at 1123 K. The most homogeneous pores of a 25 nm diameter have the samples activated at 923 K. As a result of the high-temperature hydrogen treatment of the samples, the number of primary adsorption centers of water vapor adsorption decreases about two times. The resulting samples of TiO₂/Al₂O₃ aerogels are close in structure to the initial aluminum oxide, whose wires just form nanotubes having a surface coated with titanium dioxide. As a result of the interaction between molecules of titanium dioxide adsorbed on the surface of aluminum oxide tubes, a substantial densification of the composite structure occurs.

In this paper the results of validation of originally developed device-modeling tool on realistic organic-based devices are presented. Hole-only devices with α-NPD as a hole conductive layer are modeled. All material properties of α-NPD are obtained from first-principles calculations at atomistic level, and charge carrier mobilities are calculated using the Monte-Carlo method. A comparison of the simulation results with experimental data obtained for real devices shows a good correspondence. We also performed the sensitivity analysis of calculated results to model parameters. It is shown that the uncertainty in the dispersion of site energies σ makes the largest contribution to the uncertainty of predicted current-voltage characteristic of an organic electronic device.

Thermally assisted magnetic random access memory (TAS-MRAM) nanodevices are promising candidates for future memory applications, because they provide non-volatile data storage at fast operation and low energy consumption. In this work, we analyze operating regimes of these devices using macrospin and micromagnetic modeling. It is shown that, for the successful performance of write and read operations in a TAS-MRAM device, the intrinsic magnetic anisotropy of ferromagnetic layers must not exceed some critical value. The relationship between the device parameters and the value of critical magnetic anisotropy is explained using analytical model and proved by the results of numerical simulation. This analysis is important for the future downscaling of TAS-MRAM nanodevices.

The ultrafast relaxations of electronically excited states of styryl dyes, viz., 4-[(E)-2-(3,4-dimethoxyphenyl)- 1-ethylpyridinium] perchlorate (1) and 1-(3-ammoniumpropyl)-4-[(E)-2-(3,4-dimethoxyphenyl) vinyl]pyridinium diperchlorate (2), and their inclusion complexes with cucurbit[7]uril (СВ[7]) have been studied in aqueous solutions as a function of the fluorescence wavelength by femtosecond laser-induced fluorescence spectroscopy.For all dyes and their complexes, the fluorescence decay curves are fitted satisfactorily by the sum of two and three exponentials. The relaxation of electronically excited states in the blue wing of fluorescence band contains a component with a short decay time of about 100–200 fs and the red wing displays a rising component with a characteristic time of the same order of magnitude. In addition, the fluorescence decay includes a component with a characteristic time of about 2 ps, which is independent of complexation and fluorescence wavelength. The addition of СВ[7] to aqueous solutions of dyes 1 and 2 results in an increase in the longer relaxation times from ≈50 ps for the free dyes to 100–150 ps for the bound ones. The extra positive charge of dication 2 has almost no effect on the photophysical properties compared to cation 1, which agrees with quantum chemical calculations of the structures of inclusion complexes. A considerable increase in the fluorescence lifetime can be attributed to the increase in the potential energy barrier between the excited state of dye and the conical region on the potential energy curve, which is assumed to be caused by the displacement of the dye cation from the equilibrium state deep into the cavity within the first several picoseconds after laser pulse excitation.

The purpose of this work is to study cytokine synthesis in the brain, blood, spleen, and liver and cfos expression in a rat brain 24 h after the intranasal administration of single-walled carbon nanotubes (SWCNTs) at a low dose (1 μg per rat, or 4 μg/kg). A RT-PCR analysis of cytokine mRNA synthesis has demonstrated that the cytokine profile in the brain does not change significantly under the influence of SWCNTs, but a reduction of the total content of all cytokine mRNA is observed. At the same time, the mRNA content of colony-stimulating factor IL-5 and proinflammatory cytokine IL-18 increases in the liver; only IL-18 mRNA increases in the blood, which indicates a possible activation of Th-2 lymphocytes and macrophages in the liver and only macrophages in the blood. In the spleen, mRNA levels of all cytokines that were detected in the norm were decreased. This indicates a suppression of the transcription of cytokines in the spleen, the main organ of immune system, and hence an immunosuppressive effect of SWCNTs. Administration of SWCNTs does not alter c-fos expression in 35 of 43 brain structures studied compared to the control. The c-fos expression increased only in the olfactory bulb and in the piriform cortex and in six brain structures this index was reduced; i.e., SWCNTs have little effect on the activity of brain structures. It is assumed that the low-dose intranasal administration of SWCNTs can be used in medicine for drug delivery to the brain. In addition, it is not excluded that the immunosuppressive properties of SWCNTs can be applied for the prevention of transplant rejection and treatment of autoimmune disorders. When using SWCNTs for medical and biological purposes it is necessary to take into account the probability of their immunosuppressive effects.

The cytogenetic and cytotoxic activities of nanosilver particles and silver sulfate in germ cells in vivo were studied in a model similar to the potential impact on humans for the first time. We investigated nanosilver particles with a diameter of 14 nm coated with gum. The substances were ingested by male CBAB6F1 mice for 14 days with drinking water over a wide range of concentrations: 0.1, 50, and 500 mg/L (0.01, 5, and 50 mg/kg). Silver nanoparticles caused a slight statistically significant increase in the frequency of micronucleated spermatids to 0.57‰. Genomic instability affects the cell kinetics: it resulted in an increase in apoptosis from 3.4% (control) to 6.4% (50 mg/L), and it reduced the level of multinucleated spermatids from 15.6% (control) to 11.1% (50 mg/L). This phenomenon can be seen as a compensatory response aimed at death of genetically damaged cells and the expedited renewal of round spermatids by the disintegration of multinucleated spermatids. The minimally tested concentration of silver sulfate increased apoptotic activity. No other changes in the same mode of action of silver sulfate were observed, indicating a more pronounced effect of silver nanoparticles when compared to its ionic form in the germ cells of mice.