Vol 14, No 9-10 (2019)

The carbon nanotube efficiency index in a nanocomposite is introduced as the ratio of the load carried by carbon nanotubes (CNTs) at a given average deformation of a matrix to the maximum possible load that can be transferred to the nanotubes at this deformation. The best published results on polymer strengthening with an assessment of CNT efficiency are reviewed. Analysis of the data in publications shows that the upper boundary of CNT efficiency is reached in polymers if a network of interconnected nanotubes is formed inside the polymer. Such a network can be formed by integrating nanotubes into a polymer matrix through covalent binding of nanotubes or by physical entanglement of nanotubes with each other. In thermoplastic crystallizing polymers, the upper boundary of CNT efficiency can also be reached by increasing the degree of polymer crystallinity due to participation of carbon nanotubes and improvement of the microstructure of the polymer including the orientational elongation of the nanocomposite. Nanocomposites of polymers with CNTs are promising for practical application if the nanotube efficiency is close to or exceeds the upper limit.

The preparation of hydro- and aerogels based on reduced graphite oxide and gold nanoparticles obtained by the method of Turkevich is described. According to the transmission electron microscopy data, gold nanoparticles have a spherical shape and an average size of 16‒18 nm. Sorption of methylene blue dye from water solutions was used to characterize the obtained 3D structures. The sorption properties of hydro- and aerogels were compared; it was shown that aerogels sorb the dye more efficiently (>80%) than a composite based on hydrogel (~50%). The formed porous 3D structure of the aerogel efficiently sorbs the molecules of the dye, while the gold nanoparticles facilitate its destruction under the visible light. Sorption by aerogels of pure graphite oxide is most efficient at room temperature, in a neutral medium, and in the absence of additional reducing agents. Introduction of gold nanoparticles to aerogels led to an increase of the maximal sorption by 15%.

Innovation concerned with hybridization of nanosiezed chitosan with nanoparticles of a disperse dye under the onset of sonication was studied. Three techniques were outlined describing the nanoparticles preparations of chitosan, disperse dye and chitosan /disperse dye nanoparticles. Thus obtained hybrid nano colorant auxiliary was found to possess different hydrophobic/hydrophilic characteristics as well as variable color intensity depending upon the ratio of the disperse dye in the chitosan/dye mix. When applied to textile fabrics (flax, polyester, and polyester/flax blend) as per the pigment printing technique, the nano colorant hybrid display multifunction antibacterial activity and coloration ability. The prepared nanoparticles of chitosan/ disperse dye were characterized using TEM and XRD. The coloured hybrid was applied in textile printing using silk screen technique. The printed samples were evaluated by measuring colour strength, fastness properties, means of print fixation and antibacterial activity.

We used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to study changes in the composition of the plasma membranes of human fetal fibroblasts under the action of nanosized anions of silicon molybdic acid. The dependences of the mass spectra of the main lipids of the plasma membranes on the silicon molybdate concentration were measured and interpreted; the dependences correlate with the layer-by-layer distributions and with the affinity of cholesterol for phospholipids. A new effect for cell biochemistry was discovered, that is, a significant decrease in the relative concentrations of cholesterol and sphingomyelin in plasma membranes under the effect of multiply charged heteropoly anions (HPAs). In aqueous silicon molybdate solutions with a concentration of c ≈ 10 µM/L and an exposure time of 48 h, the amount of cholesterol in plasma membranes decreased by 2–2.5 times, while the amount of sphingomyelin decreased by 20–25%. A new mechanism is proposed for the initial effect of HPA on plasma membranes, which consists of selective etching by multiply charged anions. According to the proposed mechanism, cholesterol and sphingomyelin, the main regulators of permeability and microviscosity of plasma membranes, are extracted from the plasma membrane at the first stage of the interaction of the polyoxometallate anion with the cell. As a consequence of the increased permeability of the plasma membranes in cells, acceleration of vital transmembrane and lateral processes may occur.

Under a single 4 hour inhalation exposure to aerosol containing an aqueous suspension of calcium oxide nanoparticles (CaO) in an actual concentration of 6.68 mg/m³, the accumulation of calcium increased in the lungs (by 1.52 times), in the brain (by 1.55 times) and in the liver (by 1.25 times) relative to the control, while exposure to a microdispersed analog in a concentration of 6.37 mg/m³ resulted in an increase in the indicator only in the brain (by 1.27 times). At the same time, the calcium concentration in the brain of animals in the experimental group is higher than in the comparison group (by 1.22 times). After exposure to CaO nano- and microparticles a subarachnoid hemorrhage in the brain tissues was found. The development of pathomorphological changes in the form of lymphoid tissue hyperplasia, eosinophilia, acute arterial plethora, and hemorrhagic lung infarcts, as well as the hydropic and hyaline-drop dystrophy of parenchymal liver tissue was observed only after exposure to CaO nanoparticles. The identified features of the bioaccumulation and pathomorphological changes under inhalation exposure to CaO nanoparticles demonstrate that the studied nanomaterial has a higher level of toxicity in comparison to its microdispersed analog.