Vol 13, No 3-4 (2018)

It is shown that bis-quaternary salts of 4,4′-dipyridyl (viologens) stimulate the J-aggregation of anionic cyanine dyes in an aqueous solution. It is concluded that the behavior of multiply charged inorganic and organic cations is similar: both types of polycations result in the self-assembly of ordered J-aggregate structures from dimers. It is found that multichromic J-aggregates with the participation of cationic cyanine dyes are formed on the “platform” of J-aggregates built of anionic cyanine dyes and dications of viologens. Thus, we discuss the self-assembly of highly organized structures in which, along with photosensitive exciton semiconductors from organic dyes, π-conjugated organic molecules are included that can participate in secondary dark processes of separation of charges of Frenkel excitons.

In this study, pure and Sm³⁺ doped Fe₃O₄ nanoparticles were prepared via a microwave assisted synthesis in water solution. The samples were characterized by TEM, XRD, XANES, and VSM techniques. The structure and morphology, Fe and Sm oxidation states, the oxidation resistance and magnetic properties of pure and Sm doped Fe₃O₄ nanoparticles were studied. TEM and XRD results show that Sm doped Fe₃O₄ nanoparticles have a good dispersion and are smaller than pure Fe₃O₄ nanoparticles. The Fe and Sm oxidation states of pure and Sm doped Fe₃O₄ nanoparticles were studied by means of XANES analysis. The magnetic properties of Sm doped Fe₃O₄ nanoparticles determined by VSM exhibit superparamagnetic behavior with high saturation magnetization. It was found that Sm doping in a small amount makes it possible not only to reduce the sizes of magnetite nanoparticles but also to improve their oxidation resistance and increase their saturation magnetization value. These pure and Sm doped Fe₃O₄ magnetic nanoparticles are expected to be used in a number of biomedical applications.

The effect of the filler content on the optical absorption spectra, electroconductivity, and surface morphology of thin nanoocomposite films based on poly(n-xylylene)–tin (PPX–Sn) has been studied. The films under study are prepared in vacuum by cryochemical synthesis on polished quartz, glass-ceramics, and silicon substrates. After completing the preparation, the samples are exposed to air for some time prior to measurements. With an increase in the filler content, a nonmonotonic change in both surface morphology of films (by atomic force microscopy) and adsorption spectra is found. An analysis of the spectra shows that, at the filler concentration C ≤ 9 vol %, tin in the composite is in the oxidized form of SnO₂, while at C = 12 vol % it is in a metal state, respectively. With an increase in C from 4 to 12 vol %, the increase in conductivity of nanocomposites is more than 7 decimal orders, with a sharp change in the region of C ≈ 9–12 vol %. The conductivity of the film consisting of nanoparticles (C = 100 vol %) is found to be low and comparable with that for composites with C = 4–5 vol %. With a decrease in the temperature from 300 to 15 K, the resistance of the sample with C = 12 vol % is found to decrease, while that for all other samples increases by the activation law. The activation energy with an increase in the filler concentration to 9 vol % is found to decrease, while that for the sample with C = 100 vol % increases by almost an order of magnitude. The most significant changes in the properties and morphology of the surface of nanocomposites are observed at a concentration of ~9 vol %, which apparently is the percolation threshold.

A simple technology is proposed for preparing a graphene/silicon photodiode with a Schottky barrier. CVD graphene is transferred to a polymer substrate via lamination. The polymer film with graphene is then glued to the surface of a silicon plate via thermal compression. The contacts are deposited on graphene and silicon with a silver paste. The photodiode obtained in this way has the following characteristics: sensitivity of 0.37 A/W, external quantum efficiency of 0.88, and normalized equivalent noise power of 1 pW/Hz^1/2. These data are obtained for a wavelength of 520 nm. The range of electromagnetic radiation detected with the photodetector is 320–1100 nm.

The role of the environment on the dynamics of the photoburning processes of the red–infrared photoluminescence (PL) of hybrid silicon nanoparticles (npSi/SiO_x) under the influence of continuous laser radiation (410 and 635 nm) in different media (in a helium or oxygen atmosphere at low pressures, in carbon tetrachloride solutions, in polymer matrices, and in vacuum) is studied. It is established that the presence of electron-acceptor molecules or compounds in the components of the medium increases the rate of luminescence photoburning (photosensitivity) of npSi/SiO_x. The lowest photosensitivity is observed when the nanoparticles are in vacuum or in a helium atmosphere. It is shown that the photoburning rate depends on the wavelength of the exciting radiation. A mechanism of photosensitivity of npSi/SiO_x is proposed which is based on recharging the centers involved in the photoluminescence process and located in the oxide shell or at the core–shell interface.

This work is dedicated to the synthesis of a GO@Fe₃O₄@DOX multifunctional nanocomposite composed of graphite oxide, superparamagnetic iron oxide nanoparticles, and the drug doxorubicin. The final product combines double magnetic and molecular targeting to tumor tissues. Superparamagnetic Fe₃O₄ nanoparticles are first chemically deposited onto a surface of graphite oxide (GO) with the acquisition of a double GO@Fe₃O₄ composite. The material is then bound with the antitumor drug doxorubicin. The morphology, phase composition, and magnetic and optical properties of synthesized samples are characterized via thermal gravimetry, X-ray diffraction, magnetic susceptibility measurements, transmission electron microscopy, and via UV-visible and Raman spectroscopy. The optimal ratio of graphite oxide, iron oxide, and doxorubicin for the creation of a potential precursor of the new drug is established. The presence of doxorubicin and iron oxide in the composite is confirmed, making it possible to use an external magnetic field for targeted drug delivery towards the affected tissues. It is also shown that the composite retains its stability for a month in solutions with physiological pH values.

The relationship between synthesis conditions, structure, and properties of the baddeleyite-based engineering nanostructured composite zirconia ceramic (natural zirconia mineral) with modifying alloying elements is studied. The elaborated composites possess high physical and mechanical properties at a level that is not only not inferior, but even superior to those of analogous ceramics prepared from precipitated zirconia (e.g., density is 0.95 of the theoretical value, the hardness reaches 12 GPa, the Young modulus is 220 ± 15 GPa, and the fracture toughness reaches 9 MPa m^0.5). The embedding of carbon nanotubes (CNTs) is shown to alter the physical and mechanical properties of ceramics: the hardness is somewhat reduced, but fracture toughness K_C gains more than 10%.

Cryochemical approaches have been used to synthesize hybrid systems consisting of a cryomodified β form of dioxydine (particle size of 30‒350 nm) and silver or copper nanoparticles (average size of 5‒18 nm). These hybrid composites and their precursors are incorporated into biopolymer cryostructures based on gelatin and calcium alginate. Hybrid composites based on metals and antibacterial drugs are very active in the inhibition of growth of E. coli 52, S. aureus 144, and M. cyaneum 98 in comparison with their separate components.

Metal and metal oxide nanoparticles are considered a basis for the development of antibacterial agents of new generation. Dental drugs are among the promising fields of their application. Experimental samples are obtained and microbiological studies are carried out with the dental plaque microflora and aqueous solutions of Fe₃O₄, SnO, ZnO, Ag, and Cu nanoparticles 10–100 nm in size and with a mass concentration of 1.53–10.12 mg/L. The study of the effect of colloid solutions on the culture of dental plaque microflora shows that the antibacterial properties predominantly depend on the chemical composition of the particles of the dispersed phase. Dispersed systems containing magnetite with an initial concentration of 2.11 mg/L, as well as silver (2.39 mg/L), copper (2.07 mg/L), and zinc oxide (7.03 mg/L), prove to be the most efficient ones. The results of this study may be used to develop promising mouth rinse and other antibacterial drugs based on aqueous solutions of metal and metal oxide nanoparticles.

The effect of concentrations in the media of nanoparticles of silica, magnetite, and carbon nanotubes, as well as magnetic metallopolymer nanocomposites based on unsaturated dicarboxylates of cobalt (II), nickel (II), and iron (iron itaconate and citraconate and maleates of nickel, cobalt, and iron), on the growth of the soil-forming micromycete Trichoderma asperellum is studied in this work. As a result, the toxicity of a nanocomposite prepared by the thermal decomposition of cobalt maleate is revealed at a concentration of 10^–4 parts by weight in the culture media. For the rest of the nanoparticles studied, neither acute toxicity nor the significant inhibition of the micromycete growth are found. For all types of particles studied, it is revealed that the particle concentrations in the media of (1–5) × 10^–6 parts by weight nonspecifically stimulate the regrowth of fungi.