Том 14, № 1-2 (2019)

The effect of the nature of a filler and its concentration (C ~ 0–100 vol %) on the IR spectra (500–4000 cm^–1) of thin nanocomposite films based on poly(p-xylylene) and sulfides (PPX–PbS, PPX–CdS, and PPX–S) was studied. Films with a thickness d ~ 0.5 μm are produced via low-temperature vapor deposition polymerization on silicon substrates. The common and specific variations in the IR-spectra of nanocomposite films are identified. The low-frequency shifts of C–H out-of-plane deformation vibrations of aromatic rings and the changes in characteristic band intensities of PPX are observed with increasing filler concentration. Additional IR-bands arise at 1000–1800 cm^–1 for PPX–PbS and PPX–CdS films and at 3100–3600 cm^–1 for PPX–CdS ones. However, the bands attributed to C–C and C–H stretch vibrations of the ring and С–Н deformation vibrations of СН₂-groups are found to lose much of their intensity in PPX–S films. The occurrence of complementary IR bands in nanocomposites is due to the formation of (1) complex sulfoxide phases with PbS nanoparticles, (2) C–O and C=O groups because of the oxidation of PPX polymer chains in the PPX–PbS films, and (3) complex compounds with sulfo (SO₄), hydroxyl (OH), and carboxylate (СОО^–) groups in the PPX–CdS films. Furthermore, some IR bands in PPX–PbS and PPX–CdS films are structural modifications of the substituted aromatic ring due to loss of symmetry.

The equation of state P(v/v_o) and the baric dependences of both the lattice and surface properties of germanium macro- and nanocrystals have been determined on the basis of the Mie–Lennard–Jones pairwise interatomic potential and the RP-model of a nanocrystal. It has been shown that the isothermal dependences P(v/v_o) of macro- and nanocrystals intersect each other at a certain value of the relative volume (v/v_o)₀. The surface pressure becomes zero at the intersection point (at (v/v_o)₀). The relative volume (v/v_o)₀ decreases with both an isomorphic–isomeric increase in the temperature and an isomorphic–isothermic decrease in the number of atoms in a nanocrystal or upon the isomeric–isothermic deviation of a nanocrystal from its energetically optimal shape (a cube for the RP-model). Based on the derived equation of state, the changes in 23 properties of germanium with both an isochoric (v/v_o = 1) and isobaric (P = 0) decrease in the number of atoms in a nanocrystal at temperatures of 100, 300, and 1000 K have been studied. It has been shown that the higher the temperature of a nanocrystal is, the greater the increase is in the specific volume of a germanium nanocrystal under an isobaric (P = 0) decrease in its size.

The paper studies transformations of the macromolecular structure of the polysaccharide arabinogalactan under the action of noble metal nanoparticles that form in its matrix during the formation of metal-containing nanobiocomposites. Exclusion liquid chromatography with complex trichannel detection was used to determine the molecular weight characteristics of arabinogalactan in the composition of metal–polymer nanocomposites self-organized via the specific interaction of the polysaccharide with the surface of zero-valent silver, gold, and platinum nanoparticles that form in an aqueous solution. Transmission electron microscopy was applied to determine the sizes of metal nanoparticles and the arabinogalactan macromolecule, which made it possible to classify the polysaccharide as nanoscale. It is shown that a change in the polydispersity of arabinogalactan occurs due to its redox interaction with noble metal ions and simultaneously due to the occurring alkaline destruction process. It was found that during alkaline depolymerization, which occurs in the synthesis of nanocomposites, the number average molecular weight of arabinogalactan decreases more significantly. The stabilization process for the growing nanoparticles in the formation of the dispersed phase, accompanied by the appearance of new bonds between the polysaccharide and the created in situ silver and gold nanoparticles, causes arabinogalactan macromolecules to aggregate.

Reverse microemulsions in the lecithin–oleic acid–paraffin oil–avocado oil–tea tree essential oil–water system and lamellar liquid crystals in the lecithin–avocado oil–tea tree essential oil–water system were studied as systems for transdermal drug delivery. Oil- and water-soluble substances, as well as substances that are poorly soluble in water and oil in the form of solid-phase particles, can be introduced into liquid crystals in concentrations of a few percent. Oil-soluble substances can be introduced into reverse microemulsions in concentrations of a few percent and water-soluble substances can be introduced in concentrations of tenths of a percent. The dialysis method showed that the rate of release of water-soluble substances from the reverse microemulsion containing 4.8 wt % water is approximately 2.5 times higher than that from the lamellar liquid crystal containing 15 wt % water. This is explained by the fact that the viscosity of liquid crystals is more than 100 times higher than the viscosity of microemulsions.

Transformation of the photoluminescence (PL) spectra of hybrid Si/SiO_x nanoparticles of the crystalline core–oxide shell type has been investigated in the temperature range of 10–320 K upon 325-nm laser excitation. Si/SiO_x nanoparticles are synthesized from silicon monoxide and functionalized in dimethyl sulfoxide (DMSO) or octadecene (OD). The PL spectra of the nanoparticles are considered as superpositions of short-wavelength (400–550 nm) and long-wavelength (600–900 nm) bands, which have significantly different ratios of the total intensities of these components in Si/SiO_x/OD and Si/SiO_x/DMSO samples. For Si/SiO_x/DMSO samples, the intensity of the short-wavelength band monotonically decreases with an increase in temperature from 10 K, whereas the intensity of the long-wavelength band first increases; however, then (at approximately 70 K) its slope begins to decrease and levels off. The specific features of the temperature dependence of the long-wavelength PL band intensity can be explained in this case by efficient energy transfer from defect oxygen-containing centers at the core boundary to exciton centers that arise under laser irradiation. In the case of Si/SiO_x/OD particles, for which the short-wavelength band intensity is initially low, this effect is not observed. For these particles, the influence of 405-nm cw laser radiation on the kinetics of changes in the intensity of the long-wavelength PL band has been studied beginning with a temperature of 10 K. It has been found that the PL intensity increases at temperatures near 10 K with an increase in the exposure time, which is explained by additional heating of nanoparticles in a vacuum.