Vol 12, No 9-10 (2017)

This work aims to explore the effect of polyelectrolyte layers on the protein adsorption using the example horseradish peroxidase (HRP) in a glass multicapillary to develop ways to control the selective sorption. It is shown that a more effective adsorption of HRP was observed for the bilayer polyethylene (PEI)/polystyrene sulfonate (PSS). This effect is explained by the fact that the polycation PEI modifies the glass surface, and the polyanion PSS creates a layer for the HRP effective sorption.

SERS tags are a new class of nanoprobes consisting of metal nanoparticles with adsorbed Raman active molecules. The brightness of a single tag depends on the Raman cross section of the reporter molecules and on the enhancing properties of plasmonic particles. Here, nine types of composite AuNR(core, 81 × 25 nm)@R@Ag(shell, 14 nm) nanorods (NRs) with thiolated aromatic molecules (R, nine different molecules) embedded between metal layers were synthesized. The Raman efficiency of reporters was evaluated by measuring normal Raman spectra in ethanol. The surface-enhanced Raman scattering (SERS) was evaluated for molecules adsorbed on Au nanorods before and after Ag shell growth. The coverage of the functionalized Au nanorods with an Ag shell results in an increase in SERS enhancement factor by two orders of magnitude, from 2.5 × 10⁴ for the initial Au NRs to 8.5 × 10⁶ for composite particles. Finite-difference time-domain (FDTD) simulations showed that the ultrahigh enhancement of Raman scattering inside composite nanorods can be explained by the enhancement of the EM field at the boundary of metal layers. Thus, for fabricated composite particles, we have a specific variant of EM SERS enhancement at the boundary of Au/Ag metals, which is different from the local field enhancement near plasmonic particles.

Materials with a NASICON structure having the composition (NH₄)_1−xH_xHf₂(PO₄)₃ (x = 0–1) have been obtained by hydrothermal synthesis followed by heat treatment and by ion exchange and characterized by X-ray powder diffraction, low-temperature nitrogen adsorption, and scanning electron microscopy. The catalytic activity of the materials in the conversion of ethanol is studied. All synthesized samples are shown to exhibit activity in the dehydration of ethanol and, to a small extent, the dehydrogenation of ethanol. At low temperatures, the conversion of ethanol predominantly results in the formation of diethyl ether and, at higher temperatures, the reaction predominantly affords ethylene. The selectivity in diethyl ether formation reaches 96% with 60% conversion at 360°C on the ion exchange–produced material of HHf₂(PO₄)₃ composition with a triclinic modification. At temperatures ≥450°C, the selective formation of ethylene is observed almost on all materials (~100%, with 100% conversion on NH₄Hf₂(PO₄)₃ with a rhombohedral modification at 450°C).

The dielectric characteristics of hafnia thin films deposited by the DC reactive magnetron sputtering of a Hf target in an Ar/O₂ gas mixture without heating the substrates have been studied. The permittivity, dielectric loss tangent, band gap, and leakage current density are obtained as functions of the oxygen content in an Ar/O₂ gas mixture upon film deposition. As is established, hafnia thin films with good dielectric characteristics are formed in a relatively wide range of oxygen concentrations (about 12–20% O₂). Without heating the substrates and subsequent annealing, the films possess permittivity ε = 17–22, a loss tangent of 0.03–0.05, and leakage currents density of 10⁻³ A/cm at E = 5 × 10⁵ V/cm; the optical band-gap width of the deposited films is found to be 5.7–5.8 eV.

The dependence of the effect of time delay at a constant maximum temperature on the physicomechanical parameters of the sintered sample has been considered. Based on the results of the work, it can be concluded that it is necessary to reduce the duration of all sections of the sintering process in order to exclude the recrystallization factor, which worsens the parameters of the ceramics.

An antimicrobial composite—selenium nanoparticles encapsulated in a biogeneous matrix consisting of arabinogalactan from Larix sibirica—has been developed and characterized. The effect of a novel selenium-containing nanocomposite on bacterial phytopathogen Clavibacter michiganensis ssp. sepedonicus (inducing ring rot disease of potato) is studied. It is shown that the complex of arabinogalactan and nanoselenium has a bactericidal effect, and its application leads to the morphology changes of bacterial cells and their death after 24 h of incubation.

The different forms of selenium nanoparticles include the least studied ones, both as a biofortification tool and in regards to the question of the mechanism of their accumulation. The effect of selenium nanoparticles and ionic forms of selenium on the growth and biochemical characteristics of male and female spinach plants are investigated. General properties typical both for nanoparticles and ionic forms of the element include a more intensive accumulation of selenium by male spinach forms, an increase in nitrate content in male plants and a decrease in female individuals, and the predominant accumulation of polyphenols by male forms. The effect of significant differences of nanoparticles and ionic selenium forms was demonstrated on the higher growth-promoting effect of nanoparticles when compared to selenate and selenite. The selenium fortification level decreased in the following way: selenate > nanoparticles of selenium > selenite. Differences between male and female accumulations of selenium are the largest for selenium nanoparticles and the lowest for selenate application. The increase in accumulation of ascorbic acid due to selenium biofortification is the least expressed for selenium nanoparticles. Contrary to ionic forms of selenium, nanoparticles maximally decrease the level of cadmium in female individuals. The results suggest the possibility of the participation of phytohormones (cytokinins and gibberellins) in the accumulation of selenium nanoparticles/ ionic forms and changes in biochemical characteristics of spinach plants as a result of biofortification.