No abstract

During the past few decades, hybrid nanoparticles (HNPs) based on a magnetic material and gold have attracted interest for applications in catalysis, diagnostics and nanomedicine. In this paper, magnetic CoFe2O4/Au HNPs with an average particle size of 20 nm, decorated with 2 nm gold clusters, were prepared using methionine as a reducer and an anchor between CoFe2O4 and gold. The methionine was used to grow the Au clusters to a solid gold shell (up to 10 gold deposition cycles). The obtained nanoparticles (NPs) were studied by X-Ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, X-Ray photoelectron spectroscopy (XPS) and UV-vis spectroscopy techniques. The TEM images of the obtained HNPs showed that the surface of cobalt ferrite was covered with gold nanoclusters, the size of which slightly increased with an increase in the number of gold deposition cycles (from 2.12 ± 0.15 nm after 1 cycle to 2.46 ± 0.13 nm after 10 cycles). The density of the Au clusters on the cobalt ferrite surface insignificantly decreased during repeated stages of gold deposition: 21.4 ± 2.7 Au NPs/CoFe2O4 NP after 1 cycle, 19.0 ± 1.2 after 6 cycles and 18.0 ± 1.4 after 10 cycles. The magnetic measurements showed that the obtained HNPs possessed typical ferrimagnetic behavior, which corresponds to that of CoFe2O4 nanoparticles. The toxicity evaluation of the synthesized HNPs on Chlorella vulgaris indicated that they can be applied to biomedical applications such as magnetic hyperthermia, photothermal therapy, drug delivery, bioimaging and biosensing.

In the current study, the effects of silver nanoparticles (AgNPs) synthesized under the action of “green” reagent glucose, on seed germination and seedling growth of wheat were investigated. Nanoparticles had a spherical shape and an average size of about 10 nm. Wheat seeds and seedlings were cultivated in Petri dishes for 3-7 days. After this, the number of germinated seeds, shoot and root fresh mass, and root length were measured. The results showed that the concentration range of 0.001-0.5 mg/L had no effect on seed germination, while the enhanced concentration induced an inhibitory effect. It was found that AgNPs had led to an increase in shoot and root fresh mass in the range of 0.06-1 mg/L and in the range of 0.03-0.1 mg/L, respectively. Beyond the concentrations up to 3 and 5 mg/L shoot and root fresh mass were inhibited respectively. Application of tested nanoparticles in the range of 0.005-0.5 mg/L caused an increase in root length of wheat. AgNPs at the concentration over 5 mg/L caused root length inhibition. The results show that AgNPs in the range of 0.06-0.5 mg/L may hold significant applications in agriculture and could provide as an alternative source of ecofriendly fertilizer for wheat.

Amethod is proposed for synthesizing copper ferrite, consisting in anion-exchange precipitation of copper (II) and iron (III) from solutions of their salts in the presence of tartrate ions as complexing agents followed by cal¬ cination of the obtained precipitate. The precursors and the products of their heat-treatment or studied by means of chemical, complex thermal and x-ray phase analyses, IR spectroscopy, scanning electron micro¬ scopy, and x-ray spectral microanalysis; the magnetic properties of the obtained samples were also studied. It was determined that a ferromagnetically ordered phase is present in the synthesized materials and their mag¬ netic properties are close to those of bulk CuFe 2 O 4 .

Construction and investment projects inherent risks in an extremely wide range of human activity fields. An analysis of risks from the viewpoint of management and mitigation is conducted in this article. Particular attention is paid to the analysis of risk events related to the choice of an unqualified contractors performing the job. The compliance of duration implementation project, the budget amount, and the quality of performed work depend on this choice. The contractors risk assessment methods analysis showed that besides the overall criterion for all methods connected to the cost of work it is vital to take into account the qualifications, reputation, material and technical base of a contractor, the time and quality of the work performed previously. Existing methods with criteria of the choice of contractors performing the job are considered. The universal methodology with a set of criteria that satisfies all construction process participants, and based on publicly accessible information about companies and their experience is essential.