Synthesis of the FePt nanosystem: comparison of the synthesis methods

In this work, using the example of the synthesis of nanoparticles of the mutual FePt system, obtained in an aqueous medium by the method of co-reduction of solutions of metal precursors, the effect of reducing agents is considered: an alkaline solution of hydrazine hydrate and sodium tetrahydroborate in combination with a stabilizer of sodium-potassium tartrate. The main characteristics of the obtained nanosized particles of the iron-platinum system were studied by means of a complex of physicochemical methods of analysis. The shape and morphology of the obtained nanosized particles were studied by transmission electron microscopy, phase analysis and X-ray structural parameters – by X-ray diffraction methods. It was approached to reveal the dependence of the particle size on the type of reducing agent used. It was found that nanosized FePt particles obtained with different reducing agents have similar physicochemical characteristics. The use of sodium tetrahydroborate, in the presence of a stabilizer sodium-potassium tartrate, allowed to obtain more dispersed particles with a size of 14.3±2.1 nm. FePt nanoparticles reduced by hydrazine hydrate were characterized by large sizes of 16.7±4.0 nm, and the particles form large dense agglomerates. Chemical analysis showed that when reducing with sodium tetrahydroborate, the target product contained 0.4 mol. % boron. When reducing FePt nanoparticles with hydrazine hydrate, it was found that the target product was contaminated with iron oxide, which was also confirmed by X-ray phase analysis. X-ray diffraction analysis showed that the iron-platinum nanosystem was represented by a solid-solution phase with a face-centred cubic lattice. The parameters of the crystal lattice were estimated, 3.908 Å and 3.894 Å, respectively, for FePt nanoparticles obtained using NaBH4 and N2H4∙H2O.

1,3-Dimethylbenzimidazolinium iodide and 1,3-dimethylbenzimidazoline in reduction processes of C=N group of imines

Interaction between 1,3-dimethylbenzimidazolinium iodide (as an analogue of 1,3-benzodithiolium and 1,3-benzothiolium and tropylium salts), aromatic Schiff bases, and sodium tetrahydroborate in tetrahydrofurane medium (in the presence of imidazole as a cation carrier, or without) at the ratio of starting reagents imine : 1,3-dimethylbenzimidazolinium iodide : sodium tetrahydroborate = 1:1:1 was studied. It was found out that, as basically distinct from the reaction of imines with analogues (1,3-benzodithiolium and 1,3-benzothiolium and tropylium salts) which, while reacting under similar conditions with Schiff bases, form accordingly the products of reductive heterylation – N-arylmethyl-4-(1,3-benzodithiol-2-il)aniline, or tropylation – N-arylmethyl-4-(7-cyclohepta-1,3,5-trienyl)aniline, whereas the reaction of imines with 1,3-dimethylbenz-imidazolinium iodide under similar conditions afforded N-arylmethylanilines in a high yield. This fact enables characterizing the 1,3-dimethylbenzimidazolinium iodide cation as more stable and less electrophilic due to an appreciable delocalization of a positive charge in the cation and, as a consequence, placing it as last (less reactive) in a series of known heteroanalogues (1,3-benzodithiolium > xanthilium > thioxanthilium > tropylium > N-methylacridinium > 1,3-dimethylbenzimidazolinium). The use of 1,3-dimethylbenzimidazoline as a donor of hydride-ion H (instead of sodium tetrahydroborate) also results in corresponding secondary aromatic amines as the reduction products of Schiff bases.

Analysis of methylmercury and total mercury in seafood using flow injection cold vapour atomic absorption spectrometry

Methylmercury and total mercury in sea food were analysed by flow injection cold vapour atomic absorption spectrometry using sodium tetrahydroborate as a reductant. Methylmercury in aquatic species was leached with HBr 47% as neutral MeHgBr complex and quantitatively extracted into toluene. MeHgBr in toluene was back extracted with L-cysteine into aqueous phase in form of negatively charged MeHg-L-cysteine complex. All organic compounds in the aqueous phase were decomposed with KMnO4/H2SO4 to convert methyl mercury to Hg2+ for direct cold vapour reaction. The seafood sample was digested with aquaregia for total mercury analysis. The limits of detection/quantitation for methylmercury and total mercury were là 0.69/1.3 ng/g and 0.70/2.2 ng/g (as Hg), respectively. The recovery of the analytical methods for MeHg and total Hg were 96.5–105% and 93–101% within the concentration ranges of 2–700 ng/g Hg. The concentrations of MeHg and total Hg in some common seafood such as fish, shrimp and squid were in ranges of 1.2–483.5 ng/g and 4.0 ÷ 663.4 ng/g.

SYNTHESIS OF BIOLOGICALLY ACTIVE COPPER SOLS IN PRESENCE OF NITRILOTRI(METHYLENE)PHOSPHONIC ACID

In this work the conditions for synthesis of copper nanoparticles by sodium tetrahydroborate in the presence of NTF are optimized. It is proved that the most favorable conditions for the reduction of copper in the solutions with its concentration of 2.0∙10-2 mol/l, are created when the concentration of tetrahydroborate sodium is three to four- fold exceeded, the titratable alkalinity is 5.3∙10-2-10.3∙10-2 mol/l, the temperature is 60 °C and the ratio of cation and chelate is equimolar. The method of photon correlation spectroscopy has confirmed the obtaining of copper nanoparticles with hydrodynamic radius of 25 nm, including shell stabilizers. The immutability of the size of bass for at least 72 h has been revealed.