Vol 64, No 14 (2019)

The literature on the manufacture and characterization of ZrB₂/HfB₂–SiC ultra-high temperature ceramics (UHTCs) modified by ultra-refractory carbides (ZrC, HfC, B₄C, TaC, VC, and WC) was analyzed. The specifics of various consolidation techniques are considered in the context of properties of the prepared samples. The role of these modifiers in the fabrication of UHTCs with improved characteristics was found to consist in grain growth inhibition and in scavenging oxide impurities, primarily ZrO₂/HfO₂, from the surfaces of metal diboride and silicon carbide particles. The role of additives on the oxidation resistance of the manufactured materials is discussed.

A method is proposed for obtaining glycine-based closo-decaborate anion derivatives containing a fluorescent group to study the distribution of potential BNCT agents.

The process for preparing SnO₂ nanocrystalline microspheres via synthesis in microemulsions combined with hydrothermal treatment of the resulting suspensions was studied. Tin acetylacetonate, whose n‑butanol solution is more convenient for use compared to classical reagents, was shown to have a promise for use as a precursor. Simultaneous thermal analysis and IR spectroscopy showed the transformation of a hydrated powder under heating to yield anhydrous tin dioxide. SEM analysis of the prepared SnO₂ powder microstructure elucidated a two-level organization of oxide particles—nanoparticles with a size of about 25 nm were hierarchically organized in the form of medium-sized microspheres of about 1.5 µm, were formed during microemulsion synthesis upon tin acetylacetonate hydrolysis.

A new mononuclear copper complex [Cu(dpq)(L–Met)Cl] ⋅ H₂O has been designed and synthesized using the phenanthroline derivative dipyridoquinoxaline (dpq). This complex has been characterized by element analysis and X-ray single crystal diffraction. The crystal structure of the complex belongs to a monoclinic system with space group C2/c. Binding of the complex to DNA has been investigated by absorption spectroscopy, fluorescence spectroscopy, and agarose gel electrophoresis. Spectrophotometric studies have showed that the mode of binding is intercalation with a binding constant K_b of 1.25 × 10³ L mol^–1. Additionally, the complex could quench an ethidium bromide-DNA complex. The apparent binding constant value for the complex is 1.89 × 10 ⁵ L mol^–1, which is slightly lower than the classical binding constant of 10⁷ L mol^–1. In addition, the quenching mechanism of the complex has been not static or dynamic. Agarose gel electrophoresis has shown that the complex cleaved circular pBR322 plasmid DNA to both nicked and linear forms; at higher concentrations and longer reaction times, the cutting results have been improved. The cleavage mechanism between the complex and plasmid DNA may involve singlet oxygen and hydroxyl radical as reactive oxygen species.

Being inert in the elemental state and as compounds, noble metals—ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, and gold—and rhenium, whose compounds have similar properties, form macrocyclic complexes with specific reactivity. This review highlights the achievements of the last two decades in the chemistry of complexes of these metals with porphyrins and some of their modified analogues. Emphasis is placed on the results of studies of approaches to synthesis and chemical, physical, electrochemical, electron-optical, magnetic, and catalytic properties of complexes as a theoretical basis for the practical application of compounds of this class in catalysis, photovoltaics, and medicine.

Compounds such as dioxygen dichloride (1), disulfur dichloride (2), and diselenium dichloride (3) have been investigated using LC-BLYP, LC-ωPBE and B3LYP with aug-cc-pVmZ basis set (m: 2, 3, 4). Natural Bond Orbital (NBO) analysis has been performed on skew (C₂), trans (C_2h) and cis (C_2v) conformations. The results indicated that the resonance energy associated with electron delocalization in molecules 1 to 3 in C₂ conformation is 13.75, 22.76, and 17.99 kcal/mol, respectively, and is directly related to the off-diagonal elements (F_ij). In addition, the Generalized Anomeric Effect (GAE) associated with electron delocalization is increased from molecules 1 to 2 and decreased from molecules 2 to 3.

The synthesis of thorium silicate (thorite) was carried out to characterize the parameters affecting the process. A synthetic thorite with formula ThSiO₄ was prepared by hydrothermal method with a mixture of 0.14 M thorium chloride (ThCl₄) solution and sodium silicate containing 0.14 M SiO₂. The effect of several experimental parameters on synthesis of thorite was investigated. The most important of these parameters were the pH of solution in hydrothermal process and volumetric ratio of SiO₂ : ThCl₄. The optimum pH in the hydrothermal process was 8–9, which was obtained by buffering with sodium bicarbonate. The increasing of volumetric ratio of SiO₂ : ThCl₄ led to gelatinization of synthetic material. The operating conditions of synthesis of thorite were determined as follows: volumetric ratio of SiO₂ : ThCl₄ = 0.9; pH after adding of 8 M NaOH, 8–8.5; pH after adding 0.5 M sodium bicarbonate, 8–9; temperature of heating in furnace, 250°C; time of heating in furnace, 24 h; pH after hydrothermal process, 8–9; temperature of drying in oven, 60°C; time of drying in oven, 24 h. In each batch of synthesis process, about 2.2 g or 7 mmol of thorium silicate was produced. The purity of thorite was determined 97.80%.

With the special focus to obtain a new tridentate ligand able to coordinate Fe(III), 3-hydroxy-2-(5'-hydroxypentyl)-4H-pyran-4-one (5-H) has been synthesized. Iron/ligand solution chemistry has been investigated in aqueous solution by ESI-MS and cyclic voltammetric measurements. The physiologic predominant specie is the tris-chelate complex as Job test attested. The electrode potential of the [Fe^III(5)₃]/[Fe^II(5)₃]^– couple was evaluated to be –0.54 V vs. SCE, pH 7.4.

Mg-doped ZnO nanoparticles with different contents of Mg dopant have been synthesized by tartaric acid complex method with subsequent calcination at 600°C for 2 h. The products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The analytical results have revealed the presence of wurtzite ZnO with hexagonal structure for undoped and Mg-doped samples with particle sizes of 100–200 nm for ZnO and 30–70 nm for 5 wt % Mg-doped ZnO. Visible light driven photocatalytic properties of ZnO and Mg-doped ZnO have been monitored through photodegradation of methylene blue (MB) identified by liquid chromatography-mass spectrometry (LC–MS). In this research, 5 wt % Mg-doped ZnO have shown the highest photocatalytic activity of 99% within 60 min.