On the Quantum Chemical Nature of Lead(II) “Lone Pair”

We study the quantum chemical nature of the Lead(II) valence basins, sometimes called the lead “lone pair”. Using various chemical interpretation tools, such as molecular orbital analysis, natural bond orbitals (NBO), natural population analysis (NPA) and electron localization function (ELF) topological analysis, we study a variety of Lead(II) complexes. A careful analysis of the results shows that the optimal structures of the lead complexes are only governed by the 6s and 6p subshells, whereas no involvement of the 5d orbitals is found. Similarly, we do not find any significant contribution of the 6d. Therefore, the Pb(II) complexation with its ligand can be explained through the interaction of the 6s2 electrons and the accepting 6p orbitals. We detail the potential structural and dynamical consequences of such electronic structure organization of the Pb (II) valence domain.

SEPARATION OF OIL-WATER EMULSIONS

Одним из наиболее серьёзных осложнений при добыче и транспортировке нефти является интенсивное выпадение асфальто-смолистых и парафиновых отложений (АСПО). В данной работе проводилась оценка эффективности растворителей разной химической природы для удаления АСПО. На основании лабораторных данных были сделаны выводы о использовании неиногенного типа ПАВ, спиртов с различной молекулярной массой, оптимального соотношения алканового и ароматического компонента для растворения АСПО парафинового типа. One of the most serious complications in oil production and transportation is the intensive deposition of as-falto-resinous and paraffin deposits (ASPs). In this work, the effectiveness of solvents of different chemical nature for the removal of ASPs was evaluated. Based on laboratory data, conclusions were drawn about the use of noninogenic surfactants, alcohols with different molecular weights, and the optimal ratio of the alkane and aromatic components for the dissolution of paraffin-type ASPs.

Real-Time Electrical Conductivity Monitoring and Correlation with Sulfate Release and Acid Mine Drainage Potential from a Gold/Silver Paste Tailing Storage

Safe disposal of tailings as high-density thickened tailings or paste tailings can reduce the environmental risks of conventional tailings deposits, reduce water use, minimize tailings storage facility footprints, reduce the potential for acid mine drainage (AMD), and minimize risks of failure, among other advantages. In the dewatering process, the addition of flocculants is key to improving the sedimentation of the tailings and the formation of a compact paste. Despite the environmental and operational advantages of using paste tailings, it is not clear how the chemical nature of coagulants and flocculants could influence the discharge of toxic elements (salts and metals) from tailings after storage. In this study, we show the results of the real-time evaluation of the release of polluting runoffs from a paste tailings deposit. To do this, we analyzed paste tailing samples for AMD potential through static and kinetic tests and monitored the electrical conductivity and real-time pH, evaluating the correlation with the sulfate in the thickener and downstream from the tailings deposit. Tailing samples have low sulfur content (<2%) and low acid-generating potential. Moreover, there is no evidence of a significant positive correlation (Pearson’s coefficient r < 0.8) between the sulfate concentrations with the pH or EC. Thus, the chemical nature of the paste tailings prior to discharge has no direct impact on the release of sulfate-rich runoffs from the tailings after its storage. This indicates that the tailings paste at the evaluated site is chemically stable in the short term.

Lipid-Based Nanovesicular Drug Delivery Systems

In designing a new drug, considering the preferred route of administration, various requirements must be fulfilled. Active molecules pharmacokinetics should be reliable with a valuable drug profile as well as well-tolerated. Over the past 20 years, nanotechnologies have provided alternative and complementary solutions to those of an exclusively pharmaceutical chemical nature since scientists and clinicians invested in the optimization of materials and methods capable of regulating effective drug delivery at the nanometer scale. Among the many drug delivery carriers, lipid nano vesicular ones successfully support clinical candidates approaching such problems as insolubility, biodegradation, and difficulty in overcoming the skin and biological barriers such as the blood–brain one. In this review, the authors discussed the structure, the biochemical composition, and the drug delivery applications of lipid nanovesicular carriers, namely, niosomes, proniosomes, ethosomes, transferosomes, pharmacosomes, ufasomes, phytosomes, catanionic vesicles, and extracellular vesicles.

SURFACE LUMINESCENCE OF A2B6 SEMICONDUCTOR QUANTUM DOTS (REVIEW)

Semiconductor zero-dimensional nanocrystals – quantum dots (QDs) – have been increasingly used in various fields of opto- and nanoelectronics in recent decades. This is because of the exciton nature of their luminescence, which can be controlled via the well known quantum-dimensional effect. At the same time, at small nanocrystall sizes, the influence of the surface on the optical and structural properties of nanocrystals increases significantly. The presence of broken bonds of surface atoms and point defects – vacancies and interstial atoms – can both weaken the exciton luminescence and create new effective channels of radiant luminescence. In some cases, these surface luminescence becomes dominant, leading to optical spectra broadening up to the quasi-white light. The nature of such localized states often remains unestablished due to the large number of the possible sorts of defects in both of QD and its surrounding. In contrast to exciton luminescence, which can be properly described within effective-mass approximations, the optical properties of defects relay on chemical nature of both defect itsself and its surrounding, what cannot be provided by “hydrogen-type coulomb defect” approximation. Moreover, charge state and related to this lattice relaxation must be taken into account, what requires an application of atomistic approach, such as Density functioal theory (DFT). Therefore, this review is devoted to the study of surface (defect) states and related luminescence, as well as the analysis of possible defects in nanocrystals of semiconductor compounds A2B6 (CdS, CdZnS, ZnS), responsible for luminescence processes, within ab initio approach. The review presents the results of the authors' and literature sources devoted to the study of the luminescent characteristics of ultra-small (<2 nm) QDs.

A Review on Synthesis, Properties, of Liquid Crystal Dendrimers

This review provides brief information concerning with the dendrimer. The supramolecular organization of selected examples of liquid-crystalline dendrimers within lamellar, columnar and nematic phases is reported. It is shown that tuning of the mesomorphic structure can be achieved by an appropriate molecular design depending upon the chemical nature of the terminal mesogenic groups, dendritic core and dendrimer generation. The pseudospherical shape of a dendrimer arises from its structure, which consists of an internal region (the core) which is connected to repeating units constituting a radial branching pattern.

SEIXOS DE FOSFATOS-SULFATOS DOS MINERAIS DO SUPERGRUPO ALUNITA NOS ALUVIÕES DIAMANTÍFEROS DE PAININN ÀS MARGENS DO TAPAJÓS EM ITAITUBA (PARÁ): GOYAZITA-FLORENCITA-GORCEIXITA-CRANDALLITA-ESVANBERGITA/WOODHOUSEITA

The diamond alluvium gravels from the Painin garimpos, on the right bank of the Tapajós River, in Itaituba, Pará, stand out for the marked presence of pebbles from <1 cm to about 10 cm in diameter consisting of aluminum phosphate-sulfates (APS minerals) from the alunite supergroup: goyazite-florencite-gorceixite-crandallite-esvanbergite/woodhouseite. They are light gray pebbles, still containing small amounts of pyrite, kaolinite, goethite and anatase. The total chemical and trace element analyzes confirm the indicated mineralogical constitution alongside the XRD. The florencite member is mainly dominated by Ce, La, Nd and Sm, the light rare earth elements, and also contains anomalous concentrations of Nb, Y, Pb, U and Th. This chemical nature of these pebbles, in part, makes it possible to compare them with the diamond satellite beans (favas) in secondary deposits in Brazil, but chemically only with the phosphates from Malawi and Sayan.

Anti-inflammatory effect of gold nanoparticles supported on metal oxides

Gold (Au) can be deposited as nanoparticles (NPs) smaller than 10 nm in diameter on a variety of metal oxide (MOx) NPs. Au/MOx have high catalytic performance and selective oxidation capacity which could have implications in terms of biological activity, and more specifically in modulation of the inflammatory reaction. Therefore, the aim of this study was to examine the effect of Au/TiO2, Au/ZrO2 and Au/CeO2 on viability, phagocytic capacity and inflammatory profile (TNF-α and IL-1β secretion) of murine macrophages. The most important result of this study is an anti-inflammatory effect of Au/MOx depending on the MOx nature with particle internalization and no alteration of cell viability and phagocytosis. The effect was dependent on the MOx NPs chemical nature (Au/TiO2 > Au/ZrO2 > Au/CeO2 if we consider the number of cytokines whose concentration was reduced by the NPs), and on the inflammatory mediator considered. The effect of Au/TiO2 NPs was not related to Au NPs size (at least in the case of Au/TiO2 NPs in the range of 3–8 nm). To the best of our knowledge, this is the first demonstration of an anti-inflammatory effect of Au/MOx.

FEATURES OF IN SITU FORMATION OF MIXTURES OF LINEAR POLYMERS

This article is devoted to the analysis of the results of the investigation of the process of forming mixtures of linear polymers formed simultaneously in situ according to different mechanisms. The first mechanism is polyaddition, the second mechanism is radical polymerization. This is one of the possible ways to obtain multicomponent polymer systems. The kinetics of chemical reactions of the formation of components and the phase separation which accompanies these reactions were studied for mixtures of poly(methyl methacrylate) (PMMA) with two polyurethanes (PU) of different chemical nature of both flexible and rigid blocks. PU-1 was synthesized from macrodiisocyanate based on oligo(tetramethylene glycol) with molecular mass 1000 g·mol–1 and hexamethylene diisocyanate taken in the molar ratio 1 : 2 using diethylene glycol as a chain extender. PU-2 was synthesized from macrodiisocyanate based on olygo(propylene glycol) with molecular mass 1000 g·mol–1 and toluylene diisocyanate taken in the molar ratio 1 : 2 using butanediol as a chain extender. The mixture of polystyrene (PS) with PU-2 was studied too. It is established that regardless of the chemical nature of the components, the process of in situ mixture formation is subject to general laws. In particular, the change in the chemical nature of the component formed by the mechanism of polyaddition (mixtures PMMA/PU-1 and PMMA/PU-2) or of the component formed by radical polymerization (mixtures PMMA/PU-2 and PS/PU-2) does not affect the nature of the dependence of the conversion degree of components and the fraction of formed polymers at the beginning of the phase separation on the composition of the initial reaction mixtures. Only the absolute values of these parameters change due to different reactivity and different thermodynamic compatibility of the mixed components.