Topochemical Path in High Lithiation of MoS2

Lithiation of MoS₂/RGO (reduced graphite oxide) electrodes repeatedly reached experimental capacities larger than 1000 mA · g^–1, corresponding to at least 6 lithium equivalents per gram of MoS₂. At our best knowledge, a convincing explanation is still missing in literature. In most cases, phase separation into Li₂S and elemental Mo was assumed to occur. However, this can only explain capacities up to 669 mA · g^–1, corresponding to an exchange of four Li. Formation of LiMo alloys could resolve the problem but the Li/Mo system does not contain any binary phases. If signs for Li₂S formation were found, indeed experimental capacities were below 700 mAh · g^–1. Here we present a topochemical mechanism, which sustains multiple charge/discharge cycles at 1000 mAh · g^–1, corresponding to an exchange of at least 6 Li per formula unit MoS₂. This topochemical reaction route prevents decomposition into binary phases and thus avoids segregation of the components of MoS₂. Throughout the whole lithiation/delithiation process, distinct layers of Mo are preserved but extended or shrunk by slight movements and reshuffling of sulfur and lithium atoms. On addition of 6 Li per formula unit to MoS₂, all central sulfur atoms are hosted in mutual Mo–S layers such that formal S^2– and Mo^2– anions appear coordinated by lithium cations. Indeed, similar structures are known in the field of Zintl phases. Our first‐principles crystal structure prediction study describes this topological path through conversion reactions during the lithiation/delithiation processes. All optimized phases along the topological path exhibit a distinct Mo layering giving rise to a series of dominant scattering into pseudo 001 reflections perpendicular to these Mo planes. The mechanism we present here explains why such high capacities can be reached reversibly for MoS₂/RGO nano composites     

Ink‐Jet Printing of Electron Donor/Acceptor Blends: Towards Bulk Heterojunction Solar Cells

Summary: We illustrate the ink‐jet printing of a thin‐film library of donor/acceptor systems useful in bulk heterojunction solar cells and their characterization utilizing a UV‐vis/fluorescence plate reader and an optical profilometer. In addition, the morphology of the films has been examined by atomic force microscopy (AFM). The ink‐jet processing technology allows printing of arrays of different donor/acceptor compositions on one substrate as well as the subsequent fast optical screening of the electron transfer processes. The investigated films consist of blends of a poly(methyl methacrylate) polypyridyl ruthenium(II ) copolymer (RuPMMA) as electron donor material (p‐type) and C₆₀ fullerene (PC₆₀BM) as well as heptyl viologen (C₇‐V) derivatives as electron acceptor materials (n‐type).

Ink‐jet printing process and investigated donor/acceptor pair (RuPMMA‐PC₆₀BM).     

Ab-initio crystal structure prediction. A case study: NaBH4

Crystal structure prediction from first principles is still one of the most challenging and interesting issue in condensed matter science. we explored the potential energy surface of NaBH₄ by a combined ab-initio approach, based on global structure optimizations and quantum chemistry. In particular, we used simulated annealing (SA) and density functional theory (DFT) calculations. The methodology enabled the identification of several local minima, of which the global minimum corresponded to the tetragonal ground-state structure (P4₂/nmc), and the prediction of higher energy stable structures, among them a monoclinic (Pm) one was identified to be 22.75 kJ/mol above the ground-state at T=298 K. In between, orthorhombic and cubic structures were recovered, in particular those with Pnma and symmetries.     

Adsorption of light green and brilliant yellow anionic dyes using amino functionalized magnetic silica (Fe3O4@SiO2@NH2) nanocomposite

Abstract

Fe₃O₄@SiO₂@NH₂ nanocomposite was prepared for highly effective adsorption of two anionic dyes one of which is triarylmethane dye (light green, LG) and the other is azo dye (brilliant yellow, BY). The characterization results demonstrated that superparamagnetic Fe₃O₄ nanoparticles were covered with silica and functionalized with amino groups successfully without losing magnetic character. The effects of adsorbent dosage, contact time, pH, temperature, and dye molecular structure on the adsorption were investigated. Acidic pH was better for both LG and BY, on the other hand, alkaline pH was favorable to some extent for LG in comparison with BY due to the contribution of stacking effect in addition to electrostatic attraction. Kinetic data demonstrated that the driving force for adsorption process could be explained by pseudo-second order mechanism in both systems. The equilibrium data were more compatible with Langmuir isotherm than those of Freundlich isotherm and the maximum adsorption capacities of Fe₃O₄@SiO₂@NH₂ calculated from Langmuir isotherm model for LG and BY at 30?°C and natural pH of the solution were 40.2 and 35.5?mg g^?1. Thermodynamic calculations related to temperature dependence demonstrated that the adsorption process was spontaneous and exothermic.     

Synthesis of cis-1,2-diol-type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation

Two cis-1,2-diol-type chiral ligands (T ₁ and T ₂ ) and their tri-coordinated chiral dioxaborinane (T _(1–2) B _(1–2) ) and four-coordinated chiral dioxaborinane adducts with 4-tert-butyl pyridine sustained by N → B dative bonds (T _(1–2) B _(1–2) -N) were synthesized and characterized by various spectroscopic techniques such as NMR (¹H, ¹³C, and ¹¹B), FT-IR and UV–Vis spectroscopy, LC–MS/MS, and elemental analysis. It was suggested that both ferrocene and trifluoromethyl groups played key roles in the catalytic and biological studies because they could tune the solubility of the chiral dioxaborinane complexes and adjust the strength of intermolecular interactions. To assess the biological activities of newly synthesized chiral dioxaborinane compounds, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, reducing power, antibacterial, DNA binding, and DNA cleavage activities were tested. Then, all chiral dioxaborinane complexes were investigated as catalysts for the asymmetric transfer hydrogenation of various ketones under suitable conditions. The results indicated that the chiral dioxaborinane catalysts performed well with high yields.     

Light-emitting iridium(III) and ruthenium(II) polypyridyl complexes containing quadruple hydrogen-bonding moieties

A novel compound containing both a 2,2'-bipyridine as well as a 2-ureido-4[1H]-ureidopyrimidinone supramolecular moiety (3) has been synthesised and fully characterized by 1H-NMR, MALDI-TOFMS, UV-vis and IR spectroscopy. Subsequent coordination to iridium and ruthenium polypyridyl precursors allowed the formation of iridium(III) and ruthenium(II) polypyridyl dimers (5 and 7) assembled via quadruple hydrogen-bonding as well as metal coordination interactions. The syntheses and complete characterization of these materials by means of two-dimensional NMR techniques (1H-1H COSY and 1H-1H DOSY) as well as IR and MALDI-TOFMS are described in detail. Comparative studies of the optical properties of the luminescent model complexes (5' and '7) and the dimer species (5 and 7) are also illustrated. In addition, good processability of the materials has been demonstrated by inkjet printing leading to thin films revealing their potential for light-emitting devices.     

Green synthesis of silver nanoparticles by using eugenol and evaluation of antimicrobial potential

The importance of green synthesis was revealed with advantages such as: eliminating the use of expensive chemicals; consume less energy; and generate environmentally benign products. With this aim, silver nanoparticles (AgNPs) were synthesized by using isolated eugenol from clove extract. Its antimicrobial potential was determined on three different microorganisms. Clove was extracted and eugenol was isolated from this extract. Green synthesis was performed and an anti‐microbial study was performed. All extraction and isolation analyses were performed by high‐performance liquid chromatography (HPLC); identification and confirmation were achieved using liquid chromatography–mass spectrometry (LC–MS); and scanning electron microscopy was used for characterization. Both HPLC and LC–MS analyses showed that eugenol obtained purely synthesized AgNPs and 20‐25‐nm‐sized and homogeneous shaped particles seen in images. The antimicrobial effects of AgNPs at eight concentrations were determinated against Staphylococcus aureus, Escherichia coli and Candida albicans, and maximum inhibition zone diameters were found as 2.6 cm, 2.4 cm and 1.5 cm, respectively. The results of the antimicrobial study showed that eugenol as a biological material brought higher antimicrobial effect to AgNPs in comparison to the other materials found in the literature.     

Radioiodination and biodistribution of isolated lawsone compound from Lawsonia inermis (henna) leaves extract

Lawsonia inermis (henna) is one of the most effective medicinal plants and it has been using for treatment of wounds and burns for centuries. The using of Henna leaves is very popular for cosmetic as well as medicine in many countries. Henna leaves contain lots of different compounds and lawsone (LW) is the main one. In current study, extraction with bidistillated water of henna leaves was performed and LW was isolated by using high performance liquid chromatography system. Chemical structure of LW was evaluated by nuclear magnetic resonance method. LW was radiolabeled with iodine-131 (¹³¹I) radionuclide which is well known for nuclear imaging and therapy in nuclear medicine by utilizing iodogen method. The yield of radiolabeling of LW (¹³¹I-LW) was calculated as 92.70 ± 4.312 % (n = 10) by thin layer radio chromatography. Its in vivo biological activity was investigated by biodistribution studies which were performed by using healthy female and male Balb/C mice. According to results of biodistribution, uptake of ¹³¹I labeled LW compound in uterus, breast and ovary for female mice and prostate in male mice was higher than other organs in the body.     

The dynamical evolution of 3-space in a higher dimensional steady state universe

We investigate a class of cosmological solutions of Einstein’s field equations in higher dimensions with a cosmological constant and an ideal fluid matter distribution as a source. We discuss the dynamical evolution of the universe subject to two constraints that (i) the total volume scale factor of the universe is constant and (ii) the effective energy density is constant. We obtain various interesting new dynamics for the external space that yield a time varying deceleration parameter including oscillating cases when the flat/curved external and curved/flat internal spaces are considered. We also comment on how the universe would be conceived by an observer in four dimensions who is unaware of the extra dimensions.