Core-shell structured electrode materials for lithium ion batteries

Recent progress in studies of several types of core-shell structured electrode materials, including TiO₂/C, Si/C, Si/SiO _x , LiCoO₂/C, and LiFePO₄/C nanocomposites, including details of their preparation and their electrochemical performance is briefly reviewed. Results clearly show that the coating shell can effectively prevent the aggregation of the nanosized cores, which are the electrochemically active materials. In addition, the diffusion coefficients of lithium ions can be increased, and the reversibility of lithium intercalation and deintercalation is improved. As a result, the cycling behavior is greatly improved. The reviewed results suggest that core-shell nanocomposites are a good starting point for further development of new promising electrode materials.

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Chemistry,commentary and community: Discussion of “The NaDyBr<Subscript>4</Subscript> complex: its molecular structure and thermodynamic properties” by Varga and Hargittai

The molecular geometries, relative stabilities, binding energies, and dissociation energies of NaDyBr₄ and its molecular ion are discussed. Both the bidentate and tridentate isomers are stable for the neutral species, while only the bidentate form is stable for NaDyBr₄ ⁺.

Spectroelectrochemistry of intrinsically conducting furan-3-chlorothiophene copolymers

Electrochemical copolymerization of furan and 3-chlorothiophene was performed at constant electrode potential in a binary solvent system consisting of boron trifluoride diethyl etherate + ethyl ether (BFEE + EE; ratio 1:2) and trifluoroacetic acid (10% by volume). The homopolymers and copolymers obtained were studied with cyclic voltammetry, in situ ultraviolet–visible spectroscopy, in situ resonance Raman spectroscopy, and in situ conductivity measurements. The spectroelectrochemical properties of the copolymers show intermediate features between polyfuran and poly(3-chlorothiophene). The conductivity changes of homo- and copolymer films are almost completely reversible when the potential shift direction is reversed.

A comparative study of hydrothermal and sol–gel methods in the synthesis of MnO<Subscript>2</Subscript> nanostructures

In this work, MnO₂ nanostructure powders with different crystalline phases have been successfully prepared by hydrothermal and sol–gel methods. The obtained products were characterized by XRD and SEM techniques and their crystallographic phases and morphological properties compared. Results showed that α-MnO₂, β-MnO₂, and δ-MnO₂ nanorods were synthesized by hydrothermal method and γ-MnO₂ polymorph was obtained by sol–gel method.

Branched trichain sulfosuccinates as novel water in CO2 dispersants

A series of highly branched trichain sulfosuccinate surfactants have been synthesized and studied in condensed CO₂ and aqueous environments. Aqueous critical micelle concentrations (CMCs) showed a general trend of increasing CMC with decreasing chain length, whereas increased branching appeared to increase solubility in CO₂ and aid the dispersion of water. Near infrared spectra confirmed observed cloud with a large increase in solubility above the cloud pressures in this solvent.

Electrochemistry and catalytic behavior of immobilized binuclear complexes of copper(II) and nickel(II) with Robson type ligand

Various systems containing immobilized binuclear copper(II) and nickel(II) complexes with Robson type ligand ([M₂L]Cl₂) are studied and compared in relation to catalysis of hydrogen peroxide reduction. Molecular complexes adsorbed on mercury and gold, crystalline complexes immobilized in the carbon paste electrode, and complex species entrapped into polyphenol-modified gold electrodes are considered. Electrocatalysis is assumed to result from the formation of H₂O₂–[M₂L]Cl₂ adduct, not from mediating redox transformations. Possible geometry of the formed reaction layers supporting adduct formation is discussed.

Vapor phase tin diiodide: its structure and thermodynamics,a computational study

The molecular structure and vibrational characteristics of monomeric and dimeric tin diiodide, SnI₂ and Sn₂I₄, were determined by high-level computational methods. For the dimer molecule two low-energy geometries were found, one with C _s and the other with C _2v symmetry, the former with somewhat lower energy; their relative energy is strongly dependent on the computational method. Thermodynamic functions for both species and their dimerization reaction were calculated based on the computed structures.

Do we need to rethink collaborative trials?

The currently recommended design of collaborative trials (interlaboratory method performance studies) is examined in relation to the usefulness of the resulting statistics. It is suggested that larger experiments, without duplicate analysis, would be more informative.

Modeling of solvent viscosity effects on the electroreduction of Pt(II) aquachlorocomplexes

Solvent dynamics effects on the electroreduction of [PtCl₃(H₂O)]⁻ at a mercury electrode are explored in the framework of Sumi–Marcus model using an efficient computational scheme. According to results of density functional calculations, the second electron transfer step may be regarded as rate controlling. The nonmonotonous influence of solvent viscosity on the reaction rate is predicted and explained in terms of the saddle point avoidance. The results of model calculations are employed to interpret experimental data reported earlier in the literature.

A note on Michael Weisberg’s: challenges to the structural conception of chemical bonding

Michael Weisberg’s recent 2007 paper on the chemical bond makes the claim that the chemical notion of the covalent bond is in trouble. This note casts doubts on that claim.

Carbon–Carbon Bond Forming and Cleavage in the Reactions of Isopropenyl-acetylene and 2-Methyl-hex-1-en-3-yne with Fe3(CO)12 in Basic Methanolic Solution. The X-ray Structure of Fe2(CO)5[μ-η7-{RCC(H)C(CH3)CR}] (R=CH3(=CH2))

The title complex is the main product of the reaction of Fe₃(CO)₁₂ with isopropenylacetylene in basic methanolic solution (followed by acidification); it is obtained upon carbon–carbon bond forming and dimerization of the alkyne. The same complex is also obtained by reacting Fe₃(CO)₁₂ in CH₃OH/KOH solution with 2-methyl-hex-1-en-3-yne; carbon–carbon bond cleavage presumably occurs to form isopropenylacetylene, which then reacts with the iron carbonyl. The unprecedented structure of the complex has been determined with a X-ray diffraction analysis.

Encapsulating of single quantum dots into polymer particles

Single semiconductor quantum dots were embedded into polymer particles with diameters below 0.1 μm by an emulsion polymerization procedure or via a secondary dispersion approach. The photoluminescence properties of the nanocrystals are retained upon encapsulation, as demonstrated by fluorescence confocal microscopy.

Chemistry, commentary, and community: discussion of “an examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine” by Lipkind and Chickos

Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation techniques. It is suggested that pyridazine shows enigmatic behavior.

A novel Ce<Superscript>III</Superscript>-cyclam type complex and its redox chemistry in aqueous solutions

A new Ce^III complex was synthesized by mixing the ligand “dioxocyclam” with Ce^III ions at pH 8.0 and its redox properties were investigated.

Dimerization in Acetonitrile of [H6PMo9O34]3− into [P2Mo18O62]6−: Structural Characterization of the Tetrabutyl Ammonium Salt

The trivacant heteropolyanion A-α[PMo₉O₃₁(OH₂)₃]³⁻ spontaneously dimerizes in acetonitrile to form the Dawson complex [P₂Mo₁₈O₆₂]⁶⁻. A rapid new quantitative preparation of the sodium salt of this Dawson complex is described. In addition, the structure of TBA₅[HP₂Mo₁₈O₆₂] is given and the featuring data compared with the isomorphous sodium salt (space group C2/c).

Nanostructured SnO2-TiO2 films as related to lithium intercalation

The difference in degradation behavior of titania-doped tin dioxide films is explained by a pronounced effect of the doping level on the film dispersity and fine distribution of titania. A two to three times decrease in nanoparticles sizes in the doped films compared with nanoparticles in SnO₂ film (20–30 nm) is revealed by using scanning tunneling microscopy (STM). Such STM data (measured in ex situ configuration) combined with XRD and Mössbauer spectroscopy analysis confirm that the nanoparticles are composed of nanostructured heavily disordered SnO₂ and TiO₂ rutile solid solution or of amorphous phase containing both SnO₂ and TiO₂, the content of the crystalline and amorphous phases being approximately equal.

Properties of the electronic density of states in TiO<Subscript>2</Subscript> nanoparticles surrounded with aqueous electrolyte

Results on the density of sates of nanostructured TiO₂ as a function of particle size and temperature are reported. In TiO₂ nanoparticles with a mean diameter 10 nm, the density of states (DOS) is strongly temperature-dependent, indicating a rearrangement of the bandgap states in which the exponential energy parameter (width of the distribution) increases from 0.080 to 50 °C. For nanoparticles with mean diameters of 20 and 30 nm the DOS is much closer to an exponential distribution, and is much less sensitive to temperature variations. It is suggested that nanometer confinement has a significant influence on the density of electronic states for 10-nm particles, while band tailing is similar to that occurring in bulk semiconductors for the larger particles.

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Core-shell effects of functionalized oxide nanoparticles inside long-range meso-ordered spray-dried silica spheres

Core-shell and homogeneous distributions of functionalized cerium oxide nanoparticles within spray-dried mesostructured silica spheres are achieved by modification of synthesis parameters such as the templating agent and nanoparticle capping functions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Synthesis and dopamine receptor binding affinity of 4H-thiochromenoapomorphines

Abstract  The synthesis of 4H-thiochromene derivatives of apomorphines, a novel class of isoquinoline alkaloid-related compounds, has been achieved by different O-dealkylation methods applied on previously published heteroring-fused aporphinoids. Detailed DFT study has been presented regarding the mechanism of the L-selectride-mediated multiple O-dealkylation of a seven-ring aporphine analogue. Dopamine-binding tests confirmed the essential function of 11-hydroxy moiety of the aporphine skeleton and revealed a remarkable D₁ over D₂ specificity for the derivative having the 4H-thiochromene ring system attached to positions 2 and 3 of the aporphine backbone. Graphical Abstract  

Comparison of synthetic procedures for the preparation of sol–gel derived phenoxy-silica hybrid materials

Novel phenoxy-silica hybrid materials (with 3 wt.% SiO₂) have been synthesized using different synthetic procedures. Differential scanning calorimetric (DSC) (T_g), FT-IR and transmission electron microscopy (TEM) results, as well as thermal and mechanical properties, are reported for these hybrids, which can be classified into three different groups, depending on the number of components synthesized in situ. Best results in terms of homogeneity (TEM) and mechanical properties have been obtained when the sol–gel process has been carried out in the presence of a phenoxy resin modified with a pendant alkoxysilane monomer.