Theory and practice of a powerful technique for electrochemical investigation of solid solution electrode materials

The theory and practice of a solid-state electrochemical technique which allows measurement of the chemical diffusion coefficient and partial conductivities of the mobile species in a mixed ionic-electronic conductor, as well as the equilibrium partial thermodynamic quantities, are described. The theory incorporates nonideal thermodynamic behavior of the carriers as well as cross terms in the flux equations. Once the cell is assembled, all parameters can be measured as a function of composition without any further physical manipulation, so that the experiments are well suited to automatic control.     

A chromium catalyst for the polymerization of ethylene as a homogeneous model for the phillips catalyst

A structurally characterized cationic chromium(III) alkyl featuring a bulky nacnac ligand catalyzes the polymerization of ethylene as well as the copolymerization of ethylene with alpha-olefins. This well-characterized homogeneous catalyst constitutes a structural as well as functional model of the widely used heterogeneous Phillips olefin polymerization catalyst.     

Trapping of a particle in a short-range harmonic potential well

Eigenstates of a particle in a localized and unconfined harmonic potential well are investigated. Effects due to the variation of the potential parameters as well as certain results from asymptotic expansions are discussed.     

Chemoselective synthesis of multiple epoxy-bridged tetrahydropyranone ring systems

Bis- as well as tris-tetrahydropyranone ring systems were obtained via multiple tandem cyclization-1,3-dipolar cycloaddition reactions of α-diazo ketones with ketone as well as aldehyde functional groups in a chemoselective manner.     

Metal On‐Line Voltammetric Analyzer for On‐Site Monitoring of Iron Speciation in Acid Mine Drainage Waters: Development and Characterization

The development of a simple, low cost, portable metal on‐line voltammetric analyzer (MOVA) for the iron analysis, as well as other species, in mining effluents is presented. It consists of a voltammetric cell based on an impinging jet flow configuration, a fluidic system controlled by gravity and electronics. Laboratory tests were performed to optimize the system as well as the analytical conditions for Fe speciation measurements. MOVA was then tested in the laboratory, in samples of both mining effluents. The results showed that iron in both mining effluents, as well as copper and arsenic, can be measured in oxygenated samples.     

Two-mode Fluorescent Detection of Cyanide by a Simple AIE-based Chemosensor with Red Emission

TPE-TCF, a simple TPE-derivative with red-emission was used to detect cyanide in the condition of single dispersion as well as under aggregate state. It could be found that TPE-TCF exhibited excellent fluorescent response to cyanide in both situations, and the mechanism was supposed to be the reaction between cyanide and the double bond in TPE-TCF as well as the aggregation induced emission property of the reacted TPE-TCF molecules. What's more, TPE-TCF could distinguish cyanide with other species, such as common anions and biotiol well, which indicated it as a potential indicator for cyanide with good selectivity and specificity.     

Solid-phase synthesis of lipidated peptides

Characteristic partial structures of lipidated proteins embodying different lipid groups as well as additional fluorescent tags or a maleimide for coupling to proteins can be synthesized readily by means of a new solid-phase technique employing the oxidative cleavage of the hydrazide linker as well as on-resin farnesylation and palmitoylation after appropriate deprotection of cysteine thiol groups as the key steps.     

Aspects of Electrochemical Behavior of Aldehydes and Ketones in Protic Media

Reduction of carbonyl group in aldehydes and ketones, as well as oxidation of numerous aldehydes is discussed, as well as those reductions of organic compounds where the C?O group activates cleavage of an adjacent C? X bond where X is a good leaving group like halogen, OH, NH₂ or SR or activates hydrogenation of an adjacent C?C group. Survey involves aliphatic and aromatic aldehydes, aryl alkyl and diaryl ketones, as well as α‐ketoacids, 1,2‐diketones and compounds where the carbonyl group is a part of a ring. The role of acid–base, hydration–dehydration and in some cases keto–enol equilibria on electrochemical behavior is pointed out, as well as the role of buffer kind and concentration and the nature of the cation of supporting electrolyte. Better understanding of these factors promises finding of best conditions for electroanalytical procedures.     

基于杯芳烃主体的分子自组装研究进展

分子自组装是超分子化学最重要的研究内容之一. 杯芳烃作为继冠醚、环糊精之后的第三代人工合成受体分子已在分子自组装研究方面取得了重要进展并显示了广泛的应用前景. 主要综述杯芳烃衍生物通过氢键、金属诱导配位、π-π作用、疏水作用等非共价键弱相互作用力在溶液状态、固态和界面的分子自组装方面的研究进展.     

Colloid-colloid and colloid-wall interactions in driven suspensions

We investigate the nonequilibrium fluid structure mediated forces between two colloids driven through a suspension of mutually noninteracting Brownian particles as well as between a colloid and a wall in stationary situations. We solve the Smoluchowski equation in bispherical coordinates as well as with a method of reflections, both in linear approximation for small velocities and numerically for intermediate velocities, and we compare the results to a superposition approximation considered previously. In particular, we find an enhancement of the friction (compared to the friction on an isolated particle) for two colloids driven side by side as well as for a colloid traveling along a wall. The friction on tailgating colloids is reduced. Colloids traveling side-by-side experience a solute induced repulsion while tailgating colloids are attracted to each other.     

Investigations on the behaviour of acidic, basic and neutral compounds in capillary electrochromatography on a mixed-mode stationary phase

This work describes the separation of acidic, basic and neutral organic compounds as well as inorganic anions in a single run by capillary electrochromatography employing a stationary phase which exhibits both strong anion-exchange and reversed-phase chromatographic characteristics. The positive surface charge of this stationary phase provided a substantial anodic electroosmotic flow. The analytes were separated by a mixed-mode mechanism which comprised chromatographic interactions (hydrophobic interactions, ion-exchange) as well as electrophoretic migration. The influence of ion-exchange and hydrophobic interactions on the retention/migration of the analytes could be manipulated by varying the concentration of a competing ion and/or the amount of organic modifier present in the background electrolyte. Additionally the effects of pH changes on both the chromatographic interactions as well as the electrophoretic migration of the analytes were investigated.     

“Green Is the Color”: An Update on Ecofriendly Aspects of Organoselenium Chemistry

Organoselenium compounds have been successfully applied in biological, medicinal and material sciences, as well as a powerful tool for modern organic synthesis, attracting the attention of the scientific community. This great success is mainly due to the breaking of paradigm demonstrated by innumerous works, that the selenium compounds were toxic and would have a potential impact on the environment. In this update review, we highlight the relevance of these compounds in several fields of research as well as the possibility to synthesize them through more environmentally sustainable methodologies, involving catalytic processes, flow chemistry, electrosynthesis, as well as by the use of alternative energy sources, including mechanochemical, photochemistry, sonochemical and microwave irradiation.     

Liquid crystalline materials for light-emitting diodes

Liquid crystalline materials display unique properties which can be exploited in organic light-emitting diodes. Characteristic features of liquid crystals are the anisotropy of electronic properties, a strong coupling to external fields as well as a tendency to form spontaneously homogeneous monodomain films. It is found that liquid crystalline materials can be used in light-emitting diodes to control the state of polarization of the emitted light, the magnitude of the onset field for emission as well as the quantum efficiency. Both low molar mass and polymeric liquid crystals have been introduced with great success in single as well as in multilayer devices. © 1998 John Wiley & Sons, Ltd.     

Advances and challenges of MOF derived carbon-based electrocatalysts and photocatalyst for water splitting: A review

Environmental pollution and energy shortage are substantial fears to the modern world's long-term sustainability. Water splitting is an essential technique for eco - friendly and sustainable energy storage, as well as a pollution-free method to produce hydrogen. In this regards Metal–organic frameworks have emerged as the most competent multifunctional materials in recent times, due to its large surface areas, adjustable permeability, easy compositional alteration, and capability for usage as precursors with a wide range of morphological forms. Further, MOF-derived carbon-based nanomaterials also offer significant benefits in terms of tunable morphological features and hierarchical permeability, as well as ease of functionalization, making them extremely effective as catalysts or catalysts supports for a wide variety of important reactions. Recent developments in carbon-based MOFs as catalysts for overall water splitting are discussed in this review. We explore how MOFs and carbon-based MOFs might well be beneficial, as well as which methods should be explored for future development. We divided our review into two sections: photocatalytic and electrocatalytic water splitting, and we gathered published literature on carbon-based MOFs materials for their outstanding activity, offers helpful methods for catalysts design and analysis, as well as difficulties This study highlights the developments in MOF derived materials as photo and electro catalysts by explaining respective approaches for their use in overall water splitting.     

THE VISUAL PROCESS: PHOTOPHYSICS and PHOTOISOMERIZATION OF MODEL VISUAL PIGMENTS and THE PRIMARY REACTION

Abstract— A systematic comprehensive consideration of the emission spectroscopy, emission lifetimes, transient spectroscopy, as well as quantum yields of fluorescence, triplet occupation and photoisomeriz-ation is given for a wide variety of polyene derivatives including retinyl and longer, as well as shorter chainlength homologs. Absorption spectral properties and the results and significance of theoretical calculations are also included. Chainlength, solvent and temperature effects on state order and photophysical as well as photoisomerization properties are evaluated. The mechanism for the primary light step in vision is considered in light of photophysical and photoisomerization data on model visual pigments and rhodopsin.     

Aligned Carbon Nanotube Stationary Phases for Electrochromatographic Chip Separations

This paper reports a novel approach for developing a microfluidic electrochromatographic chip device using patterned vertically aligned carbon nanotubes as the stationary phase material. Patterned growth of nanotubes in a specific location of the channel is carried out using a solid phase Fe–Al catalyst as well as a vapor deposited ferrocene catalyst. Proof-of-concept applications are demonstrated using reversed phase capillary electrochromatographic separations as well as solid phase extraction of a glycosylated protein using concanavalin A immobilized onto the nanotube bed.     

Spektrochemische schnellbestimmung einiger spurenelemente in der kohlenasche mit alumininmelektroden und verwendung des sichtbaren spektralgebietes

Using an a.c. arc and visible spectral lines a spectrographic method for the rapid determination of traces of Co, Cr, Ga.In, Pb and V in synthetic coal ashes has been worked out, in which the samples are burned in Al electrodes thus avoiding perturbation by cyanogen bands. With the help of intensity-time studies an exposure time of 10 sec was found giving optimum power of detection as well as optimum reproducibility. By a suitable choice of experimental conditions the background density was adjusted to a value which permitted making accurate background corrections and using the background as reference radiation at the same time. Variation of the method included the application of intermediate diaphragms and the use of Fe-lines as well as of the background as reference signals with and without background correction. The standard deviations as well as the tested concentration ranges are reported.     

Unterscheidung von Humins?uren und Ligninsulfons?uren durch zeitaufgel?ste Untergrundsignale in der Graphitrohr-AAS (Graphitrohr-Pyrolyse, UV-Pyrolyse-Spektrometrie)

Summary The computer-time-resolved background measurement in electrothermal AAS (graphite tube-AAS) is employed in order to achieve a differentiation in the substances of organic materials as well as a summary classification by pyrolytic behaviour. By way of example of various humic acids as well as lignin-sulphonic acid the differences in pyrolytic behaviour in UV gas-phase spectrometry is shown.     

Coriolis coupling effects in the dynamics of deep well reactions: application to the H(+) + D2 reaction

We present exact and estimated quantum differential and integral cross sections as well as product state distributions for the title reaction. We employ a time-dependent wavepacket method including all Coriolis couplings and also an adapted code where the helicity quantum number and with this the Coriolis couplings have been truncated. Results from helicity truncated as well as helicity conserving (HC) calculation are presented. The HC calculations fail to reproduce the exact results due to the influence of the centrifugal barrier. While the truncated calculation overestimate the exact integral cross sections they reproduce the features of the integral cross section very well. We also find that the product rotational state distributions are well reproduced if the maximum helicity state is chosen carefully. The helicity truncated calculations fail to give a good approximation of differential cross sections.     

Synthesis of block and graft copolymers of tetrahydrofuran and cyclic acetals

The polymerization of tetrahydrofuran under a living form allows quantitative functionalisation as well as the formation of copolymers. Cyclic acetal polymerization is more complex but through the “Activated-Monomer Mechanism” approach, it is possible to prepare telechelic polymers as well as block and graft copolymers with particular emphasis concerning amphiphilic ones.