Inhibition of LaNi5 electrode decay in alkaline medium by electroless encapsulation of active powder particles

Surface of powdered LaNi₅ intermetallic compound has been modified by active particle coverage with electroless nickel (Ni-P). The electrode degradation process in 6 M KOH solution has been tested across 70 charge/discharge cycles at −0.5 C/+0.5 C rates. It has been established that after approx. 25–35 initial cycles, the electrode degradation process fulfills first order chemical reaction kinetics law: logarithm of discharge capacity linearly decreases with cycle number. The rate constant for the Ni-P protected material is over 20 % lower than that of as received one. The surface modification also improves the alloy hydrogenation kinetics: exchange current densities of H₂O/H₂ system are generally greater for modified material and, contrary to uncovered material, do not practically decrease with long-lasting cycling.

     

Characterization of ion transport property in hot-press cast solid polymer electrolyte (SPE) films: [PEO: Zn(CF3SO3)2]

Characterization of ion transport property in dry solid polymer electrolyte (SPE) films: [PEO: Zn(CF₃SO₃)₂] in different salt wt% ratio has been reported. SPE films have been prepared by a hot-press casting procedure. Salt concentration dependent conductivity study at room temperature identified SPE film: [90PEO: 10 Zn(CF₃SO₃)₂] as optimum conducting composition (OCC) with σ _rt ~ 1.09 × 10⁻⁶ S/cm which is approximately three orders of magnitude higher than that of pure PEO host (σ _rt ~ 3.20 × 10⁻⁹ S/cm). The reason attributed for σ _rt enhancement has been the increase in degree of amorphous phase in polymeric host after salt complexation. This has been confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. To evaluate the usefulness of SPE OCC film in all-solid-state-battery applications, ion transport property has been characterized in terms of basic ionic parameters viz. ionic conductivity (σ) and total ionic (t _ion)/cation (t ₊) transport numbers. Mechanism of ion transport has been explained by temperature dependent conductivity measurements and the activation energy (E _a) has been computed by least square linear fitting of “log σ − 1/T” Arrhenius plot.

     

Multi-component, 1,3-dipolar cycloaddition reactions for the chemo-, regio- and stereoselective synthesis of novel hybrid spiroheterocycles in ionic liquid

A library of novel 1-methyl-4-arylpyrrolo-(spiro[2.2′]indan-1′,3′-dione)-spiro[3.3″]-1″-methyl/benzyl-5″-(arylmethylidene)piperidin-4″-ones and 1-methyl-4-arylpyrrolo-(spiro[2.11′]-11H-indeno[1,2-b]quinoxaline)-spiro[3.3″]-1″-methyl/benzyl-5″-(arylmethylidene)piperidin-4″-ones have been synthesized via 1,3-dipolar azomethine ylide cycloaddition in the ionic liquid, 1-butyl-3-methylimidazolium bromide ([BMIm]Br), in excellent yields.     

Stable physically adsorbed coating of poly-vinyl alcohol for the separation of basic proteins

In aqueous capillary electrophoresis, the electroosmotic flow can be strongly suppressed by coating the inner surface of the capillary. In the present work hydrophilic coating of 4% polyvinyl alcohol (PVA) has been used for the analysis of basic proteins. The coating is simple and easy to obtain. The separation of ribonuclease and α-chymotrypsin has been uniquely done with other three basic proteins (lysozyme, cytochrome-c and trypsin) using a buffer 11.60 mM sodium acetate and 18.40 mM acetic acid at pH 4.5 in addition to positive power supply of 20 kV at 25°C. Detection was performed using UV detector at 230 nm. The proposed PVA coated capillary provides reproducible separation of five basic proteins within 10 min with RSD values for mobility bellow 1.4% (n = 6) for all the five basic proteins. The stability of coated capillary has been checked up to 40 runs. The viscosity measurement for 4% PVA have been studied and scanning electron microscope (SEM) images obtained to make it compatible with future micro-chip applications.     

A rational design of the multiwalled carbon nanotube–7,7,8,8-tetracyanoquinodimethan sensor for sensitive detection of acetylcholinesterase inhibitors

A new, simple and effective amperometric acetylcholinesterase biosensor was developed using screen-printed carbon electrodes modified with carbon nanotubes (MWCNTs)–7,7,8,8-tetracyanoquinodimethane (TCNQ). The design of the biosensor was based on the supramolecular arrangement resulted from the interaction of MWCNTs and TCNQ. This arrangement was confirmed by spectroscopic and electrochemical techniques. Two different supramolecular arrangements were proposed based on different MWCNTs:TCNQ ratios. The synergistic effect of MWCNTs and TCNQ was, for the first time, exploited for detection of thiocholine at low potential with high sensitivity. The biosensor developed by immobilization of acetylcholinesterase (AChE) in sol–gel allowed the detection of two reference AChE inhibitors, paraoxon-methyl and chlorpyrifos with detection limits of 30 pM (7 ppt) and 0.4 nM (0.1 ppb), respectively. Efficient enzyme reactivation was obtained by using obidoxime.     

Hydrogen bonded co-crystallised layered isopropanol-pyrogallol[4]arenes

A novel isopropanol-pyrogallol[4]arene forms a layered structure via hydrogen bonding and C–H…π interactions. The layered structure results in encapsulation of one isopropanol molecule. The application of NMR methods to determine solution structures and crystal structures provides insight into host–guest properties and the molecular interactions between them.     

Electronic and magnetic properties of basic nanosystems of early 3d transition metals (Sc,Ti, V,Cr, and Mn)

This detailed and systematic theoretical study on the behavior of basic low dimensional (one- and two-dimensional) systems of early 3d transition metals should serve as a guideline to experimentalists as well as to theoreticians. We find that, lowering of dimensionality is favorable for emergence of magnetic ordering in all the systems studied, except Ti monolayers (MLs). For Ti MLs, both nonmagnetic and ferromagnetic states are degenerate within the numerical limits. For such a case, the interactions with substrate would play a decisive role in the magnetic ordering of the atoms in the ML. The total energy calculations show that the nonmagnetic and ferromagnetic states are almost degenerate for Cr and V MLs too; however, anti-ferromagnetic ordering is favored in these. The ferromagnetic ordering in Sc linear chains and anti-ferromagnetic ordering in MLs of Mn and Cr are found to be favored by a relatively larger margin showing good stability. Some low dimensional systems, showing electrons with only one kind of spin available at Fermi energy, may be suitable for spintronics related applications. The linear chains of Cr and Mn, and MLs of Sc are likely to form stable magnetic nanosystems as these exhibit almost saturated magnetic moment per atom around the equilibrium separation. The magnetic moment strengthens considerably as one goes from two- to one-dimension. Our results are supported qualitatively by available experimental results and offer a good insight into these nanosystems.     

Gas-expanded liquids for sustainable catalysis and novel materials: Recent advances

Employing a multiscale systems-based research approach, chemists and chemical engineers at the Center for Environmentally Beneficial Catalysis (CEBC) are collaboratively addressing major grand challenges facing the sustainable manufacture of fuels and chemicals from both traditional and renewable feedstocks. By judiciously combining the principles of green chemistry and green reactor engineering, augmented by valuable insights from industrial partners, CEBC researchers are developing alternative technology concepts that minimize the environmental footprint of chemical manufacturing processes including the reduction of carbon emissions. Such collaborations have resulted in several remarkable discoveries as follows: CO₂-expanded liquids (CXLs) as reaction media for selective and inherently safe O₂ oxidations including that for terephthalic acid production from p-xylene with potentially reduced solvent burning (i.e., reduced carbon footprint); propylene oxide production with environmentally benign solvents and oxidant, exploiting the compressibility of propylene at ambient temperatures for process intensification; a novel pressure-intensified ethylene oxide process virtually eliminating CO₂ formation as a byproduct; highly selective hydroformylation of higher olefins employing CXLs and soluble polymer-supported homogeneous Rh-based catalysts that are easily retained in solution while the product is isolated by membrane filtration; and creation of nanoparticles of transition metal complexes with unique functional properties such as reversible oxygen binding and room-temperature nitric oxide disproportionation. Quantitative economic and environmental impact analyses have been employed to benchmark CEBC's novel technology concepts against conventional processes and to guide research and development. Examples of such advances in green processing are discussed in this review.     

Ternary semigroups

A ternary semigroup is a nonempty set together with a ternary multiplication which is associative. Analogous to the theory of semigroups, a regularity condition on a ternary semigroup is introduced and the properties of regular ternary semigroups are studied. Associated with a ternary semigroup, a semigroup called the semigroup cover is constructed and its properties are investigated.