A rapid polyol combustion strategy towards scalable synthesis of nanostructured LiFePO4/C cathodes for Li-ion batteries

In the present study, carbon-coated lithium iron phosphate (LiFePO₄/C) is prepared directly by a polyol-assisted pyro-synthesis performed under reaction times of a few seconds in open-air conditions. The polyol solvent, tetraethylene glycol (TTEG), acts as a low-cost fuel to facilitate combustion and the released exothermic energy promotes the nucleation and growth processes of the olivine nanoparticles. In addition, phosphoric acid (used as the phosphorous source) acts as a catalyst to accelerate polyol carbonization. The structure analysis of the as-prepared LiFePO₄/C using X-ray, neutron diffraction and ⁷Li NMR studies suggested the efficacy of the rapid technique to produce highly crystalline phase-pure olivine nanocrystals. The electron microscopy and particle-size distribution studies revealed that the average particle diameters lie below 100 nm and confirmed the presence of a surface carbon layer of 2–3 nm thickness. The thermal and elemental studies indicated that the carbon content in the sample was approximately 5 %. The prepared LiFePO₄/C cathode delivered capacities of 162 mA h g^-1 at 0.1 °C rates with impressive capacity retention for extended cycling. The polyol-assisted pyro-synthesis, which evades the use of external energy sources, is not only a straightforward, simple and timely approach but also offers opportunities for large-scale LiFePO₄/C production.     

Enzymatic Desymmetrising Redox Reactions for the Asymmetric Synthesis of Biaryl Atropisomers

Atropisomeric biaryls carrying ortho‐hydroxymethyl and formyl groups were made enantioselectively by desymmetrisation of dialdehyde or diol substrates. The oxidation of the symmetrical diol substrates was achieved using a variant of galactose oxidase (GOase), and the reduction of the dialdehydes using a panel of ketoreductases. Either M or P enantiomers of the products could be formed, with absolute configurations assigned by time‐dependent DFT calculations of circular dichroism spectra. The differing selectivities observed with different biaryl structures offer an insight into the detailed structure of the active site of the GOase enzyme.     

Multifunctional Supramolecular Dendrimers with an s‐Triazine Ring as the Central Core: Liquid Crystalline,Fluorescence and Photoconductive Properties

Novel liquid crystal (LC) dendrimers have been synthesised by hydrogen bonding between an s‐triazine as the central core and three peripheral dendrons derived from bis(hydroxymethyl)propionic acid. Symmetric acid dendrons bearing achiral promesogenic units have been synthesised to obtain 3:1 complexes with triazine that exhibit LC properties. Asymmetric dendrons that combine the achiral promesogenic unit and an active moiety derived from coumarin or pyrene structures have been synthesised in order to obtain dendrimers with photophysical and electrochemical properties. The formation of the complexes was confirmed by IR and NMR spectroscopy data. The liquid crystalline properties were investigated by differential scanning calorimetry, polarising optical microscopy and X‐ray diffractometry. All complexes displayed mesogenic properties, which were smectic in the case of symmetric dendrons and their complexes and nematic in the case of asymmetric dendrons and their dendrimers. A supramolecular model for the lamellar mesophase, based mainly on X‐ray diffraction studies, is proposed. The electrochemical behaviour of dendritic complexes was investigated by cyclic voltammetry. The UV/Vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers were also investigated     

Electromechanical phase transition in hexacyanometallate nanostructure (Prussian Blue)

This paper demonstrates the importance of the structural changeover in controlling the physical-chemical properties of hexacyanometalate-like materials (Prussian Blue). A meticulous in situ study of compositional variations using electroacoustic impedance techniques associated to electrogravimetric techniques in hexacyanoferrates containing K+ alkali metals reveals the existence of a nanostructural changeover coupled to a change of the magnetic properties of these electromagnetic materials. In the same way, the electroacoustic impedance techniques can be useful both in the understanding and in the in situ monitoring of the structural changeovers and the magnetic behavior of all kinds of materials.     

Magnetism in polyoxometalates: anisotropic exchange interactions in the Co3II moiety of [Co3W(D2O)2(ZnW9O34)2](12-)--A magnetic and inelastic neutron scattering study

The ground-state properties of a Co3II moiety encapsulated in a polyoxometalate anion were investigated by combining measurements of specific heat, magnetic susceptibility, and low-temperature magnetization with a detailed inelastic neutron scattering (INS) study on a fully deuterated polycrystalline sample of Na12[Co3W(D2O)2(ZnW9O34)2].40D2O (Co3). The ferromagnetic Co3O14 cluster core consists of three octahedrally oxo-coordinated CoII ions. According to the single-ion anisotropy and spin-orbit coupling of the octahedral CoII ions, the appropriate exchange Hamiltonian to describe the ground-state properties of the Co3 spin cluster is anisotropic and is expressed as H = -2 sigma a = x,y,z (Ja12 S1a S2a + Ja23 S2a S3a), where Ja are the components of the exchange interactions between the CoII ions. To reproduce the INS data, different orientations of the two anisotropic J tensors must be considered, and the following conditions had to be introduced: Jx12 = Jy23, Jy12 = Jx23, Jz12 = Jz23. This result was correlated with the molecular symmetry of the complex. The following set of parameters was obtained: Jx12 = Jy23 = 1.37, Jy12 = Jx23 = 0.218, and Jz12 = Jz23 = 1.24 meV. This set also reproduces in a satisfactory manner the specific heat, susceptibility, and magnetization properties of Co3.     

Graphical analysis of electrochemical impedance spectroscopy of two consecutive irreversible electron transfers. 2. Zinc anodic dissolution in acid media

The graphical analysis of the impedance plots is used in the study of the electrodic systems that take place through two consecutive single electron transfers. The zinc anodic dissolution is studied by using this procedure. The characteristic points easily allow us to explain and to simulate the impedance behavior of this electrodic system according to the steady-state potential and the roughness of the working electrode. The direct procedure for parametrical identification from the graphical analysis allows us to reduce the time needed for an impedance experiment. This graphical analysis is suggested for studying thin coated galvanized steels.     

Adsorption of polyallylamine to lignocellulosic fibres: effect of adsorption conditions on localisation of adsorbed polyelectrolyte and mechanical properties of resulting paper sheets

Cationic polyallylamine (PAH), was adsorbed onto lignocellulosic fibres, and a fluorescent label on the polyelectrolyte enabled its location to be shown by confocal fluorescence microscopy. The adsorption time and ionic strength were varied to study their effect on the localisation of the adsorbed PAH. The microscopy showed that a long adsorption time, 24 h, and a high ionic strength, 10⁻¹ M NaCl + 5 × 10⁻³ M NaHCO₃ or higher, resulted in the adsorption of polyallylamine throughout the fibre walls. Shorter adsorption times and/or lower ionic strength resulted in adsorption only to the fibre exterior. By preparing sheets from fibres with polyelectrolyte adsorbed either to the exterior parts or into the fibre cell wall and testing their mechanical behaviour, a link was established between the localisation of adsorbed polyelectrolyte and the mechanical properties. Adsorption to the fibre exterior led to an increase in tensile strength and strain at break. The creep deformation at 90%RH was also slightly reduced by the adsorption of low molecular weight PAH (15 kDa). When polyallylamine was adsorbed throughout the wall of the lignocellulosic fibres, the mechanical properties were not however improved and the creep deformation at 90%RH actually increased somewhat.