Solid-state NMR study of N labelled polyaniline upon reaction with DPPH

The quantitative investigation of the radical scavenging properties of polyaniline (PANI) upon reaction with excess of the stable DPPH radical (a 4:1 ratio of DPPH to aniline units in the polymer) was carried out using ¹⁵N and ¹³C solid state NMR spectroscopy. During the process the polyaniline was oxidised so that the imine content increased from 45 to 65%. The extent of oxidation measured by NMR was confirmed by N1s XPS analysis. However, within a 30 min reaction time, about 85% of the DPPH radicals were scavenged as monitored by the decay in its EPR signal. This is about 20 times greater than the fraction of DPPH required to oxidize PANI from an imine content of 45-65%. An identification of further redox processes is required to explain the high degree of radical scavenging. At the same time, there was no evidence of significant chemical binding or trapping of DPPH in the PANI structure.     

Oxidative stability of structured lipids produced from borage (<Emphasis Type="Italic">Borago officinalis</Emphasis> L.) and evening primrose (<Emphasis Type="Italic">Oenothera biennis</Emphasis> L.) oils with docosahexaenoic acid

This study utilized γ-linolenic acid (18∶3n−6; GLA)-rich borage oil (BO) and evening primrose oil (EPO) for the synthesis of structured lipids (SL) and compared the oxidative stability of the products with those of unmodified BO and EPO as controls. Immobilized Novozym 435 lipase from Candida antarctica was used as the biocatalyst for SL production. BO or EPO eas enzymatically modified with docosahexaenoic acid (22∶6n−3; DHA), as the acyl donor, to produce SI. The SI were characterized and their oxidative stabilities evaluated. Among the oils examined, SL gave rise to higher quantities (P≤0.05) of conjugated dienes, TBARS, and headspace volatiles as compared to their unmodified counterparts. Results indicated that modified oils were less stable than their unmodified counterparts. The double bond index (DBI) and methylene bridge index (MBI) of oils decreased (P<0.05) during oxidation in the more unsaturated oils. An attempt was made to correlate various parameters of oxidation with DBI and MBI of oils; correlation coefficients (−r) were within the range of 0.574–0.973. This suggests that indicators such as DBI and MBI can reflect oxidative stability of oils.     

Kinematic Design and Analysis of a 7 Degree-of-Freedom Dual-Stage Inspection Manipulator for Dexterous Subsea Applications

This paper describes the design of a 7 degree-of-freedom (d.o.f) manipulator for underwater inspection applications. The functional requirements of an underwater manipulator for subsea inspection are discussed and the desired performance requirements identified. The inspection process of a weld joint using a manipulator is described and the desirable attributes of a 5 d.o.f manipulator for the inspection process established. A novel kinematic structure, for Underwater Robotic Vehicle (URV) operation, having a 2 d.o.f launching stages and a 5 d.o.f inspection stage is proposed for the manipulator. This configuration increases the dexterity, without compromising on the total reach of the manipulator. The kinematic structure of the 7 d.o.f, 2 stage, manipulator is presented. A hybrid power actuation is proposed for the manipulator to exploit the benefits of both hydraulic as well as electric actuators. Kinematic analysis of the manipulator is presented. The link dimensions of the inspection stage manipulator is done on the basis of kinematic performance indices of the manipulator. The novel kinematic structure and the hybrid power actuation strategy results in a power efficient, dexterous manipulator for underwater applications.     

A comparative study of the dependency of colour measurement on surface temperature

In this paper, we evaluated in depth how the spectrophotometric colour measurement of an object will respond to surface temperature change. The colorimetric variations of eight coloured ceramic tiles against temperature changes were studied. Colorimetric data measured at specific temperature were compared with data measured at about 20 °C. For each coloured ceramic tile, reflectance curves and colorimetric differences resulting from temperature differences were examined to demonstrate the exact dependency of colorimetric properties across the temperature range studied. Experimental data showed that peaks and slopes on a reflectance curve are the major impact resulting from temperature variation. Colours with lower lightness and lower chroma showed smaller colorimetric changes with change in temperature, while colour with higher lightness and chroma exhibited a distinct thermochromism and linearity changes across the temperature range. A conspicuous correlation potential between surface temperature and CIE colorimetric coordinates was observed.     

Unraveling the Dynamic Nanoscale Reducibility (Ce4+ → Ce3+) of CeOx–Ru in Hydrogen Activation

The interaction of molecular hydrogen with ceria is of important relevance for heterogeneous catalysis related to green chemistry and renewable energy. Here, the complex structural transformations of a well‐defined cerium oxide model catalyst are followed in situ and in real time when exposed to a reactive H₂ environment. By using electron spectromicroscopy and diffraction with chemical and structural sensitivities, it is demonstrated that the transition from CeO₂ to crystalline Ce₂O₃ occurs through a mixture of transient, coexisting phases on the nanoscale. The findings establish a clear relationship between structure and functionality for hydrogen dissociation over ceria(111), bearing profound implications on the nature of the reduction (Ce⁴⁺ → Ce³⁺) and mechanism for H₂ scission.     

Simple N‐Heterocyclic Carbenes as Ligands in Ullmann‐Type Ether and Thioether Formations

A simple N‐heterocyclic carbene (NHC) derived from 1‐methyl‐3‐ethylimidazolium tetrafluoroborate was found to be an efficient ligand for a range of copper‐catalyzed cross‐coupling reactions, leading to the formation of aromatic ethers and thioethers.

     

Acid leaching of metals from deep-sea manganese nodules – A critical review of fundamentals and applications

The mass% metal composition of deep sea nodules ranges from 10–28% Mn, 4–16% Fe, 0.3–1.6% Ni, 0.02–0.4% Co, and 0.1–1.8% Cu in mixed oxide matrices with alumina and silica. The concentrations of base metal ions in sea water of pH ∼ 8 of the order 10⁻³–10² nmol/kg are shown to be dependent on the solubility products (K_SP) of carbonate sediments. Cations of higher softness have higher pK_SP and lower solubility. Previously reported leach results of nodules in H₂SO₄ and HCl under atmospheric pressure and temperatures in the range 30–90 °C and in the absence or presence of SO₂, Na₂SO₃, NaCl and CaCl₂ are used in the present study to compare, contrast and rationalise the leaching behaviour of metal values. Leach efficiency of metals increases with increasing acid concentration, and Cu(II) and Zn(II) follow the same trend in HCl. Potential–pH diagrams of base metal oxides show a higher stability of mixed metal oxides such as ferrites, magnetite and manganite, which causes partial dissolution of high-valent oxides in the absence of reducing agents. Application of a shrinking core kinetic model in both H₂SO₄ and HCl media predicts a proton diffusivity of ∼ 10⁻¹¹ cm² s⁻¹ for the dissolution of Ni from nodules. This value is of the same order as D_H⁺ for the high pressure acid leaching of Ni from limonitic laterite. A linear correlation between leaching efficiencies of Fe and Ni appears to be a result of co-dissolution of these metals from NiO·Fe₂O₃ or NiFeOOH. The first order dependence of initial dissolution rates of Cu(II) with respect to H⁺ concentration in H₂SO₄, and the beneficial effect of background chloride ions, suggests a dissolution mechanism: CuO → Cu(OH)Cl_ads/aq → CuSO₄. The Cu(II) ions in solution can also affect Ni(II) dissolution from oxide by cation exchange mechanism. The presence of SO₂ or Na₂SO₃ as reducing agents facilitates the acid leaching of high-valent oxides of Mn and Co and other metals incorporated in the mixed oxide matrix. Whilst Fe(II) ions formed during the reductive leaching of Fe(III)-oxides accelerate the dissolution of Mn(III)/(IV) oxides, the resultant Mn(II) ions accelerate the dissolution of high-valent Co-oxides. Leaching efficiency in HCl increases with temperature. As for the SO₂/H₂O system thermodynamic calculations predict a decrease in concentration of H⁺ and at high temperatures, which retards leaching efficiency. The SO₂/H₂O/air leach system enhances metal dissolution due to the production of H₂SO₄ via the transition metal catalysed oxidation of SO₂ to H₂SO₄.     

Speciation and reduction potentials of metal ions in concentrated chloride and sulfate solutions relevant to processing base metal sulfides

The speciation, Eh-pH and Eh-log a_Cl- dependence of Fe(III), Fe(II), Cu(II), Cu(I), Ag(I), Pb(II), Zn(II), Ni(II), As(III), Sb(III), and Bi(III) ions in practical (high ionic strength) sulfate and chloride solutions are discussed. The emphasis is placed on those ions which form strong sulfato-, chloro-, and hydroxo-complex species. Measured potentials are compared with potentials calculated from reported association and stability constants to test the applicability of these constants in nonideal solutions and to characterize predominant species. Formerly Postgraduate Student, Murdoch University, Perth, Western Australia     

The Role of Electron Localization in Covalency and Electrochemical Properties of Lithium-Ion Battery Cathode Materials

Following the fundamental research conducted by J. B. Goodenough, the important role of electron localization induced by elemental substitution is studied. The size and electron negativity of host and substituting ions are two important factors in tuning material properties such as local structure and transition metal (TM) oxygen covalency. However, another factor, electron localization, which is widely studied in catalyst research but largely overlooked for battery materials, deserves systematic studies. A combined investigation using synchrotronbased X-ray spectroscopy and theoretical calculations is carried out on the Li-Co-Mn-O model system in which the substituting cation Mn⁴⁺, with its 3d³ electronic structure, is used as a promoter for electron localization. Results indicate that electron localization greatly influences the Co O bond by making it less covalent, which increases the delithiation voltage. It is also found that during charge/discharge, electron localization tends to make TM K-edge X-ray absorption near edge spectroscopy (XANES) spectra show a more “rigid shift” behavior while electron delocalization makes the XANES exhibit a “shape change.” It clearly explains why the K-edge XANES data of some TM oxides show no “rigid shift” while the nominal valence states changed. This work highlights the importance of electron localization with guidance for XANES interpretation.