Cobalt–iron decorated tellurium nanotubes for high energy density supercapacitor

We report the synthesis of cobalt-iron (Co–Fe) decorated tellurium nanotubes (Te NTs) using semiconductive Te NTs as a sacrificial template, following a wet chemical method. The interplay of Co and Fe precursor concentrations incorporated with Te NT, residual hydrazine hydrate, and the negative surface charge of Te NT plays a significant role in obtaining various bimetallic telluride structures. The one-dimensional (1-D) structure of Co–Fe decorated Te NTs with Te NTs in the backbone provides superior conductivity and exhibits high electrochemical performance with battery type electrode behavior. A negative surface charge value of ?18.9 mV for Te NTs is obtained due to the presence of an anionic surfactant as sodium dodecyl sulfate (SDS) forms a bilayer on Te NTs. To tune the energy density performance, the Co–Fe decorated Te NTs electrode is combined with the electric double-layer capacitors (EDLC) type electrode activated carbon (AC). The asymmetric assembly shows an excellent specific capacitance of 179.2 F/g (48.7 mAh/g) at a current density of 0.9 A/g in 4 M KOH electrolyte. More importantly, it exhibits a maximum energy density of 62.1 Wh/kg at a power density of 1,138.2 W/kg under a potential window of 1.58 V. This potential finding shows the significant applicability of Te NTs as a template for the synthesis of bimetallic tellurides with unique morphologies. The synergistic effect from multiple metals and anisotropic morphology is beneficial for energy storage applications.     

Thermal behavior of flax and jute reinforced in matrix acrylic composite

Natural fabric such as flax and jute was considered in biaxial plain reinforcement in matrix of acrylic resin, and the composite is prepared in hand layup techniques. Fabric mass fraction of 7% was used in the matrix of composite. The samples were treated at r.t and 60 °C for the final fabrication. Scanning electron microscopy was carried out to support the microstructure effect of composite in terms of thermal change. Thermogravimetric and differential thermogravimetric analysis and residual compositional analysis with FTIR were carried out for the composite and matrix samples. The mechanical and viscoelastic properties, as well as the influence of frequency and fibers types, were evaluated, in flexural mode, by means of dynamical mechanical analysis. Glass transition (T _g) and initial decomposition (T _i) temperatures increase with incorporation of fibers into the matrix. While T _i of flax and jute composite was similar, T _g in case of flax improves than jute fabric-reinforced composite. This type of composites can be used in the automotive sector, in exterior and exterior components.     

POLYPHASIC CHLOROPHYLL a FLUORESCENCE TRANSIENT IN PLANTS AND CYANOBACTERIA*

Abstract— The variable chlorophyll (Chl) a fluorescence yield is known to be related to the photochemical activity of photosystem II (PSII) of oxygen-evolving organisms. The kinetics of the fluorescence rise from the minimum yield, F₀, to the maximum yield, F_m, is a monitor of the accumulation of net reduced primary bound plastoquinone (Q_A) with time in all the PSII centers. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK), which allows data accumulation over several orders of magnitude of time (40 μs to 120 s), we have measured on a logarithmic time scale, for the first time, the complete polyphasic fluorescence rise for a variety of oxygenic plants and cyanobacteria at different light intensities. With increasing light intensity, the fluorescence rise is changed from a typical O-I-P characteristic to curves with two intermediate levels J and I, both of which show saturation at high light intensity but different intensity dependence. Under physiological conditions, Chl a fluorescence transients of all the organisms examined follow the sequence of O-J-I-P. The characteristics of the kinetics with respect to light intensity and temperature suggest that the O-J phase is the photochemical phase, leading to the reduction of Q_A to Q_A^-. The intermediate level I is suggested to be related to a heterogeneity in the filling up of the plastoquinone pool. The P is reached when all the plastoquinone (PQ) molecules are reduced to PQH₂. The addition of 3-(3–4-dichlorophenyl)-1,1-dimethylurea leads to a transformation of the O-J-I-P rise into an O-J rise. The kinetics of O-J-I-P observed here was found to be similar to that of O-I₁-I₂-P, reported by Neubauer and Schreiber (Z. Naturforsch. 42c , 1246–1254, 1987). The biochemical significance of the fluorescence steps O-J-I-P with respect to the filling up of the plastoquinone pool by PSII reactions is discussed.     

Polymerization of acrylonitrile. Kinetics of the reaction initiated by the vanadium(V)/thioglycollic acid redox system

The polymerization of acrylonitrile initiated by the vanadium(V)-thioglycollic acid redox system has been investigated in aqueous sulphuric acid under nitrogen over the range 30–45°. The polymerization is second order in monomer and first order in thioglycollic acid (TGA). The rate of vanadium(V) disappearance is proportional to (TGA) and [V(V)]. The effects of FeCl₃, CuSO₄ and acetic acid on the polymerization have been investigated. The proposed reaction scheme involves initiation by an organic free radical, produced by the interaction of V(V) with TGA and termination by V(V). Various rate parameters have been evaluated.     

Substituent effects in the reaction between benzaldehydes and polyacrylonitrile radicals

The effects of substituents on the reaction of benzaldehydes with polyacrylonitrile radicals have been studied in terms of the multiparameter equations based on Swain and Lupton's Field and Resonance (F and R) components with the unique positional weighting factors f and r developed by Williams and Norrington. From the nature of the reaction constants, a polar transition state has been postulated.     

Polymerization of acrylonitrile initiated by thiourea–chromium(VI) redox system

The kinetics of polymerization of acrylonitrile initiated by Cr(VI)–thiourea and Cr(VI)–ethylene thiourea have been studied at 35, 40, and 45°C in nitrogen. The rates of polymerization and of disappearance of Cr(VI) were measured. Chromic acid alone did not initiate the polymerization under deaerated and undeaerated conditions. On the basis of the experimental observation of the dependence of the rate of polymerization R_p, the rate of Cr(VI) disappearance, –R_m, etc., on various variables, a suitable kinetic scheme was proposed and various rate and energy parameters were evaluated.     

Reduced Graphene Oxide–Ag3PO4 Heterostructure: A Direct Z‐Scheme Photocatalyst for Augmented Photoreactivity and Stability

A visible light driven, direct Z‐scheme reduced graphene oxide–Ag₃PO₄ (RGO–Ag₃PO₄) heterostructure was synthesized by means of a simple one‐pot photoreduction route by varying the amount of RGO under visible light illumination. The reduction of graphene oxide (GO) and growth of Ag₃PO₄ took place simultaneously. The effect of the amount of RGO on the textural properties and photocatalytic activity of the heterostructure was investigated under visible light illumination. Furthermore, total organic carbon (TOC) analysis confirmed 97.1 % mineralization of organic dyes over RGO–Ag₃PO₄ in just five minutes under visible‐light illumination. The use of different quenchers in the photomineralization suggested the presence of hydroxyl radicals ( ^. OH), superoxide radicals ( ^. O₂^?), and holes (h⁺), which play a significant role in the mineralization of organic dyes. In addition to that, clean hydrogen fuel generation was also observed with excellent reusability. The 4 RGO–Ag₃PO₄ heterostructure has a high H₂ evolution rate of 3690 μmol h^?1 g^?1, which is 6.15 times higher than that of RGO.     

Field induced spin reorientation transition in epitaxial La0.5Sr0.5CoO3 films

Strained epitaxial La_0.5Sr_0.5CoO₃ films are grown on LaAlO₃ substrate. Structural, electrical, and magnetic measurements were carried out. Out of plane lattice parameter of the film undergoes compressive strain and the coercivity is enhanced. The zero field cooled (ZFC) magnetization curve for a field applied parallel to the film plane shows a jump, which suggests a spin reorientation transition (SRT), while ZFC magnetization for a field applied perpendicular to the film plane is featureless. This jump in magnetization is shifted to higher temperatures when the magnetic field is reduced. The SRT is attributed to the strain in the film.     

Reaction of water soluble polymers with oxidising agents: reaction of dextran with tetravalent cerium

Dextran, an extracellular bacterial polysaccharide, was subjected to reaction with ceric ammonium nitrate in aqueous nitric acid at varying temperatures. The polymer has been found to be degraded due to the selective oxidative cleavage of vicinal glycol units present in the monosaccharide unit of each chain. The aldehyde groups produced upon cleavage at low temperature were found to undergo further oxidation to acids and formic acid with rise in temperature of the reaction. The course of the reaction has been followed by cerimetry and by spectrophotometrical measurements. The effect of the concentration of reacting components on the reaction has been studied and various kinetic aspects have been evaluated. Depending on the kinetic results, a plausible reaction mechanism for the oxidative degradation and the subsequent reactions have been suggested by the study of the changes of solution viscosity and initiation of graft copolymerization of vinyl monomers by Ce(IV)/dextran mixture. Various thermodynamic parameters have been evaluated.