Electrochemical properties of colloidal nanocrystal assemblies of manganese ferrite as the electrode materials for supercapacitors

The electrocapacitive behavior of MnFeO-based supercapacitors has been studied by a series of electrochemical techniques, including circle voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The size of the used MnFeO colloidal nanocrystal assemblies (CNAs) was in the range of 230–950\ua0nm, formed by the in situ self-assembly of primary MnFeO nanoparticles with different sizes. Electrochemical measurements showed that the electrochemical performances of MnFeO-based supercapacitors were related to the structure of MnFeO CNAs. MnFeO CNAs with the size of 420\ua0nm, composed of 16\ua0nm nanoparticles, displayed the highest capacitance of about 88.4\ua0F/g at the current density of 0.01\ua0A/g, which, respectively, decreased to 55.8 and 20.2\ua0F/g for CNAs with size of 230 and 950\ua0nm, assembled by 21 and 43\ua0nm nanoparticles. Electrochemical stability data showed that 420\ua0nm MnFeO CNAs had the best capacitance retention of 59.4% with the current density increased from 0.01 to 2\ua0A/g and the best capacitance retention of 69.2% after 2000 cycles among all the samples under the current density of 0.2\ua0A/g. The structure–property relationship of MnFeO CNAs was analyzed and discussed based on the experimental data

Electrospun γ-Fe2O3 nanofibers as bioelectrochemical sensors for simultaneous determination of small biomolecules

Nanofibers of alpha-Fe2O3 and gamma-Fe2O3 have been obtained after the controlled calcination of precursor nanofibers synthesized by electrospinning. alpha-Fe2O3 nanofibers showed an irregular toruloid structure due to the decomposition of poly (4-vinyl) pyridine in air while gamma-Fe2O3 nanoparticles decorated nanofibers were observed after the calcination under N-2 atmosphere. Electrochemical measurements showed that different electrochemical behaviors were observed on the glassy carbon electrodes modified by alpha-Fe2O3 and gamma-Fe2O3 nanofibers. The electrode modified by gamma-Fe2O3 nanofibers exhibited high electrocatalytic activities toward oxidation of dopamine, uric acid and ascorbic acid while alpha-Fe2O3 nanofibers cannot. Furthermore, the gamma-Fe2O3 modified electrode can realize the selective detection of biomolecules in ternary electrolyte solutions. The synthesis of nanofibers of alpha-Fe2O3 and gamma-Fe2O3 and their electrochemical sensing properties relationship have been discussed and analyzed based on the experimental results. (C) 2018 Elsevier B.V. All rights reserved

The electrocapacitive properties of polyaniline/VXC-72 composite electrodes

While polyaniline holds a great promise as an electrode material for pseudocapacitors, its poor stability against charge/discharge hinders its practical applications. In this work, polymerization of aniline was conducted in the presence of commercial carbon black VXC-72 to prepare polyaniline/VXC-72 composite electrodes. Results showed that the stability of the polyaniline/VXC-72 composite electrode was drastically improved with over 90% capacitance retention after 10,000 cycles at a current density of 2 A g(-1). It was found that VXC-72 particles played an important part in the chemical oxidative polymerisation process - they served not only as nucleation sites on which polymerization underwent to form polyaniline but also determined the morphology of the resultant solid product. The polyaniline/VXC-72 composite electrode materials with different contents of VXC-72 exhibited different morphologies and electrocapacitive performances. This research provides guidelines for designing polyaniline-carbon black composite electrode materials with an excellent stability against cycling, high capacitance, and low cost

Carrageenan Asissted Synthesis of Palladium Nanoflowers and Their Electrocatalytic Activity toward Ethanol

Palladium (Pd) nanoflowers with tunable thorns were prepared by a facile and rapid route with the assistance of carrageenan. The superior nature of well-dispersed Pd nanoflowers has been disclosed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy measurements. The growth of thorns of Pd nanostructures was first stimulated with the continuous introduction of l-ascorbic acid in the synthesis system and then reached a maximum length of about 132 nm, followed by a slight decrease in concentration. Electrochemical data showed that Pd nanoflowers with the longest thorns exhibited the highest catalytic current density of 1160 mA/mg, optimized tolerance to the poisoning, and the lowest onset potential while others showed a better cycle stability with a catalytic activity maintenance of above 96% after 300 cycles. It is suggested that the structure of thin thorns of Pd nanoflowers should be easier to damage than thick thorns during the electrocatalysis of ethanol. The relationship between Pd nanoflowers and properties as well as the key factors to form the nanoflower structure were discussed based on the experimental data

Frameworks for innovation, collaboration, and change: Value creation wheel, design thinking, creative problem‐solving, and lean

International audienceThe value creation wheel (VCW) is the decision-making meta-framework recommended to address innovation, collaboration, and change challenges in formal relationships. The VCW can integrate, complement, or be joined with other frameworks, tools, and theories to address the challenges of formal relationships. The VCW's ability to incorporate intra- and interorganizational insights emerging from internal and external stakeholders is especially useful in solving the challenges of collaborative arrangements. VCW solutions are often more realistic than Design Thinking, Creative Problem-Solving, and Lean because they accommodate the views of various stakeholders about ideas and filters, and because key decision makers must be involved in the main stages of the decision-making process

Solid phase extraction of uranium(VI) on phosphorus-containing polymer grafted 4-aminoantipyrine

Phosphorus-containing polymer grafted 4-aminoantipyrine has been synthesized and used for solid phase extraction of U(VI) prior to its UV-Visible spectrophotometric determination by using arsenazo(III). The adsorbent was characterized by using FT-IR and SEM analysis. The influence of parameters including pH, adsorbent dose, amount of complexing reagent, sample volume and matrix effect have been optimized. The detection limit was determined as 1.4 mu g L-1 with pre-concentration factor of 30 and RSD of 1.4 %. The accuracy was checked by the analysis of GBW07424 soil and TMDA-64.2 environmental water certified reference materials. The method was applied to natural water and soil samples