新法制备铁氰化钴修饰玻碳电极及多巴胺的电催化氧化

新法制备铁氰化钴修饰玻碳电极及多巴胺的电催化氧化     

Mixed ionic-electronic conductivity in phases in the praseodymium oxide system

The praseodymium oxide system contains a series of related phases with very narrow compositional width and unique extended defect structures, rather than the more common isolated point defects. The electrical conductivity of three of these phases has been measured by the use of AC complex impedance and DC methods in the temperature range 75–400 °C. The beta phase, Pr₆O₁₁, exhibits a total conductivity of 6.77×10^–2 S/cm at 400 °C, with an activation energy of 0.52 eV/atom. The conductivity of the epsilon phase, Pr₅O₉, is slightly lower, with an activation energy of 0.51 eV/atom. The iota phase, Pr₇O₁₂, has a very low conductivity. The activation energies for electrical transport in the beta and epsilon phases are in the general range found in a number of mixed conductors based upon LSGM oxides. Electronic Publication     

A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

The oxidation of methyl ester of pectic acid (pectin) (PEC) by a hexacyanoferrate(III) ion at a constant ionic strength of 0.1 mol dm⁻³ has been investigated spectrophotometrically. The oxidation rates were found to increase with increasing the alkali concentration, indicating that the nature of reaction was base catalyzed. The agreement of [pectin] dependence of the rate constants to the Michaelis-Menten kinetics proves the formation of 1:1 intermediate complex prior to the rate-determining step. The deviation of the pseudo–first-order curves from linearity after 65-70% of reaction completion indicates the interference of some oxidation products during the reaction progression. The oxidation process was proceeding via a free-radical intervention mechanism. The activation parameters have been evaluated, and a suitable reaction mechanism is suggested and discussed.     

Effects of Praseodymium Doping on Conductivity and Oxygen Permeability of Cobalt-Free Perovskite-Type Oxide BaFeO3-δ

Among the perovskite-type oxides with symmetrical structure applied in oxygen permeable membranes, cubic phase structure is the most favorable for oxygen permeation.In order to stabilize the cubic perovskite structure of BaFeO_3-δ material at room temperature, iron was partially substituted by praseodymium.BaFe_1-yPr_yO_3-δ powders were synthesized by a solid state reaction method, and sintered samples were prepared from the synthesized BaFe_1-yPr_yO_3-δ powders.X-ray diffraction results reveal that the BaFe_1-yPr_yO_3-δ samples remain cubic structure at praseodymium substitution amount of y=0.05, 0.075, 0.1.Scanning electron microscope observation indicates that the sintered samples contain only a small amount of enclosed pores and the grain size of BaFe_1-yPr_yO_3-δ increase monotonically with the increase of the praseodymium doping amount, praseodymium doping promotes the grain size growth.Tests of electrical conductivity and oxygen permeation flux show that praseodymium doping improves the conduction properties of BaFe_1-yPr_yO_3-δ and BaFe_0.9Pr_0.1O_3-δ composition has an electrical conductivity of 6.5 S/cm and an oxygen permeation of 1.112 mL/(cm²·min) at 900 ℃, respectively.High temperature XRD investigation shows that the crystal structure of BaFe_0.975Pr_0.025O_3-δ membrane completely transform to cubic phase at 700 ℃.The present test results have shown that partially substitution of Fe by praseodymium in BaFeO₃ can stabilize the cubic structure and improve the properties.     

Ferricyanide Confined in a Protonated Amine-Functionalized Silica Film on Gold: Application to Electrocatalytic Sensing of Nitrite Ions

An amine-functionalized porous sol–gel silica film was shown to be an effective platform to immobilize small anionic redox mediators of high solubility on solid electrodes by electrostatic interaction. The highly soluble mediator hexacyanoferrate was used as a model. The film was grown and firmly anchored on a gold electrode surface via thiol groups of a self-assembled monolayer of (3-mercaptopropyl)trimethoxysilane. Film growth and thickness were controlled by electrochemical modulation of pH at the electrode/solution interface in a sol of a hydrolyzed solution of tetraethoxysilane and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane by the application of a negative potential to the electrode. Protonation of the amine groups made the amine-functionalized surface useful to immobilize hexacyanoferrate on gold. Thus, the immobilization is pH dependent, being highly effective in strongly acidic medium. Cyclic voltammetry and scanning electron microscopy were used to characterize the film and to optimize the experimental conditions. The stability of the film was demonstrated by applying the catalytic properties of the hexacyanoferrate containing surface for nitrite sensing using a flow injection analysis (FIA) system. Under the optimized conditions, the sensor exhibited high sensitivity, low detection limit, easy handling, and stability with a linear range from 1.0 to 40.0?µmol?L^?1 and a detection limit of 0.53?µmol?L^?1 based on a signal-to-noise ratio of 3. The sensor was successfully applied to nitrite determination in water samples using FIA with excellent recoveries.     

Cs4[Sc6C]Cl13 und Cs4[Pr6(C2)]I13 — zwei Beispiele für das fehlende Bindeglied bei der Verknüpfung der Baueinheiten [M6Z]XX

Cs₄[Sc₆C]Cl₁₃ and Cs₄[Pr₆(C₂)]I₁₃ — Two Examples for the Missing Link in the Connectivity of [M₆Z]X X Building Units Cs₄[Sc₆C]Cl₁₃ (tetragonal, I4₁/amd, a = 1 540.5(4), c = 1 017.9(7) pm, c/a = 0.661, Z = 4, R = 0.038, R_w = 0.026) and Cs₄[Pr₆(C₂)]I₁₃ (a = 1 804.9(3), c = 1 259.5(3) pm, c/a = 0.698, R = 0.106, R_w = 0.068) are obtained as green-black and blue-black single crystals with brass-like metallic lustre through metallothermic reduction of ScCl₃ and PrI₃, respectively, with cesium in the presence of carbon in sealed tantalum containers. The, overall, isotypic compounds contain isolated [Sc₆C] and [Pr₆(C₂)] clusters, respectively, that are surrounded by 18 halide (X) ligands (12 Xⁱ and 6 X^a; X = Cl or I). The connection is carried out via the motif [M₆Z]XXXX (M = Sc and Pr; Z = C and C₂, respectively) and is thereby the missing link of the motifs of connection for the composition A_x[M₆Z]X₁₃. Analogous interconnection of [TiO₆] octahedra is found in the anatase-type of structure of TiO₂.     

Assembly process of CuHCF/MPA multilayers on gold nanoparticles modified electrode and characterization by electrochemical SPR

Gold nanoparticles were deposited onto 2-mercaptoethylamine (MEA)-assembled planar gold thin film to construct gold nanoparticles modified electrode by virtue of a solution-based self-assembly strategy. Subsequently, 3-mercaptopropionic acid (MPA)-bridged copper hexacyanoferrate (CuHCF) multilayers were constructed on the as-prepared gold nanoparticles modified electrode. The resulted multilayer nanostructures were investigated by electrochemical surface plasmon resonance (EC-SPR) and atomic force microscopy (AFM) with primary emphasis upon the effect of the gold nanoparticles on the MPA/CuHCF multilayers growth and their surface morphology. Compared with the multilayer system on a planar gold electrode, the different electrochemical and optical properties might result from higher curvature effect and extraordinary surface-to-volume ratio characteristic of gold nanoparticles and the nanoparticle-selective growth of CuHCF. A dendrimer-like assembly process was proposed to explain the experiment results. This new motif of multilayer on the gold nanoparticles modified electrode was different from that of on a planar gold electrode, indicating a potential application of EC-SPR technique in the study of nanocomposite materials.     

Thermal decomposition of hydrotalcitewith hexacyanoferrate(II) and hexacyanoferrate(III) anions in the interlayer

The thermal decompositions of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer have been studied using thermogravimetry combined with mass spectrometry. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 11.1 and 10.9 Å which compares with a d-spacing of 7.9 and 7.98 Å for the hydrotalcite with carbonate or sulphate in the interlayer. XRD was also used to determine the products of the thermal decomposition. For the hydrotalcite decomposition the products were MgO, Fe₂O₃ and a spinel MgAl₂O₄. Dehydration and dehydroxylation take place in three steps each and the loss of cyanide ions in two steps.     

Die Kristallstruktur von KPr3Te8

Crystal Structure of KPr₃Te₈ Out of the compounds ALn₃Q₄ (A = Na, K, Rb, Cs; Ln = Lanthanoid; Q = S, Se and Te) the crystal structure of the telluride KPr₃Te₈ was determined by X‐ray single‐crystal structure analysis. Single crystals of the compound were synthesized by a flux technique with K₂Te₃ as flux after separation of the K₂Te₃ excess by extraction with absolute dimethylformamide (DMF). The compound crystallizes monoclinically in space group P12₁/c1 with the lattice parameters a = 1390.58(7) pm, b = 1291.06(6) pm, c = 900, 18(5) pm and β = 99, 264(6)° isotypically to KNd₃Te₈. Characteristics in the crystal structure of KPr₃Te₈ are L‐shaped units of three tellurium atoms [Te₃]^2— as well as infinite zig‐zag chains of tellurium atoms [Te₄]^4—. The shortest interatomic distances in the chain are alternating only slightly with 298 and 300 pm and are in the range of partial bonds. Both structure elements are arranged in almost planar layers and are interconnected with each other by secondary interactions revealing interatomic distances in the range of 327 to 349 pm. The crystal structure of KPr₃Te₈ can be regarded as a addition‐defect variant of the binary NdTe₃ structure type. This finding is illustrated by group‐subgroup relations in form of a so called Bärnighausen family tree.