Arynic Condensation of Nitrile Anions in the Presence of the Complex Base NaNH2-CH3CH2(OCH2CH2)2ONa

Nitrite anions are easily condensed with aryl halides in the presence of the Complex Base NaNH₂-CH₃CH₂(OCH₂CH₂)₂ONa via the intermediate arynes.     

Coordination polymer chains built from CuII and adipate ions linked by hydrogen bonds to form a three‐dimensional framework structure

In the title compound, catena‐poly[bis[(2,2′‐bipyridine‐κ²N,N′)(1,1,3,3‐tetracyano‐2‐ethoxypropenido‐κN)copper(II)]‐μ₄‐hexanedioato‐κ⁶O¹,O^1′:O¹:O⁶,O^6′:O⁶], [Cu₂(C₉H₅N₄O)₂(C₆H₈O₄)(C₁₀H₈N₂)₂]_n, the adipate (hexanedioate) dianion lies across a centre of inversion in the space group P. The Cu^II centre adopts a distorted form of axially elongated (4+2) coordination, and the Cu^II and adipate components form a one‐dimensional coordination polymer from which the 2,2′‐bipyridine and 1,1,3,3‐tetracyano‐2‐ethoxypropenide components are pendent, and where each adipate dianion is bonded to four different Cu^II centres. The coordination polymer chains are linked into a three‐dimensional framework structure by a combination of C—H...N and C—H...O hydrogen bonds, augmented by a π–π stacking interaction.     

Mathematical Model and Numerical Simulation of Conductometric Biosensor of Urea

In this article, a mathematical model was developed to describe and optimize the configuration of the urea biosensor. The biosensor is based on interdigitated gold microelectrodes modified with a urease enzyme membrane. The model presented here focuses on the enzymatic reaction and/or diffusion phenomena that occur in the enzyme membrane and in the diffusion layer. Numerical resolution of differential equations was performed using the finite difference technique. The mathematical model was validated using experimental biosensor data. The responses of the biosensor to various conditions were simulated to guide experiments, improve analytical performance, and reduce development costs.     

A Highly Sensitive and Selective Non-enzymatic Hydrogen Peroxide Sensor Based on Nanostructured Co3O4 Thin Films Using the Sol-gel Method

In this work we report an easy and efficient way to fabricate nanostructured cobalt oxide (Co₃O₄) thin films as a non-enzymatic sensor for H₂O₂ detection. Co₃O₄ thin films were grown on ITO glass substrates via the sol-gel method and characterized with several techniques including X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorbance. The Co₃O₄ thin films’ performance regarding hydrogen peroxide detection was studied in a 0.1 M NaOH solution using two techniques, cyclic voltammetry (CV) and amperometry. The films exhibited a high sensitivity of 1450 μA.mM⁻¹.cm⁻², a wide linear range from 0.05 μM to 1.1 mM, and a very low detection limit of 18 nM. Likewise, the Co₃O₄ thin films produced showed an exceptional stability and a high selectivity.     

Mathematical Modelling of Glyphosate Molecularly Imprinted Polymer-Based Microsensor with Multiple Phenomena

The massive and careless use of glyphosate (GLY) in agricultural production raises many questions regarding environmental pollution and health risks, it is then important to develop simple methods to detect it. Electrochemical impedance spectroscopy (EIS) is an effective analytical tool for characterizing properties at the electrode/electrolyte interface. It is useful as an analytical procedure, but it can also help in the interpretation of the involved fundamental electrochemical and electronic processes. In this study, the impedance data obtained experimentally for a microsensor based on molecularly imprinted chitosan graft on 4-aminophenylacetic acid for the detection of glyphosate was analyzed using an exact mathematical model based on physical theories. The procedure for modeling experimental responses is well explained. The analysis of the observed impedance response leads to estimations of the microscopic parameters linked to the faradic and capacitive current. The interaction of glyphosate molecules with the imprinted sites of the CS-MIPs film is observed in the high frequency range. The relative variation of the charge transfer resistance is proportional to the log of the concentration of glyphosate. The capacitance decreases as the concentration of glyphosate increases, which is explained by the discharging of the charged imprinted sites when the glyphosate molecule interacts with the imprinted sites through electrostatic interactions. The phenomenon of adsorption of the ions in the CMA film is observed in the low frequency range, this phenomenon being balanced by the electrostatic interaction of glyphosate with the imprinted sites in the CS-MIPs film.     

The study on the ZnO and Zn0.95Mn0.05O added YBCO system: Investigation of microstructure and transport properties

The effect of nano-size Zn_0.95Mn_0.05O and ZnO (30 nm) addition on the microstructure and the normal state transport properties of polycrystalline YBa₂Cu₃O_y (YBCO) was systematically studied. Samples were synthesized in air using a standard solid state reaction technique by adding nano-sized particles up to 10 wt.%. When Zn_0.95Mn_0.05O and ZnO are added to the YBCO the orthorhombic structure maintained even at the highest concentration. TEM and EDS analyses show the presence of inhomeginities embedded in the superconducting matrix. To interpret the normal state properties of the samples, the percolation theory based on localized states is applied. A cross-over between variable-range hopping and Coulomb gap mechanisms is observed as a result of increasing the nano-particles concentration. The ZnO addition modifies the electrical behavior of samples from metallic to insulating with a much lower concentration comparatively to Zn_0.95Mn_0.05O addition. The calculated values of the localization length, d, are greater in the case of Zn_0.95Mn_0.05O addition. This result can be interpreted by the internal structure defects.     

High-dimensional mixed-valence copper cyanide complexes: Syntheses,structural characterizations and magnetism

Reactions of CuCl₂ with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes [Cu^II(bpy)Cu^I(CN)₃]_n, 1 (bpy = 2,2′-bipyridine) and {[Cu^II(tn)₂][Cu^I₄(CN)₆]}_n2 (tn = 1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (Cu^I and Cu^II centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC₄ pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN₅ slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ₃ coordination mode and bridges two Cu^I and one Cu^II ion, while the two other CN groups act as μ₂ bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably Cu^I centres, and Cu2 presumably Cu^II centres). The Cu2 ion presents centrosymmetric CuN₄ coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “[Cu^I(CN)]₆” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the [Cu(tn)₂]²⁺ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ = 0.239(1) K) of the Cu^II ions through the long and “a priori diamagnetic” –NC–Cu^I–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2.     

Electron localization induced by grain boundary disorder in the normal state of high-Tc superconductors

We have studied the effects of superconducting grain boundary disorder on the normal state transport properties of cuprate films. Dip-coated granular YBa₂Cu₃O_7−y (YBaCuO) thick films on polycrystalline MgO substrates were synthesized and networked grains were systematically made less disordered in order to probe the crossover from strong to weak inter-grain disorder. Grain boundary passivation was achieved by metallic inclusions of different forms. We have shown that the normal state of samples exhibit a semiconducting behavior and changes to ‘metallic’ with sharper transitions to the superconducting state as we reduce grain-interfaces disorder, i.e. increase metallic inclusion content. On the basis of electron localization mechanisms, the normal state conductivity is thus shown to undergo a dimensional crossover from 3D to 2D in the frame of the variable-range hopping (VRH) regime. The transition threshold was found to depend on the form of metallic inclusions.     

Fast pyrolysis of coals under N2 and CO2 atmospheres

Oxyfuel combustion represents one way for cleaner energy production using coal as combustible. The comparison between the oxycombustion and the conventional air combustion process starts with the investigation of the pyrolysis step. The aim of this contribution is to evaluate the impact of N₂ (for conventional air combustion) and CO₂ (for oxy-fuel combustion) atmospheres during pyrolysis of three different coals. The experiments are conducted in a drop tube furnace over a wide temperature range 800–1400 °C and for residence time ranging between 0.2 and 1.2 s. Coal devolatilized in N₂ and CO₂ atmospheres at low temperatures (?1200 °C) and longer residence times (>?0.5 s), the char-CO₂ reaction is clearly observed, whose intensity depends on the nature of the coal. Furthermore, the volatile yields are simulated using Kobayashi’s scheme and kinetic parameters are predicted for each coal. The char gasification under CO₂ is also accounted for by the model.