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.     

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.     

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.

     

Multiple N—H...NC,C—H...NC and nitrile...π interactions in 4,4′‐bipyridine‐1,1′‐diium bis(1,1,3,3‐tetracyano‐2‐ethoxypropenide): structure determination and DFT calculations of anion...π cation interaction energies

Polynitrile anions are important in both coordination chemistry and molecular materials chemistry, and are interesting for their extensive electronic delocalization. The title compound crystallizes with two symmetry‐independent half 4,4′‐bipyridine‐1,1′‐diium (bpyH₂²⁺) cations and two symmetry‐independent 1,1,3,3‐tetracyano‐2‐ethoxypropenide (tcnoet⁻) anions in the asymmetric unit. One of the bpyH₂²⁺ ions is located on a crystallographic twofold rotation axis (canted pyridine rings) and the other is located on a crystallographic inversion center (coplanar pyridine rings). The ethyl group of one of the tcnoet⁻ anions is disordered over two sites with equal populations. The extended structure exhibits two separate N—H...NC hydrogen‐bonding motifs, which result in a sheet structure parallel to (010), and weak C—H...NC hydrogen bonds form joined rings. Two types of multicenter CN...π interactions are observed between the bpyH₂²⁺ rings and tcnoet⁻ anions. An additonal CN...π interaction between adjacent tcnoet⁻ anions is observed. Using density functional theory, the calculated attractive energy between cation and anion pairs in the tcnoet⁻...π(bipyridinediium) interactions were found to be 557 and 612 kJ mol⁻¹ for coplanar and canted bpyH₂²⁺ cations, respectively.