High electrochemical stability of polyvinylidene fluoride (PVDF) porous membranes using phase inversion methods for lithium-ion batteries

Journal of Solid State Electrochemistry - Polyvinylidene fluoride (PVDF) porous membranes were prepared by non-solvent-induced phase separation (NIPS) method. The membranes were made by different...     

Amplitudes with different helicity configurations of noncommutative QED

The amplitudes of purely photon processes of noncommutative QED (NCQED) are derived for different helicity configurations of photons. The basic ingredient is the NCQED counterpart of the Yang–Mills recursion relations by means of Berends and Giele. The explicit solutions of recursion relations for NCQED photon current with special helicity configurations and also recursion relations for the NCQED fermion–photon current with special helicity configurations of photons (all photons have plus helicity) are presented.     

Diaminobisbenzothiazole chain extended polyurethanes as a novel class of thermoplastic polyurethane elastomers with improved thermal stability and electrical insulation properties

This work was devoted to the development of a new class of modified polyurethane as an electrical insulating material. For this purpose, NCO‐terminated urethane prepolymers at different NCO contents were prepared and chain extended by 6,6′‐oxybis(2‐aminobenzothiazole) (ABT) to produce thermoplastic polyurethane elastomers. All of the polymers were characterized by FTIR and ¹HNMR spectroscopies and examined for their thermal, mechanical, and electrical properties. The dynamic mechanical measurements results showed two glass transitions indicating phase separation. A considerable improvement in the thermal and electrical properties in comparison to common polyurethanes was detected for these polymers. The level of enhancement in the measured properties was related to the polyol molecular weight, hard segment content, and consequently the amount of the introduced urea and benzothiazole moieties. These findings indicated the improved high service temperature performance of these materials as electrical insulator for metallic surfaces. Copyright © 2008 John Wiley & Sons, Ltd.     

New Model for Polymerization of Oligomeric Alcohol Dehydrogenases into Nanoaggregates

Polymerization and self-assembly of proteins into nanoaggregates of different sizes and morphologies (nanoensembles or nanofilaments) is a phenomenon that involved problems in various neurodegenerative diseases (medicine) and enzyme instability/inactivity (biotechnology). Thermal polymerization of horse liver alcohol dehydrogenase (dimeric) and yeast alcohol dehydrogenase (tetrameric), as biotechnological ADH representative enzymes, was evaluated for the development of a rational strategy to control aggregation. Constructed ADH nuclei, which grew to larger amorphous nanoaggregates, were prevented via high repulsion strain of the net charge values. Good correlation between the variation in scattering and λ ⁻² was related to the amorphousness of the nanoaggregated ADHs, shown by electron microscopic images. Scattering corrections revealed that ADH polymerization was related to the quaternary structural changes, including delocalization of subunits without unfolding, i.e. lacking the 3D conformational and/or secondary-ordered structural changes. The results demonstrated that electrostatic repulsion was not only responsible for disaggregation but also caused a delay in the onset of aggregation temperature, decreasing maximum values of aggregation and amounts of precipitation. Together, our results demonstrate and propose a new model of self-assembly for ADH enzymes based on the construction of nuclei, which grow to formless nanoaggregates with minimal changes in the tertiary and secondary conformations.     

Ionic liquid based dispersive liquid-liquid microextraction combined with ICP-OES for the determination of trace quantities of cobalt, copper, manganese, nickel and zinc in environmental water samples

We describe a method for ionic liquid based dispersive liquid-liquid microextraction of Co(II), Cu(II), Mn(II), Ni(II) and Zn(II), followed by their determination via flow injection inductively coupled plasma optical emission spectrometry. The method is making use of the complexing agent 1-(2-thenoyl)-3,3,3-trifluoracetone, the ionic liquid 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide, and of ethanol as the dispersing solvent. After extraction and preconcentration, the sedimented ionic liquid (containing the target analytes) is collected, diluted with 1-propanol, and introduced to the ICP-OES. Effects of pH, ionic strength, ligand to metal molar ratio, volumes of extraction and disperser solvents on the performance of the microextraction were optimized in a half-fractional factorial design. The significant parameters were optimized using a face-centered central composite design. The method has detection limits between 0.10 and 0.20?ng?mL^?1 of the metal ions, preconcentration factors between 79 and 102, linear responses in 0.25 to 200?ng?mL^?1 concentration ranges, and relative standard deviations of 3.4 to 6.0%. The method was successfully applied to the analysis of drinking water, a fish farming pond water, and waste water from an industrial complex.

Characterization of a Redox-responsive Molecular Switch Based on Dibenzo[1,2]dithiine Using DFT

Structural and electronic properties of a bistable redox-responsive molecular switch based on dibenzo[1,2]dithiine (PSBH) were studied using the DFT-B3LYP/6-31G* method. The results confirmed that the electrical conductivity of the closed form of considered molecular switch is higher than that of the open form. NBO electric charges on heavy atoms of biphenyl unit revealed that the positive charge on sulfur atoms reinforced, which caused the collapse of disulfide bond.     

Dispersive liquid–liquid microextraction based on the solidification of floating organic drop followed by inductively coupled plasma-optical emission spectrometry as a fast technique for the simultaneous determination of heavy metals

A simple, rapid and efficient dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME–SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA₁₆ (4⁵) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140 μL of 1-undecanol; disperser solvent: 2.0 mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5–250 μg L⁻¹ for Mn, 1.25–250 μg L⁻¹ for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3 μg L⁻¹. Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained.     

Chemical speciation and contamination assessment of Zn and Cd by sequential extraction in surface sediment of Klang River, Malaysia

The concentration and chemical speciation of Cd and Zn as well as total organic carbon (TOC) were studied in surface sediments from 21 stations along Klang River. Sequential extraction technique (SET) was applied to assess the four (exchangeable, acid-reducible, oxidisable-organic and residual) fractions in surface sediment. And also, to obtain an overall classification of cadmium and zinc pollution in this area. This investigation was the first study on the basis of the chemical speciation of Cd and Zn in surface sediments of the Klang River. The total concentrations of metals were ranged (0.60–2.26 µg g^{− 1}) for Cd and (33.26–268.24 µg g^{− 1}) for Zn. The chemical speciation of Cd and Zn in most sampling stations were in the order of residual > acid-reducible > oxidisable-organic > exchangeable, and it showed that the Zn in Klang River surface sediments existed in the nonresistant fractions, whilst Cd existed in the resistant fraction. The degree of surface sediments contamination was determined for individual contamination factors (ICF) and global contamination factor (GCF). The result of ICF and GCF values showed that those stations located vicinity of municipal area had high potential risk to fauna and flora of the Klang River. The relationship between the concentration of cadmium and zinc at the oxidation-organic fraction with TOC in surface sediment was identified. The results showed that TOC had a positive function to complex with Cd and Zn in the surface sediment of Klang River.     

Convenient and Efficient Method for the Synthesis of N-Heteroaryl Aminonaphthols under Solvent-Free Conditions

A convenient, efficient and green synthesis of N‐heteroaryl aminonaphthols has been developed by one‐pot, three‐component condensation of β‐naphthol, heteroaryl amines and substituted benzaldehydes under solvent‐free conditions at elevated temperature. The advantages of these reactions are simplicity of the reaction procedure, short reaction times, simple work‐up, catalyst‐free conditions and pure products in good to excellent yields.