Tungstophosphoric acid nanoparticles supported on polyamic acid: A mild and recoverable heterogeneous catalyst for the selective synthesis of mono and bulky bis(1,8-dioxooctahydroxanthene)s under solvent-free conditions

A series of 1,8-dioxooctahydroxanthene derivatives and some crowded bis(1,8-dioxooctahdroxanthene) were selectively synthesized using tungstophosphoric acid nanoparticles supported on polyamic acid (TPA/PAA) as a new catalyst in solvent-free conditions. The high purity products were isolated and catalyst was easily separated in simple work-up and was recycled several times without loss of reactivity under the described reaction conditions. The reaction is characterized by short reaction time, high efficiency and environmentally friendly reaction conditions.     

Chemometric study of the aggregation of alcohol dehydrogenase and its suppression by beta-caseins: a mechanistic perspective

Molecular chaperones interact preferentially with certain aggregation-prone intermediates of target protein molecules. An estimation of the chaperone activity based on suppression of aggregation is required to be mechanistically understood. In this study, the multivariate curve resolution chemometric technique was applied on horse alcohol dehydrogenase (ADH) UV-spectra under thermal stress, to obtain the required information about the number and change in concentrations of the species involved. Chemometric analysis of UV-absorption spectra of horse ADH under thermal stress, led to the existence of three different molecular species including native (N), aggregation-prone intermediate (I) and final aggregate (A) species. Appearance and buildup of two molecular species I and A were connected to the disappearance of N-species. In the presence of β-caseins (BCN), however, a new complex between I and BCN (I-BCN) was formed. Meanwhile, by accretion of concentration of I-BCN complex, the light scattering intensity diminished. The data presented in this study clearly demonstrate that the interaction of BCN as a chaperone molecule with I-species takes place in a temperature-dependent manner and leads to a reversible I-BCN complex. In the absence of chaperones, I-state is subsequently converted to the final aggregate species. In the presence of BCN, this molecular species could be converted to the final aggregate state and/or form the I-BCN complex.     

A bucky gel consisting of Fe3O4 nanoparticles,graphene oxide and ionic liquid as an efficient sorbent for extraction of heavy metal ions from water prior to their determination by ICP-OES

Microchimica Acta - Bucky gels are gelatinous composite materials consisting of carbon nanotubes and ionic liquids. The authors describe the synthesis of a bucky gel containing Fe3O4 nanoparticles...     

Application of a nanostructured supramolecular solvent for the microextraction of diphenylamine and its mono‐nitrated derivatives from unburned single‐base propellants

A supramolecular solvent made up of nano‐sized inverted hexagonal aggregates of 1‐octanol is proposed for the microextraction of diphenylamine and its mono‐nitrated derivatives in unburned single‐base propellants. The procedure included the extraction of sub‐gram quantities (30 mg) of homogenized propellant with 1.5 mL of the supramolecular solvent. Several conditions affecting extraction efficiency, for example the concentrations of the major components of the supramolecular solvent (tetrahydrofuran and alkanol), alkanol type, solvent pH, and extraction time, were investigated and optimized. The main forces for the microextraction of analytes in the nanostructured supramolecular solvent include both dispersion and hydrogen bond interactions. This mixed‐mode mechanism resulted in high extraction efficiencies reaching low method detection limits (0.005–0.012 mg/g) without the need for extract evaporation. Under the optimum conditions, recoveries in samples ranged between about 82.6 and 98.7%. Compared to the reference method, the proposed method is simple and rapid, delivering accurate and precise results, and can be applied for routine determination of diphenylamine and its derivatives in propellants. The precision of the method, expressed as relative standard deviation, was about 4.3–10.9%.     

Ultrasound-assisted emulsification microextraction method based on applying low density organic solvents followed by gas chromatography analysis for the determination of polycyclic aromatic hydrocarbons in water samples

In this study, a fast, simple and efficient ultrasound-assisted emulsification microextraction (USAEME) method was successfully developed based on applying low density organic solvents. Fourteen microliters of toluene was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample that was located inside the ultrasonic water bath. The formed emulsion was centrifuged and 2 μL of separated toluene (about 4 μL) was injected into a gas chromatographic system equipped with a flame ionization detector (GC-FID) for analysis. Some polycyclic aromatic hydrocarbons (PAHs) were selected as model compounds for developing the method and evaluating its performance and to compare the efficiency of the proposed method with previously reported techniques. Several factors influencing the emulsification, extraction and collection efficiency such as the nature and volume of organic solvent, emulsification–extraction temperature, ionic strength and equilibrium and centrifugation times were investigated and optimized. Under the optimum conditions, preconcentration factors (PFs) in a range of 1776–2714 were obtained. The performance of the proposed method was studied in terms of linear dynamic range (LDRs from 0.05 to 100 μg L⁻¹), linearity (R² ≥ 0.994), precision (repeatability: RSD% ≤ 7.9, reproducibility: RSD% ≤ 14.6) and extraction percents (59.2–90.5%). Limits of detection (LODs) in the range of 0.02–0.05 μg L⁻¹ were obtained for different PAHs. The applicability of the proposed method was evaluated by the extraction and determination of PAHs from several natural water samples.     

SnCl2/nano SiO2：A green and reusable heterogeneous catalyst for the synthesis of polyfunctionalized 4H-pyrans

A highly efficient and general method for the synthesis of polyfunctionalized 4H-pyrans is established through a one-pot multicomponent cyclocondensation of aromatic aldehydes with CH acids, malononitrile and ethyl acetoacetate using nano silica supported tin (Ⅱ) chloride as a catalyst. In this method SnCl2/nano SiO2 was used as green and reusable catalyst. Excellent yields, short reaction times, simple workup, and inexpensiveness and commercially availability of the catalyst are the advantages of this method.     

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.