Ebrahim Abouzari-Lotf

Improved Methanol Barrier Property of Nafion Hybrid Membrane by Incorporating Nanofibrous Interlayer Self-Immobilized with High Level of Phosphotungstic Acid

High level of phosphotungstic acid (PWA) was self-immobilized on electrospun nylon nanofiberous sheet to fabricate highly selective methanol barrier layer for sandwich structured proton conducting membranes. Simple tuning for the assembly conditions of central layer and thickness of outer Nafion layers allowed obtaining different composite membranes with superior methanol barrier properties (namely, P=3.59×10(-8) cm2 s(-1)) coupled with proton conductivities reaching 58.6 mS cm(-1) at 30 °C. Comparable activation energy for proton transport and more than 20 times higher selectivity than Nafion 115 confirm the effectiveness of the central layer and resulting membranes for application in direct methanol fuel cells (DMFCs). When tested in DMFC single cell, the performance of hybrid membrane was far better than Nafion 115 especially at higher methanol concentrations.

Dioxin risk assessment: mechanisms of action and possible toxicity in human health

Dioxin-like compounds (DLCs) have been classified by the World Health Organization (WHO) as one of the most persistent toxic chemical substances in the environment, and they are associated with several occupational activities and industrial accidents around the world. Since the end of the 1970s, these toxic chemicals have been banned because of their human toxicity potential, long half-life, wide dispersion, and they bioaccumulate in the food web. This review serves as a primer for environmental health professionals to provide guidance on short-term risk assessment of dioxin and to identify key findings for health and exposure assessment based on policies of different agencies. It also presents possible health effects of dioxins, mechanisms of action, toxic equivalency factors (TEFs), and dose–response characterization. Key studies related to toxicity values of dioxin-like compounds and their possible human health risk were identified through PubMed and supplemented with relevant studies characterized by reviewing the reference lists in the review articles and primary literature. Existing data decreases the scope of analyses and models in relevant studies to a manageable size by focusing on the set of important studies related to the perspective of developing toxicity values of DLCs.

High refractive index and low-birefringence polyamides containing thiazole and naphthalene units

Highly refractive and solution processable polyamides (PAs) were synthesized by the introduction of thiazole rings, naphthalene groups, and thioether linkages. These PAs were synthesized by the polycondensation of a new diamine monomer, 5,5′-thiobis(2-amino-4-(2-naphthyl)thiazole) (DA), with various aromatic diacids. The bulky pendant naphthyl units endowed the resulting PAs with non-coplanar structures and excellent solubilities in organic solvents. The obtained PAs showed high thermal stability, with 10% weight loss temperatures exceeding 478 °C under nitrogen and 431 °C in air atmosphere, while their glass transition temperatures were in the range of 194–229 °C. The synergic effects of the thiazole groups, naphthyl substituents, and thioether linkages provided PAs with very high refractive indices of up to 1.7701 at 632.8 nm, along with small birefringences (<0.0076) and high Abbes numbers. The structure–property relationships of these PAs due to the presence of naphthyl substituents were also studied in detail by comparing the results with the previously reported analogous PAs.

Integrated ecological risk assessment of dioxin compounds

Current ecological risk assessment (ERA) schemes focus mainly on bioaccumulation and toxicity of pollutants in individual organisms. Ecological models are tools mainly used to assess ecological risks of pollutants to ecosystems, communities, and populations. Their main advantage is the relatively direct integration of the species sensitivity to organic pollutants, the fate and mechanism of action in the environment of toxicants, and life-history features of the individual organism of concern. To promote scientific consensus on ERA schemes, this review is intended to provide a guideline on short-term ERA involving dioxin chemicals and to identify key findings for exposure assessment based on policies of different agencies. It also presents possible adverse effects of dioxins on ecosystems, toxicity equivalence methodology, environmental fate and transport modeling, and development of stressor-response profiles for dioxin-like chemicals.

Nicotinic-based poly(amide-ether-imide)s: a new category of soluble, heat-resistant, and flame-retardant polyimides

A novel fully aromatic diamine containing highly pyridine units, amide, and ether groups was prepared via two-step reactions: nucleophilic substitution reaction of 2,6-diaminopyridine with 6-chloronicotinoyl chloride led to preparation of a dichloro-diamide compound. Subsequent reaction of this compound with 5-amino-1-naphthol resulted in synthesis of the particular diamine. After complete characterization, polycondensation reaction of the diamine with different dianhydrides led to preparation of related poly(amide-ether-imide)s. The polymers were characterized and their physical and thermal properties including viscosity, solubility, water absorption, thermal behavior and stability, flame retardancy, and crystallinity were studied. The nicotinic-based poly(amide-ether-imide)s showed high heat and flame resistant, low water absorption in conjunction with improved solubility in polar solvents.

Synthesis of pyrano[2,3-c]pyrazoles by ionic liquids under green and eco-safe conditions

Optimization of a green approach to the synthesis of pyrano[2,3-c]pyrazoles based on the one-pot, four-component condensation via a domino Knoevenagel/Michael/cyclization sequence was investigated. This method involved the evaluation of the activity of several ionic liquids (ILs) in various solvents. This one-pot, four-component reaction revealed simplicity, higher yield and lower toxicity advantages over a corresponding three-component method. The effect of reaction parameters including the type and amount of catalyst, type of solvent, reaction temperature and time were studied with respect to yield of pyrano[2,3-c]pyrazoles. Catalyst recyclability and time-saving aspects of the reaction suggest that this method presents real alternatives over conventional reaction protocols.

The Synthesis and Characterization of Novel Dibenzosulfide Diamine and the Application in the Determination of Heavy Metals

New 2,2′-thio-bis [4-methyl (2-amino phenoxy) phenyl ether] (IV) was synthesized. The structure of this compound was confirmed on IR, 1H, and 13C NMR data. A simple, efficient, and sensitive procedure is described for the spectrophotometric determination of a trace amount of Cd(II) or Co(II) in the presence of Zn(II) with this diamine.

Enhance protection of electronic appliances through multivariate modelling and optimization of ceramic core materials in varistor devices

E-waste comprises discarded low quality protected electronic appliances that annually accumulate million tons of hazardous materials in the environment. Protection is provided to control unwanted voltages that usually generate in associated electrical circuits by a multi-junction ceramic in a voltage dependent varistor. The ceramics microstructure consists of ZnO grains that are surrounded by the narrow boundaries of melted specific additives such as Bi2O3, TiO2 and Sb2O3. In fact, the boundaries manage the quality of protection through a certain volume of intrinsic oxygen vacancies transformation which depends on the amounts of the additives. Since these amounts are the ceramic fabrications initial input variables, the optimization process is capable of improving the quality of the protection (non-linear coefficient) as an output of the varistor devices. In this work, the fabrication was designed and then experimentally performed to calculate the non-linear coefficients of the produced varistors as actual responses. The responses were used to obtain an appropriate model for the fabrication by different semi-empirical methods. Afterward, the models predicted the optimized amounts of the additives which maximized the quality of the varistors. The predicted condition was fabricated as final varistors that were electrically characterized to compare their nonlinear coefficients as the quality indicator. The comparison demonstrated that the optimized amounts of Bi2O3 (0.5), TiO2 (0.47) and Sb2O3 (0.21) in mol% provided the very high protective varistor with nonlinear coefficients of 28.1. In conclusion, the optimization, which has industrial scale-up potential, warranties the electronic protection that controls global e-waste.

Spectrophotometric Study of Complexation of Tri-Aza Dibenzosulfide and Dibenzosulfoxide Macrocyclic Compounds with Heavy Metal Ions

The complexation reactions between 7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione ( TTD ) and 7,10,13-triaza-1-sulfoxo-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione ( TSD ) macrocycles with Ag+, Cd2+, Cu2+, Pb2+, Sr2+, Tl+, and Zn2+ ions have been studied in ethanol and methanol solutions at 25°C. The complexes formed between macrocycles ( TTD ) and ( TSD ) with these metals cations had a stiochiometry of 1:1 and 1:2, respectively. The stability constants of the resulting complexes were determined and found to decrease in the order Cu2+ > Zn2+ > Ag+ > Tl+ > Cd2+ > Pb2+ > Sr2+ with macrocycle ( TTD ) and Tl+ > Zn2+ > Cd2+ > Pb2+ > Cu2+ > Ag+ > Sr2+ with macrocycle ( TSD ).

Phase separated nanofibrous anion exchange membranes with polycationic side chains

Anion exchange membranes (AEMs) have gained significant interest in electrochemical energy devices with a unique set of benefits. However, none of the commercial AEMs behave ideally under alkaline operation conditions and developing appropriate membranes is one of the major hurdles to the durability and performance of anion exchange membrane fuel cells. Here we demonstrate a simple and efficient strategy of using nanofibrous materials, activated by radiation and functionalized with ionic groups to fabricate highly durable and conductive membranes with polycationic side chains. Two series of AEMs were prepared by radiation induced emulsion grafting of vinylbenzyl chloride onto syndiotactic polypropylene and nylon-66 nanofibrous sheets followed by crosslinking and introducing quaternary ammonium groups. A strong correlation was found between the choice of nanofibrous substrate as well as crosslinking degrees with water uptake, ion conductivity and stability of the membranes. A well-developed phase separated morphology was confirmed and the membranes with ion exchange capacities of 1.6–2.1 mmol g−1 showed high ionic conductivity, low methanol permeability and excellent alkaline stability. A hydroxide ion conductivity as high as 132 mS cm−1 was achieved at 80 °C and it was exceptionally retained at up to 90% after evaluation by accelerated degradation testing in 1 M NaOH at 80 °C for 672 h. A Pt-catalyzed fuel cell using these nanofibrous composite membranes showed a peak power density of above 120 mW cm−2 at 80 °C under 90% relative humidity. This strategy and observed properties pave the way for highly conductive and durable ion conducting membranes with tunable characteristics.