Gas chromatographic technique for determination of Irgafos 168 in polyolefin samples after conversion to the related phenolic compound by saponification

A gas chromatographic technique is reported for the determination of a secondary antioxidant, Irgafos 168, in polymeric samples. Irgafos 168 [tris(2,4-di-tert-butyl phenyl)phosphite] is extracted by dissolution/precipitation, saponified to 2,4-di-tert-butyl phenol by refluxing in the presence of methanolic potassium hydroxide, and determined by gas chromatography-flame ionization detection. The method’s repeatability is good, and the relative standard deviation is 7.5% (between runs) and 15.5% (between days). This method was applied to the determination of Irgafos 168 in commercial polymers, and the obtained results were in relatively good agreement with those obtained by the previously reported spectrophotometric method. Correspondence: Mir Ali Farajzadeh, Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran     

Enhanced lithium electrochemical performance and optical properties of CeO<Subscript>2</Subscript>–SnO<Subscript>2</Subscript> nanocomposite thin films by transition metal (TM: Ni,Mn, and Co) doping

Undoped and transition metal (TM: Ni, Mn, Co)-doped CeO₂–SnO₂ nanocomposite thin films were prepared by sol-gel dip coating (SGDC) technique. The grazing incidence X-ray diffraction (GIXRD) patterns indicated that CeO₂–SnO₂ film has a cubic structure of CeO₂ and the crystallinity deteriorated with incorporation of dopant. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed that the surface morphology of the films was affected by TM incorporation. The surface roughness and fractal dimensions of CeO₂–SnO₂ films increased with doping. The average transmittance of CeO₂–SnO₂ thin film is found nearly 80% in the visible region and increased with doping. The absorption edge revealed a blue shift toward shorter wavelengths after incorporation of TM ions. The compositional dependence of optical parameters such as refractive index, extinction coefficient, and optical conductivity were also investigated. Cyclic voltammetry measurements showed that ion storage capacity was decreased significantly with increasing scan rate. The undoped and doped CeO₂–SnO₂ films showed good reversible cycle of intercalation/deintercalation of Li⁺ ions. The ion storage capacity and electrochemical stability were enhanced with transition metal doping. The Mn-doped CeO₂–SnO₂ composite thin film had better ion storage capacity rather than other samples due to its special porous morphology. The Li diffusion toward electrode surface was described in terms of self-similar fractal dimension. A quenching in blue-green photoluminescence (PL) intensity of CeO₂–SnO₂ films was occurred by transition metal doping.

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New Triazinoindole Bearing Benzimidazole/Benzoxazole Hybrids Analogs as Potent Inhibitors of Urease: Synthesis,In Vitro Analysis and Molecular Docking Studies

Twenty-four analogs based on triazinoindole bearing benzimidazole/benzoxazole moieties (1–25) were synthesized. Utilizing a variety of spectroscopic methods, including ¹H-, ¹³C-NMR, and HREI-MS, the newly afforded compounds (1–25) were analyzed. The synthesized analogs were tested against urease enzyme (in vitro) as compared to the standard thiourea drug. All triazinoindole-based benzimidazole/benzoxazole analogs (1–25) exhibited moderate to excellent inhibition profiles, having IC₅₀ values of 0.20 ± 0.01 to 36.20 ± 0.70 μM when evaluated under the positive control of thiourea as a standard drug. To better understand the structure–activity relationship, the synthesized compounds were split into two groups, “A” and “B.” Among category “A” analogs, analogs 8 (bearing tri-hydroxy substitutions at the 2,4,6-position of aryl ring C) and 5 (bearing di-hydroxy substitutions at the 3,4-position of aryl ring C) emerged as the most potent inhibitors of urease enzyme and displayed many times more potency than a standard thiourea drug. Besides that, analog 22 (which holds di-hydroxy substitutions at the 2,3-position of the aryl ring) and analog 23 (bearing ortho-fluoro substitution) showed ten-fold-enhanced inhibitory potential compared to standard thiourea among category “B” analogs. Molecular docking studies on the active analogs of each category were performed; the results obtained revealed that the presence of hydroxy and fluoro-substitutions on different positions of aryl ring C play a pivotal role in binding interactions with the active site of the targeted urease enzyme.     

Synthesis,In Vitro Anti-Microbial Analysis and Molecular Docking Study of Aliphatic Hydrazide-Based Benzene Sulphonamide Derivatives as Potent Inhibitors of α-Glucosidase and Urease

A unique series of sulphonamide derivatives was attempted to be synthesized in this study using a new and effective method. All of the synthesized compounds were verified using several spectroscopic methods, including FTIR, ¹H-NMR, ¹³C-NMR, and HREI-MS, and their binding interactions were studied using molecular docking. The enzymes urease and α-glucosidase were evaluated against each derivative (1–15). When compared to their respective standard drug such as acarbose and thiourea, almost all compounds were shown to have excellent activity. Among the screened series, analogs 5 (IC₅₀ = 3.20 ± 0.40 and 2.10 ± 0.10 µM) and 6 (IC₅₀ = 2.50 ± 0.40 and 5.30 ± 0.20 µM), emerged as potent molecules when compared to the standard drugs acarbose (IC₅₀ = 8.24 ± 0.08 µM) and urease (IC₅₀ = 7.80 ± 0.30). Moreover, an anti-microbial study also demonstrated that analogs 5 and 6 were found with minimum inhibitory concentrations (MICs) in the presence of standard drugs streptomycin and terinafine.     

A theoretical practice on grazing‐exit energy dispersive X‐ray spectroscopy as a surface analysis strategy to investigate BiVO4 nano‐films

In the current work, a thin film of bismuth vanadate was defined over a silicon substrate, and a calculative Monte Carlo approach was followed to achieve the best grazing‐exit angle to acquire compositional data from top few nanometers of surface. This strategy is very beneficial in order to increase X‐ray signals originated from surface and diminish the background X‐ray signals started off from the substrate. In this regard, grazing‐exit energy dispersive X‐ray spectroscopy can be considered as an accessible and economical analytical tool to investigate thin films and nano‐layers. The major advantage of this method is that just by applying a re‐arrangement in a scanning electron microscope, it can be used to study compositional properties of thin layers. In this contribution, a theoretical approach using Monte Carlo models was used to simulate the behavior of electron beams impinging onto BiVO₄ nano‐layers with thickness of 50 nm and electron trajectories inside the film. Characteristic X‐rays and spatial energy distribution of the backscattered electrons were also calculated. Under grazing‐exit angle of around 0.5°, the best surface signal/background noise ratio was achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

Kinetic modeling of pyrolysis of scrap tires

The disposal of used tires is a major environmental problem. With increasing interest on recovery of wastes, pyrolysis is considered as an alternative process for recovering some of the value in scrap tires. An accurate kinetic model is required to predict product yields during thermal or catalytic pyrolysis of scrap tires. Pyrolysis products contain a variety of hydrocarbons over a wide boiling range. A common approach for kinetic modeling of such complex systems is lumping where each lump is defined by a boiling point range. Available experimental data for thermal and catalytic pyrolysis of scrap tires from the literature were used to evaluate two types of lumping models; discrete and continuous lumping models. The lumps were described in terms of the boiling point distribution of the reactant mixture. In the discrete model, the conversion of heavier to lighter lumps was described in terms of series and parallel first order reactions. In the continuous model, the normalized boiling point was used to describe the reactant mixture as a continuous mixture. An optimization procedure was implemented for estimation of the model parameters using experimental data reported in the literature. Model predictions with indicated that although the discrete model could reasonably predict the yields of different cuts in the products, predictions of the continuous model were very good, especially in thermal pyrolysis.     

Electrochemical performance of spindle-like Fe2Co-MOF and derived magnetic yolk-shell CoFe2O4 microspheres for supercapacitor applications

Nanostructured cobalt ferrite (CoFe₂O₄) has been synthesized by a two-step process, a facile ultrasonic-assisted solvothermal technique for Fe₂Co-MOF preparation and subsequent calcination. X-ray diffraction (XRD) patterns confirm the formation of MIL-88A(Fe) structure of Fe₂Co-MOF and the cubic spinel structure of CoFe₂O₄. Field emission scanning electron microscope (FESEM) images reveal that calcination process converts the spindle-like morphology of Fe₂Co-MOF to yolk-shell CoFe₂O₄ microspheres. From Brunauer–Emmett–Teller (BET) analysis, the specific surface areas of 36.0 and 29.2 m² g^?1 are measured for Fe₂Co-MOF and CoFe₂O₄, respectively. Vibrating sample magnetometer (VSM) analysis of CoFe₂O₄ displays high coercivity of 2500 Oe due to surface anisotropy. Conversion of Fe₂Co-MOF to CoFe₂O₄ reduces the optical band gap from 1.92 to 1.77 eV. Electrochemical performance of Fe₂Co-MOF and CoFe₂O₄ deposited on Ni foams (NFs) is examined by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests. Specific capacitances of 489.9 and 192.6 F g^?1 have been achieved from GCD curves at a current density of 1 A g^?1 for Fe₂Co-MOF/NF and CoFe₂O₄/NF electrodes, respectively. Fe₂Co-MOF/NF electrode exhibits more cyclic stability than CoFe₂O₄/NF electrode after 3000 cycles.

     

The role of nickel addition and annealing temperature on ion storage performance of nanostructured nickel ferrite thin films

The sol–gel spin-coated nickel ferrite (NF), NiFe₂O₄, thin films were synthesised and the effect of annealing temperature and compositional ratio on different properties of samples were investigated. Electrochemical performance of the films was measured in the presence of KOH and LiClO₄/PC electrolyte. Generally, addition of nickel increases the current density. The NF thin films with molar ratio of 0.5 and annealed at 400 °C have the highest charge density value and the highest capacitance in both electrolytes. Annealing temperature had significant effect on electrochemical properties of NF thin films and the diffusion coefficient enhanced by increasing the annealing temperature. X-ray diffraction patterns of prepared samples showed the rhombohedral structure, hematite phase (α-Fe₂O₃), of iron oxide sample and the presence of inverse spinel structure confirms the formation of NF. Field emission scanning electron microscopy images revealed that the morphology of films changes from larvae shape to granular structure by nickel incorporation and the grain size increased by raising the annealing temperature. The absorption edge of the hematite shift to higher wavelength by annealing and nickel incorporation and band gap narrowing has been occurred.