Evaluation of mechanical properties and characterization of silicon carbide–reinforced polyamide 6 polymer composites and their engineering applications

In this article, the tensile strength, impact, and hardness properties of silicon carbide (SiC) reinforced with polyamide 6 (PA6) are described for the first time. The composites were fabricated by an injection molding method using the SiC with varying weight percentages. The tensile and hardness of SiC/PA6 composites showed a regular trend of increasing tensile strength, impact, and hardness properties with varying weight percentages until 10 wt% and impact strength of SiC/PA6 composites increased up to 5 wt% afterwards decreasing the mechanical properties of the composite with greater weight percentages. Scanning electron microscope (SEM) studies were carried out to evaluate the SiC/PA6 interactions. The results related to SiC/PA6 composites were compared with those obtained for pure PA6.     

A multicomponent,solvent-free,one-pot synthesis of benzoxanthenones catalyzed by HY zeolite: their anti-microbial and cell imaging studies

An atom-economical, multicomponent condensation of naphthols, aldehydes, and cyclic 1,3-dicarbonyl compounds catalyzed by HY zeolites under solvent-free conditions is reported. This ecofriendly protocol offers several advantages such as a green and cost-effective procedure with excellent yield, shorter reaction time, simpler work-up, recovery, and reusability of metal-free solid acid heterogeneous catalyst and tolerance of a wide range of functional groups. The biological studies such as in vitro anti-microbial activities of the prepared new compounds and cell imaging studies on K562 leukemia cell lines by selected benzoxanthenones are evaluated.     

Zn-K10-clay (clayzic) as an efficient water-tolerant, solid acid catalyst for the synthesis of benzimidazoles and quinoxalines at room temperature

A very simple, green and efficient protocol is developed in which zinc chloride-exchanged K10-montmorillonite (clayzic) is employed as a Lewis acid catalyst in aqueous media at room temperature for the synthesis of various benzimidazoles and quinoxalines from carbonyl compounds and o-phenylenediamine. Among the various catalysts (including claycop and Zn²⁺-Y) studied, clayzic produces benzimidazoles and quinoxalines in higher yield, and with a flexible diamine such as ethylenediamine only the bis-Schiff base is formed. Other salient features of this protocol include milder conditions, atom-economy, absence of coupling agents, and no wastes.     

Effect of external pressure on Tc of as‐grown and thermally treated superconducting Rbx Fe2–ySe2 single crystals

We report on the effect of external pressure on the superconducting transition temperature (T_c) of as‐grown and thermally treated single crystals of superconducting iron chalcogenide Rb_0.85Fe_1.9Se₂. The superconducting transition temperature of 27.1 K at ambient pressure for the as‐grown sample was found to increase up to 33.2 K for the sample annealed for 3 h at 215 °C in vacuum. An increase of T_c up to 28.2 K was observed for the as‐grown sample at a pressure of 0.83 GPa. For all the studied crystals, annealed in the temperature range between 215 °C and 290 °C, the external pressure seems to decrease the superconducting transition temperature and a negative pressure coefficient of T_c was observed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterization and optimization of Ce0.6Zr0.4−x Mn x O2 (x ≤ 0.4)

In situ synthesis method is used to synthesize g-C₃N₄-P25 composite photocatalysts with different mass rations. The experiment result shows that P25 particles with diameter at range of 20–30 nm were embedded homogenously in the sheets of g-C₃N₄. Coupling g-C₃N₄ with P25 can not only improve the visible light absorption, but also improve the visible light photocatalytic activity of P25. The g-C₃N₄-P25 nanocomposite has the higher photocatalytic activity than g-C₃N₄ under visible light. The optimal g-C₃N₄ content with the highest photocatalytic activity is determined to be 84 %, which is almost 3.3 times higher than that of individual g-C₃N₄ under the visible light. The enhanced visible light photocatalytic activity could be ascribed to the formation of g-C₃N₄ and TiO₂ heteojunction, which results in an efficient separation and transfer of photo-induced charge carriers. The electron spin resonance results show that the ^·O₂ ^? radicals are main active species for g-C₃N₄ and the g-C₃N₄-P25 nanocomposites.     

Enzyme-Mediated Bacterial Biodegradation of an Azo Dye (C.I. Acid Blue 113): Reuse of Treated Dye Wastewater in Post-Tanning Operations

“Dyeing” is a common practice used to color the hides during the post-tanning operations in leather processing generating plenty of wastewater. The waste stream containing dye as pollutant is severely harmful to living beings. An azo dye (C.I. Acid Blue 113) has been biodegraded effectively by bacterial culture mediated with azoreductase enzyme to reduce the pollution load in the present investigation. The maximum rate of dye degradation was found to be 96?±?4 and 92?±?4 % for the initial concentrations of 100 and 200 mg/l, respectively. The enzyme activity was measured using NADH as a substrate. Fourier transform infrared spectroscopy (FT-IR) analysis was confirmed that the transformation of azo linkage could be transformed into N₂ or NH₃ or incorporated into complete biomass. Breaking down of dye molecules to various metabolites (such as aniline, naphthalene-1,4-diamine, 3-aminobenzenesulfonic acid, naphthalene-1-sulfonic acid, 8-aminonaphthalene-1-sulfonic acid, 5,8-diaminonaphthalene-1-sulfonic acid) was confirmed by gas chromatography and mass spectra (GC-MS) and mass (electrospray ionization (ESI)) spectra analysis. The treated wastewater could be reused for dyeing operation in the leather processing, and the properties of produced leather were evaluated by conventional methods that revealed to have improved dye penetration into the grain layer of experimental leather sample and resulted in high levelness of dyeing, which helps to obtain the desired smoothness and soft leather properties.     

Michael addition of indoles to β-nitrostyrenes catalyzed by HY zeolite under solvent-free conditions

Michael addition of indoles to β-nitrostyrenes is reported using HY zeolite as catalyst under mild reaction conditions. This methodology allows the synthesis of various indole derivatives in good to high yields at 50 °C under solvent-free conditions. The short reaction time and achieving high yield of the desired products are the main advantages of the present work. The catalyst can be easily recovered and reused for six successive runs without considerable changes in yields. This Michael addition catalyzed by HY zeolite is operationally simple and can be considered as a greener protocol as it avoids the use of corrosive acids and toxic reagents.     

Highly Selective “Turn‐On” Fluorescent and Colorimetric Sensing of Fluoride Ion Using 2‐(2‐Hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one based on Excited‐State Proton Transfer

A simple, highly selective and sensitive colorimetric system for the detection of fluoride ion in an aqueous medium has been developed using 2‐(2‐hydroxyphenyl)‐2,3‐dihydroquinolin‐4(1 H)‐one. This system allows selective “turn‐on” fluorescence detection of fluoride ion, which is found to be dependent upon guest basicity. An excited‐state proton transfer is proposed to be the signaling mechanism, which is rationalized by DFT and TD‐DFT calculations. The present sensor can also be applied to detect fluoride levels in real water samples.