Metastable and stable pitting events at zinc passive layer in alkaline solutions

The electrochemical behavior of Zn in 0.5 M NaOH solutions containing various concentrations (0.01–0.1 M) of ClO₃ ^? or ClO₄ ^? anions was studied with potentiodynamic anodic polarization and chronoamperometry techniques. Microstructural and topographical characterization of the pitted surfaces was carried out by ex situ scanning electron microscopy and atomic force microscopy examinations. Addition of either ClO₃ ^? or ClO₄ ^? stimulated general corrosion and ruptured the passive layer (stable pitting), with ClO₃ ^? being more aggressive than ClO₄ ^?. Metastable pitting events appear as current oscillations (spikes) at potentials close to the pitting potential when Cl^? ions are produced by cathodic reduction of ClO₃ ^? and ClO₄ ^? before passive layer growth. Current–time measurements are performed at fixed potential after production of Cl^? ions and show that the rate of metastable pitting and the intensity of current spikes increase with the potential and the concentration of aggressive anions. Concepts of thin film growth are applied to the passive layer formation in order to explain those results. Metastable events are related to the presence of defects in the passive layer because their frequency and intensity are enhanced in conditions that favor defect formation and roughening in growing films, while stable pitting typically occurs at regions of high metal disorder.     

Evaluation of Antifungal and Antioxidant Activity of Newly Synthesized 4‐Thiazolidinones

The antifungal and antioxidant activities of thirty newly synthesized 4‐thiazolidinone (TZON) derivatives were assessed against some fungal species including Candida albicans and Aspergillus niger. The introduction of different arylidene moieties at 5‐positions of the thiazolidinone ring successfully enhanced its biological activity. The structure–activity relationships revealed that 4‐thiazolidinone derivatives harboring dicarboxyethyl (at the 2‐ethenyl) and p‐nitrophenylhydrazyl arm (at the 5‐arylidine positions of the thiazolidinone ring) display considerable antifungal and antioxidant properties.     

Corrosion inhibition of zinc in aqueous acidic media using a novel synthesized Schiff base – an experimental and theoretical study

Abstract

The kinetics of H₂ production during Zn corrosion in 0.5?M HCl without and with various additives of N,N'-bis-(1-hydroxyphenylimine)-2,5-thiophenedicarboxaldehyde (HPTD) was studied using gasometry and electrochemical techniques. The surface of the corroded Zn samples was investigated using SEM and Optical Profilometry. The rate of H₂ production (RHP) increased with the immersion time and temperature. Presence of HPTD mitigated RHP due to an adsorption process. The electrochemical impedance spectroscopy showed that HPTD had a good inhibitive effect. Polarization data proved that HPTD acted as a surface-active mixed-type inhibitor. Some thermodynamic parameters were deduced and discussed. Theoretical calculations were also conducted to corroborate the capability of HPTD to protect Zn surface from corrosion process.     

Statistical and Mathematical Investigations for Determining the Binding Constants of Micelle with Reactants Molecules from Kinetic Data

Binding constants between reactants molecules with micelles are considered to be important parameters particularly in micellar catalysis area. Recently, we developed a statistical method based on multiple linear regression for determining those parameters from kinetic data (Phys. Chem. Liq. 2008, 46, 34–46). In the present work, we derived further two statistical equations from the same original equation using also multiple linear regression method. A substantial difference has been found between the results of those equations and with that of the recently published one. This strongly indicates that the statistical procedures are not valid for such a purpose, that is, the available statistical and graphical methods in the literature are also not suitable for such treatment. A mathematical procedure using iterative method for evaluating the binding constants is introduced. An equation for such treatment has also been derived from the same original equation, and a computer program for this purpose has been written. Application of the developed method to the kinetic data has been found to be quite successful. It has been concluded that the presented mathematical method is simple, reliable, and accurate.     

Synthesis,Characterization, and Antimicrobial Activity of Carboxymethyl Chitosan-Graft-Poly(N-acryloyl,N′-cyanoacetohydrazide) Copolymers

Carboxymethyl chitosan was grafted with N-acryloyl,N′-cyanoacetohydrazide in homogenous aqueous phase using potassium persulfate initiator. The maximum grafting yield achieved was 448% at 0.03 mol/L potassium persulfate, 0.75 mol/L N-acryloyl,N′-cyanoacetohydrazide, and 60°C within 2 h. The grafted copolymers showed better thermal stability than that of carboxymethyl chitosan. The samples with percent grafting values up to 98% were soluble in water, but a higher grafting extent resulted in insoluble copolymers. The grafted copolymers are nontoxic materials and showed an inhibition effect on both Escherichia coli and Staphylococcus aureus bacteria and Aspergillus flavus and Candida albicans fungi better than those of chitosan and carboxymethyl chitosan themselves.     

Synthesis of some new pyrimidine derivatives and evaluation of their anticancer and antibacterial activities

Starting from the reaction of ethyl cyanoacetate with thiourea and the appropriate aldehydes, a series of new pyrimidine derivatives were prepared. Ten selected pyrimidine derivatives were subjected to a screening system for the investigation of their antitumor potency against liver (HEPG2) cell line. The antitumor activity results indicated that most of the selected pyrimidine derivatives showed moderate growth inhibition activity against the tested cell line, but with varying intensities in comparison to the known anticancer drugs: 5-fluorouracil and doxorubicin. Some of the synthesized compounds were also tested for their antimicrobial activity against bacteria as well as fungal isolates.     

Flexible carbon nanostructures with electrospun nickel oxide as a lithium-ion battery anode

Carbon nanostructures (CNS) with high electrical conductivity and unique branched structure of carbon nanotubes combined with NiO nanofibers (NFs) were used as anode for lithium-ion batteries. CNS works as a framework substrate for the anodic conversion reaction of nickel oxide (NiO). Electrochemical performance and behavior of CNS/NiO anodes is compared with the conventional carbon (C)/NiO anodes. CNS/NiO NF-based anode retains high specific capacity under different current densities compared to C/NiO anode. Moreover, specific capacity as high as 450 mAh/g for CNS/NiO NF anode is observed compared to only 90 mAh/g for C/NiO NFs using a current density of 500 mA/g after 500 cycles. This improved performance is attributed to the highly conductive network of CNS leading to efficient charge transfer. The high porosity, electrical conductivity as well as the branched and networked nature of CNS reveal to be of critical importance to allow the electrochemical conversion reactions.     

Design,Synthesis, and Molecular Docking of Paracyclophanyl-Thiazole Hybrids as Novel CDK1 Inhibitors and Apoptosis Inducing Anti-Melanoma Agents

Three new series of paracyclophanyl-dihydronaphtho[2,3-d]thiazoles and paracyclophanyl-thiazolium bromides were designed, synthesized, and characterized by their spectroscopic data, along with X-ray analysis. One-dose assay results of anticancer activity indicated that 3a–e had the highest ability to inhibit the proliferation of different cancer cell lines. Moreover, the hybrids 3c–e were selected for five-dose analyses to demonstrate a broad spectrum of antitumor activity without apparent selectivity. Interestingly, series I compounds (Z)-N-substituted-4,9-dihydronaphtho[2,3-d]thiazol-3(2H)-yl)-4′-[2.2]paracyclophanylamide) that are carrying 1,4-dihydronaphthoquinone were more active as antiproliferative agents than their naphthalene-containing congeners (series II: substituted 2-(4′-[2.2]paracyclophanyl)hydrazinyl)-4-(naphth-2-yl)-thiazol-3-ium bromide hybrids) and (series III: 3-(4′-[2.2]paracyclophanyl)amido-2-(cyclopropylamino)-4-(naphth-2-yl)thiazol-3-ium bromide) toward the SK-MEL-5 melanoma cell line. Further antiproliferation investigations of 3c and 3e on the healthy, normal unaffected SK-MEL-5 cell line indicated their relative safety. Compound 3c showed an inhibition of eight isoforms of cyclin-dependent kinases (CDK); however, it exhibited the lowest IC₅₀ of 54.8 nM on CDK1 in comparison to Dinaciclib as a reference. Additionally, compound 3c revealed a remarkable downregulation of phospho-Tyr15 with a level (7.45 pg/mL) close to the reference. 3c mainly showed cell cycle arrest in the pre-G1 and G2/M phases upon analysis of the SK-MEL-5 cell line. The sequential caspase-3 assay for 3c indicated a remarkable overexpression level. Finally, a molecular docking study was adopted to elucidate the binding mode and interactions of the target compounds with CDK1.     

Solvation Rule for Solid‐Electrolyte Interphase Enabler in Lithium‐Metal Batteries

Despite the exceptionally high energy density of lithium metal anodes, the practical application of lithium‐metal batteries (LMBs) is still impeded by the instability of the interphase between the lithium metal and the electrolyte. To formulate a functional electrolyte system that can stabilize the lithium‐metal anode, the solvation behavior of the solvent molecules must be understood because the electrochemical properties of a solvent can be heavily influenced by its solvation status. We unambiguously demonstrated the solvation rule for the solid‐electrolyte interphase (SEI) enabler in an electrolyte system. In this study, fluoroethylene carbonate was used as the SEI enabler due to its ability to form a robust SEI on the lithium metal surface, allowing relatively stable LMB cycling. The results revealed that the solvation number of fluoroethylene carbonate must be ≥1 to ensure the formation of a stable SEI in which the sacrificial reduction of the SEI enabler subsequently leads to the stable cycling of LMBs.