Unexpected regio- and stereoselective [4 + 3] cycloaddition reaction of azomethine ylides with benzylidene thiazolidinediones: synthesis of pharmacologically active spiroindoline oxazepine derivatives and theoretical study

Molecular Diversity - An unexpected regio- and stereoselective [4?+?3] cycloaddition reaction of azomethine ylides with 5-benzylidenethiazolidine-2,4-diones has been successfully...     

A Novel Bacterial Route to Synthesize Cu Nanoparticles and Their Antibacterial Activity

Journal of Cluster Science - This report focuses on a facile and one-pot way to synthesize stable Cu nanoparticles (NPs) through a bacterial approach using an inexpensive and non-toxic copper salt...     

Morphology of polyaniline nanofibers synthesized under different conditions

Polyaniline nanofibers are readily synthesized by bulk polymerization; ammonium per sulphate (APS) is used as oxidizing agent and hydrochloric acid as dopant without any hard or soft templates. A detailed study was conducted on the effect of a variety of synthetic conditions on the size and morphology of the polyaniline nanostructure. These conditions include the concentration of dopant, and the APS-to-aniline and acid-to-aniline molar ratios. The morphology of the nanofibers was confirmed by SEM and TEM. XRD and FT-IR and UV–visible spectroscopy were used for structural characterization of nanofibers. The results showed that not only the microstructure of the polyaniline product, but also other characteristics, for example conductivity, crystallinity, and, more importantly, the efficiency of the process are strongly affected by the synthetic conditions.     

Slant Submanifolds of Almost Contact Metric 3-Structure Manifolds

In this paper we introduce the notion of slant submanifold of an almost contact metric 3-structure manifold. We give some examples and characterize these submanifolds. Moreover, Sasakian slant submanifolds of an almost contact 3-structure manifold are defined and studied. We also establish a sharp inequality including the squared mean curvature and Ricci curvature of a Sasakian slant submanifold.     

Circular ripple formation on the silicon wafer surface after interaction with linearly polarized femtosecond laser pulses in air and water environments

Ultrashort laser pulse interaction with the surface of silicon wafer in air and water environments is investigated. Ti:sapphire laser with 40 femtosecond laser pulses at 790 nm and 10 Hz repetition rate was used. The ablation threshold of the silicon surface in the air was determined to be about 0.28 J cm^?2. The surface morphology was studied by using scanning electron microscope images. The size of the regular ripples formed in the air environment is a little smaller than the laser wavelength. Due to the nonlinear interaction and self-focusing before the target, the ripples size reduced to nearly a half of the laser wavelength in the water. Moreover, the spikes’ structure formation and their diameter in air and water were studied. Two regimes for spike formation in water are proposed that can explain the anomalous decrease of the spikes’ diameter in higher fluence. During the interaction of single linearly polarized femtosecond laser pulse with the surface, an irregular ripple formation that called circular ripple is observed. This structure which is a result of radiation pressure implies to the surface by the end of the pulse. A new physical model for interpretation of the circular ripples formation based on the ponderomotive force of an ultrashort pulse laser is proposed which can predict the size of the circular ripples. The calculated results are in accordance with our experimental findings.     

EIS and adjunct electrical modeling for material selection by evaluating two mild steels for use in super-alkaline mineral processing

The production of metal concentrates during mineral processing of ferrous and non-ferrous metals involves a variety of highly corrosive chemicals which deteriorate common mild steel as the material of choice in the construction of such lines, through rapid propagation of localized pitting in susceptible parts, often in sensitive areas. This requires unscheduled maintenance and plant shut down. In order to test the corrosion resistance of different available materials as replacement materials, polarization and electrochemical impedance spectroscopy (EIS) tests were carried out. The EIS numerical outputs were then transformed into an equivalent electric circuit using Z-View software, and the predictive behavior was contrasted with actual performance after long-term immersion, depicted through SEM, EDS, XRD and weight change observations. Also, results of pits and cracks, obtained with climax software-enhanced polarization resistance, and reduced capacitance added to much diminished current densities, verified the acceptable performance of CK₄₅ compared with high priced stainless steel substitutes with comparable operational life. Therefore, CK₄₅ can be a suitable alternative in steel constructions which are exposed to super-alkaline and corrosive environments.     

Thiozonation and thiozonolysis of triatomic sulfur (S<Subscript>3</Subscript>) on the C<Subscript>70</Subscript> fullerene: a DFT study

Density functional theory calculations have been carried out to investigate the [2?+?x] x?=?1, 2, and 3 cycloaddition reactions (paths A, B, and C) of triatomic sulfur (S₃) with the C₇₀ fullerene in terms of geometry, energies, and electronic structures. The thiozonation (S₃) on the hexagon–hexagon and hexagon–pentagon bonds of the C₇₀ fullerene through 1,3-dipolar reaction, i.e., [2?+?3] cycloaddition, is generally exothermic, while through the chelotrope additions, i.e., [2?+?1] cycloaddition, are endothermic. The results indicate that the 1,3-dipolar cycloaddition is the most preferable path. Having more negative values of reaction energies E_r together with the lower barrier heights, thiozonation of the hexagon–hexagon bonds is thermodynamically and kinetically more favorable than hexagon–pentagon ones. Moreover, the addition of thiozone to the hexagon–hexagon bonds near the pole area of the C₇₀ leads to more negative reaction energies. Therefore, it is established that the arrangement and position of C=C bonds play an important role in the thiozonation of C₇₀ fullerene. Thiozonolysis of triatomic sulfur (S₃) indicates that S–S bond cleavage has not occurred, instead a sulfur bridge over a C–C bond or a four-membered ring of 1,2-dithietane-1-sulfide is preferred to be formed.     

Reaction of barbituric/thiobarbituric acid with phosphines or phosphites and dialkyl acetylenedicarboxylates for synthesis of phosphorus zwitterions or phosphonate derivatives

Abstract

A three-component reaction between barbituric/thiobarbituric acid, phosphines, and dialkyl acetylenedicarboxylates in dry acetonitrile led to the formation of barbiturate/thiobarbiturate-functionalized stable zwitterionic salts in a one-pot process. When trialkyl phosphites were used instead of phosphines, barbiturate/thiobarbiturate-functionalized phosphonates were obtained in good yields.     

Exploring the electronic and magnetic properties of zigzag and armchair BC2N nanotubes: a DFT study

A density functional study is performed to investigate the electronic and magnetic properties of zigzag and armchair BC₂N nanotubes based on the ¹³C, ¹⁵N, and ¹¹B NMR parameters and natural charge analysis. We considered three types of zigzag nanotubes, ZZ-1, ZZ-2, and ZZ-3 (n, 0) with n = 3, 4, and 5, as well as two types of armchair nanotubes: AC-1 and AC-2 (n, n) with n = 3 and 4. The obtained results indicate the divisions of the electrostatic environments around C nuclei into a few layers, consistent with the calculated natural charges on C atoms. A good correlation is seen between the layers of chemical shielding isotropy as well as anisotropy, σ _iso, and Δσ, and the five local structures around carbon atoms. Successive BN units lead to larger ¹⁵N σ _iso values (96.5–105.5 ppm) in comparison with the individual BN units (74.3–92.0 ppm in the ZZ-2(n, 0) and 47.4–61.7 ppm in the ZZ-3(n, 0)). Slight differences in the values of ¹¹B σ _iso clarify diminutive diversity in the electron densities of boron nuclei, while Δσ values indicate the more apparent range of changes.     

Green Synthesis of Ag Nanoparticles by Callicarpa Maingayi: Characterization and Its Application with Graphene Oxide for Enzymeless Hydrogen Peroxide Detection

A facile green synthesis of silver nanoparticles (AgNPs) was achieved using aqueous leaf extract of Callicarpa Maingayi as a reducing and stabilizing agent during the synthesis from its salt solutions. The synthesized silver nanoparticles were analyzed with transmission electron microscopy (TEM), X‐ray diffraction (XRD) and energy dispersive spectrometer (EDS). XRD study shows that the particles are crystalline in nature with face centered cubic geometry. The crystallite size obtained from XRD is about 15 nm which is in agreement well with the TEM results. A new nanostructure sensor was constructed by immobilizing silver nanoparticles and graphene oxide (AgNPs‐GO) composite film on a glassy carbon electrode (AgNPs‐GO/GCE). It was found that the AgNPs‐GO composite exhibits good catalytic activity toward the reduction of hydrogen peroxide (H₂O₂), leading to an enzymeless sensor with a fast amperometric response time of less than 5 s, high selectivity, good reproducibility and stability. The linear range was 5.0 μM to 700 μM with a detection limit of 0.6 μM (S/N = 3).