Electrocatalytic Investigations of Cu(II) and Fe(III) Complexes of Salophen Derivative Schiff Bases on the Pencil Graphite Electrode

This present study describes a pencil graphite electrode surface covered with Cu(II) and Fe(III) complexes based on Salophen derivative Schiff bases in acetonitrile solution containing LiClO₄ as a supporting electrolyte. Cyclic voltammetry method was used for the surface modification procedure with 25 cycle at a sweep rate of 50 mV s^?1. Some characterization methods were used to identify of the prepared modified surfaces including cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Ultraviolet‐visible Spectroscopy (UV‐Vis), and Scanning Electron Microscopy/Energy Dispersive X‐ray Spectroscopy (SEM/SEM‐EDX). The catalytic activity of these modified surfaces on the electrochemical oxidation of catechol (CC) was investigated and they compared with each other. The results demonstrated that these modified electrodes showed perfect electrocatalytic activity on the catechol determination, however the modified electrode prepared with the Cu(II) complex has higher catalytic activity than this prepared with the Fe(III) complex thanks to its the lower detection limit.     

Design and characterization of Bodipy derivatives for bulk heterojunction solar cells

Two electron rich Bodipy dyes with strong absorptivities in the visible region were designed and synthesized as potential electron donors in bulk heterojunction photovoltaic constructs. Overall efficiency is above 1%, with impressive responsiveness at both UV and near-IR ends of the visible spectrum. Computational studies reveal an unexpected effect of meso-substituents on the electron transfer efficiency.     

Evaluation of poly(4‐methyl‐1‐pentene) as a dielectric capacitor film for high‐temperature energy storage applications

Poly(4‐methyl‐1‐pentene) (P4MP) was characterized to evaluate its viability as a high‐temperature dielectric film for capacitors. Detailed investigation of thermal, mechanical, rheological, and dielectric properties was carried out to assess its high‐temperature performance and processability. P4MP was melt‐processable below 270 °C without degradation and application temperatures as high as 160–190 °C can be achieved. The dielectric constant and loss of melt‐processed P4MP films was comparable to biaxially oriented polypropylene (BOPP) capacitor films, although the dielectric strength was lower. Enhancements in dielectric strength up to 250–300% were achieved via solution‐processing P4MP films, which could be easily scaled up on a roll‐to‐roll platform to yield isotropic, free‐standing films as thin as 3–5 μm. The influence of crystal structure, crystallinity, and surface morphology of these films on the dielectric properties was examined. The dielectric strength was further increased by 450% through biaxial stretching of solution‐cast films, and a Weibull breakdown field of 514 V/μm was obtained. The dielectric constant was very stable as a function of frequency and temperature and the dielectric loss was restricted to <1–2%. Overall, these results suggest that BOP4MP is a promising candidate to obtain similar energy density as a BOPP capacitor film but at much higher operating temperatures. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1497–1515     

Intrinsic photoluminescence properties of amorphous Si3B3N7 ceramic

Amorphous Si₃B₃N₇ ceramic shows intrinsic photoluminescence. Three distinctive emission regions have been observed. Excitation with wavelengths between 254 and 330 nm stimulates intense blue emissions with peak maxima ranging from 447 to 479 nm. Exciting between 315 and 420 nm results in two broad emission peaks; the first in the range between 400 and 440 nm, and the second between 560 and 690 nm. Of these two latter emissions, the one in the violet region dominates in intensity over the other one in the red region, thus a violet color is perceived with the eye via excitation with 330 nm or higher wavelengths. The three distinct intrinsic emissions in the photoluminescence spectrum of amorphous Si₃B₃N₇ ceramic are related to defect centers in three topologically different regions in its structure. Dependence of emission on excitation wavelength is associated with the Red-Edge Effect and can be explained with a reabsorption mechanism at the red excitation edge.     

Beta-transition properties for neutron-rich Sn and Te isotopes by Pyatov method

Based on Pyatov’s method, the low-lying Gamow-Teller (GT) 1⁺ state energies and log(ft) values for ^128,130,132Sb and ^132,134,136I isotopes have been calculated. In this method, the strength parameter of the effective spin-isospin interaction is found by providing the commutativity of the GT operator with the central part of the nuclear Hamiltonian. The problem has been solved within the framework of RPA. The calculation results have been compared with the corresponding experimental data.      

Synthesis and GIAO NMR calculations for some new 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives: comparison of theoretical and experimental 1H and 13C chemical shifts

Four novel 3-alkyl(aryl)-4-(4-methoxycarbonylbenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (2) were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) with methyl 4-formylbenzoate and characterized by elemental analyses and IR, 1H NMR, 13C NMR and UV spectral data. In addition, isotropic 1H and 13C nuclear magnetic shielding constants of 2 were obtained by the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level. The geometry of each compound was optimized using the 6-311G basis set.     

Surface structure and photoluminescence properties of AZO thin films on polymer substrates

Al‐doped zinc oxide (AZO) thin films were deposited on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering method at room temperature. The effects of film thickness on the surface structure and the photoluminescence properties of the films were investigated by atomic force microscopy (AFM), secondary ion mass spectroscopy (SIMS) and room temperature photoluminescence (PL). AFM analysis showed that the surface of all films was extremely flat and uniform at nanoscale. Root mean square (RMS) value of the surface roughness which scanned the surface area of 3 µm by 3 µm and grain size increased with increasing the film thickness. Thus, the surface morphology of the films became rough because of the coarse grains. The depth profile of AZO layers was analyzed by SIMS. It was found that the thickness of the AZO layer is almost same with the desired film thickness. The PL intensity of the dominant peak decreased and shifted slightly towards the shorter wavelengths with increasing the film thickness. According to the relationships between luminescence intensity and crystalline characteristics, it was observed that the intensity of the peak decreased by the increased surface area of the grains. Copyright © 2014 John Wiley & Sons, Ltd.     

The effect of natural rubber crosslink density on real time birefringence,true stress and true strain behavior

A newly developed real time spectral birefringence technique was implemented to follow the coupled relationships between birefringence, true stress and true strain behavior of varying crosslink density natural rubber vulcanizates at room temperature. It was shown that the stress optical law is valid even at early stages of crystallization during stretching and there exists a critical birefringence beyond which the metastable “near perfect” oriented and highly distorted crystalline regions form and upon retraction this crystalline order disappears at the same critical birefringence level. These crystalline regions exhibit nematic order with significant axial registry distortions at early stages of the formation. They are suggested to form at or near the juncture points of the chemical network formed by crosslinks, and physical network by chain entanglements where the orientability of the chains is the most efficient.     

Structural analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes

Structure of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes has been analyzed through wide-angle X-ray diffraction (WAXD), density, infrared dichroism, and birefringence measurements. There are three different types of crystalline structure in these fibers: two of these are the two types of orthorhombic with different orientation modes (the ordinary c-axis orientation (c//Z), and the preferential orientation of c-axis to the direction perpendicular to the fiber axis (c⟂Z)); and the third is pseudohexagonal. The weight fractions of the three types of crystals and amorphous phase were analyzed combining the WAXD integrated intensity and density data. The relation between crystalline orientation factors obtained separately from the WAXD measurement and the infrared dichroic ratio is also discussed. The birefringence of these fibers shows negative and positive values, depending on drawing and annealing temperatures. Considering the intrinsic birefringence and weight fraction of the c//Z, c⟂Z, and pseudohexagonal crystals, birefringence of the amorphous phase was evaluated. The amorphous birefringence shows positive values and decreases with an increase in the annealing temperature. From the analyzed fiber structure, it was speculated that the c⟂Z and pseudohexagonal crystals are preferentially formed in the drawing process irrespective of the drawing temperature.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2471–2482, 1998