Synthesis of ternary polypyrrole/Ag nanoparticle/graphene nanocomposites for symmetric supercapacitor devices

In this study, novel ternary synthesis of reduced graphene oxide (rGO) sheets via intercalation of Ag nanoparticles (Ag) and polypyrrole (PPy) was obtained for supercapacitor evaluations. The synthesis procedure of nanocomposite is simple, cheap, and ecologically friendly. The nanocomposites were analyzed by Fourier transform infrared-attenuated transmission reflectance (FTIR-ATR) and scanning electron microscopy-energy dispersion X-ray analysis (SEM-EDX). In addition, electrochemical performances of electrode active materials (rGO/Ag/PPy) of the samples were tested by means of galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The highest specific capacitance and energy density of rGO/Ag/PPy nanocomposite were obtained as C_sp = 1085.22 F/g and E = 36.92 Wh/kg for [rGO]_o/[Py]_o = 1/5 at 4 mV/s in 1 M H₂SO₄ solution. Under the optimized preparation conditions in different initial feed ratios ([rGO]_o/[Py]_o = 1/1, ½, 1/5, and 1/10) of rGO/Ag/PPy, nanocomposites acquired a high Coulombic efficiency, and a retention of 66% of its initial capacitance for [rGO]_o/[Py]_o = 1/10 after 1000 cycles. GCD and EIS measurements of rGO/Ag/PPy nanocomposite electrode active material allowed for supercapacitor applications.     

Carbazole derivative synthesis and their electropolymerization

This review article investigates the hot topics by presenting the latest advances in carbazole and its derivative synthesis and their electropolymerization processes. The carbazole-based compounds are particularly attractive due to their important photochemical and thermal stability and good hole-transport ability. Conjugated monomers of carbazole derivatives and their polymers attract interest due to their suitability in a broad range of applications, such as biosensors, corrosion inhibition, photovoltaics, electroluminescent devices, field-effect transistors and supercapacitors, etc. This review article divides two main parts. One of them includes effects of electropolymerization parameters of carbazole and chemical polymerization of carbazole derivatives. In addition, copolymers and composites of carbazole derivatives were presented in the first part. In the second part, the application of polycarbazole and its derivatives was examined as biosensors, corrosion inhibition, supercapacitor, battery, fuel cell, solar cell, electropolymerization, light emitting diodes, and OLEDs.     

Photon statistics of semiconductor microcavity lasers

We present measurements of first- and second-order coherence of quantum-dot micropillar lasers together with a semiconductor laser theory. Our results show a broad threshold region for the observed high-beta microcavities. The intensity jump is accompanied by both pronounced photon intensity fluctuations and strong coherence length changes. The investigations clearly visualize a smooth transition from spontaneous to predominantly stimulated emission which becomes harder to determine for high beta. In our theory, a microscopic approach is used to incorporate the semiconductor nature of quantum dots. The results are in agreement with the experimental intensity traces and the photon statistics measurements.     

Determination of glutathione disulfide levels in biological samples using thiol-disulfide exchanging agent, dithiothreitol

A reverse-phase HPLC method incorporating dithiothreitol (DTT) reduction for quantitative determination of oxidized glutathione (GSSG) in biological samples is described here. This method is based on our previous enzymatic reduction technique that uses N-1-(pyrenyl) maleimide (NPM) as a derivatizing agent. In our earlier method, glutathione disulfide (GSSG) was measured by first reducing it to GSH with glutathione reductase (GR) in the presence of NADPH. However, this is a very costly and time-consuming technique. The method described here employs a common and inexpensive thiol-disulfide exchanging agent, DTT, for reduction of GSSG to GSH, followed by derivatization with NPM. The calibration curves are linear over a concentration range of 25-1250 nm (r(2) > 0.995). The coefficients of variations for intra-run precision and inter-run precision range from 0.49 to 5.10% with an accuracy range of 1.78-6.15%. The percentage of relative recovery ranges from 97.3 to 103.2%. This new method provides a simple, efficient, and cost-effective way of determining glutathione disulfide levels with a 2.5 nm limit of detection per 5 microL injection volume.     

Copolymer formation of 9-(2-(benzyloxy)ethyl)-9H-carbazole and 1-tosyl-1H-pyrrole coated on glassy carbon electrode and electrochemical impedance spectroscopy

In this work, 9-(2-(benzyloxy)ethyl)-9H-carbazole (BzOCz) and 1-tosyl-1H-pyrrole (TsP) monomers were chemically synthesized and characterized by Fourier transform infrared reflectance (FTIR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. BzOCz and TsP were electrocoated on glassy carbon electrode (GCE) in various molar fractions (X _TsP?=?0.5, 0.83, 0.91, and 0.98) in 0.1?M sodium perchlorate/acetonitrile. The detailed characterization of poly(BzOCz-co-TsP) was studied by cyclic voltammetry, FTIR-attenuated total reflection spectroscopy and electrochemical impedance spectroscopy (EIS). The effects of different molar fractions during the preparation of modified electrodes were studied by EIS technique. The AC impedance technique was used to determine the capacitive behaviors of modified GCE via Nyquist, Bode magnitude, and Bode phase plots. The highest low frequency capacitance value was obtained as C _LF?=?23.94?μF?cm^?2 for X _TsP?=?0.98. Therefore, synthesized copolymer has more capacitive behavior than its homopolymers, such as C _LF?=?7.5?μF?cm^?2 for poly(BzOCz) and C _LF?=?9.44?μF?cm^?2 for poly(TsP). In order to interpret the AC impedance spectra, R(Q(RW)) electrical equivalent circuit was employed with linear Kramers–Kronig test. A mechanism for electropolymerization has been proposed for copolymer formation.     

Near-field light localization using subwavelength apertures incorporated with metamaterials

We report strong near-field electromagnetic localization by using subwavelength apertures and metamaterials that operate at microwave frequencies. We designed split ring resonators with distinct configurations in order to obtain extraordinary transmission results. Furthermore, we analyzed the field localization and focusing characteristics of the transmitted evanescent waves. The employed metamaterial configurations yielded an improvement on the transmission efficiency on the order of 27 dB and 50 dB for the deep subwavelength apertures. The metamaterial loaded apertures are considered as a total system that offered spot size conversion ratios as high as 7.12 and 9.11 for the corresponding metamaterial configurations. The proposed system is shown to intensify the electric fields of the source located in the near-field. It also narrows down the electromagnetic waves such that a full width at half maximum value of λ/29 is obtained.     

Seismic behaviour of isolated multi-span continuous bridge to nonstationary random seismic excitation

This paper concentrates on the results of responses of a multi-span continuous bridge isolated with double concave friction pendulum bearings subjected to non-stationary random seismic excitation characterized by the incoherence, the wave-passage, and the site-response effects. The earthquake excitation is modelled as a non-stationary random process as uniformly modulated broad-band excitation. To perform the seismic isolation procedure, the double concave friction pendulum bearings which are sliding devices that utilize two spherical concave surfaces are placed at each of the six support points of the deck. The non-stationary response of the isolated bridge is compared with the corresponding stationary response in order to study the effects of non-stationary characteristics of the earthquake input motion. Solutions obtained from the stationary and non-stationary stochastic analyses for the isolated bridge to spatially varying earthquake ground motions are compared for the special cases of the earthquake ground motion model. The spatially varying earthquake ground motions are described stochastically based on an empirical coherency loss function and a filtered power spectral density function. The site effect is considered by a transfer function derived from one dimensional wave propagation theory. It is observed that the stationary assumption is reasonable for the considered ground motion duration.     

Fluorimetric Determination of Thyroxine Hormone with Eu(III)-(Pyridine-2,6-Dicarboxylate) Tris Complex

We describe a method for the determination of thyroxine (Thy) using its quenching effect on Eu(PDA)₃ ^3- tris complex fluorescence. The relative fluorescence intensities are measured at fixed _exc = 282 nm, _em = 615 nm by titrating the metal complex with Thy in piperazine buffer solution at pH 6.5. Data indicated an associative type of reaction of two molecules valid between 0.0 < R < 1.0, R being the mole ratio of Eu(PDA)₃ ^3- to Thy. Over this ratio and up to (R 1.0) collisional quenching of Eu(PDA)₃ ^3- complex ion emission is seen as a result of heavy atom effect, intermolecular energy transfer playing the main role. This is also confirmed by the Stern-Volmer equation. In optimized experimental conditions, the L- form of Thy is determined in a range of 15.5–551.6 g/ml (2.0 × 10^–5 – 7.1 × 10^–4 M) with relative error of ±1.17%.     

Effective mass calculation for InSe, InSe:Er crystals

Undoped indium selenide (InSe) and Er doped InSe single crystals were grown by Bridgman–Stockberger method. The InSe crystals both undoped and doped Er had no cracks or voids on the surface. No polishing or cleaning treatments were carried out on the cleaved faces of these samples because of the natural mirror-like cleavage faces. The absorption measurements were carried out in the temperature range 10–320 K and the external electric field effect on the absorption measurements is investigated. The absorption edge shifted towards to the longer wavelengths under an electric field as 6 kV/cm. Using the electric field shifting, effective mass values are calculated.