NdFeO3 as a new electrocatalytic material for the electrochemical monitoring of dopamine

A new electrochemical sensor, based on NdFeO₃ nanoparticles as electrocatalytic material, was proposed here for the detection of dopamine (DA). NdFeO₃ nanoparticles were first synthesized by a simple thermal treatment method and subsequent annealing at high temperature (700 °C). The prepared electrocatalytic material has been characterized in detail by SEM-EDX, XRD, and Raman techniques. Characterization results display its sheet-like morphology, constituted by a porous network of very small orthorhombic NdFeO₃ nanoparticles. NdFeO₃ electrocatalytic material was then used to modify the working electrode of screen-printed carbon electrodes (SPCEs). Electrochemical tests demonstrated that NdFeO₃– modified screen-printed carbon electrode (NdFeO₃/SPCE) exhibited a remarkable enhancement of the dopamine electrooxidation, compared to the bare SPCE one. The analytical performance of the developed sensor has been evaluated for the detection of this analyte by means of the square-wave voltammetry (SWV) technique. The modified electrode showed two linear concentration ranges, from 0.5 to 100 μM and 150 to 400 μM, respectively, a limit of detection (LOD) of 0.27 μM (at S/N = 3), and good reproducibility, stability, and selectivity. Additionally, we also report an attempt made to propose the modified sensor for the simultaneous detection of dopamine and uric acid (UA). The procedure was also applied for the determination of dopamine in spiked real samples. So, this paper reports for the first time the use of a modified NdFeO₃ screen-printed electrode for developing an electrochemical sensor for the quantification of important biomolecules.

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Quantum Watermarking Using Entanglement Swapping

Digital watermarking is the process of embedding information into a digital signal in a way that is difficult to remove. In this article a secure quantum watermarking using entanglement swapping is proposed. Here the entanglement swapping is employed to build up a hidden layer of secure message under the conventional first layer of secure information sequence. In this protocol by insuring the security of transmission of the first layer of information sequence the security of the hidden secret messages is also proved to be reliable regardless of whether the hidden channel has been detected or not.     

Carbon nanotube-ionic liquid nanocomposite modified carbon-ceramic electrode for determination of dopamine in real samples

Room temperature 1-butyl-3-methylimidazolium tetraflouroborate ([BMIM][BF₄]) ionic liquid was employed for dispersion of multi walled carbon nanotubes (MWCNTs) and the formation of nanocomposite on the surface of a carbon-ceramic electrode. The surface of the modified electrode was characterized using scanning electron microscopy and electrochemical impedance spectroscopy. The modified electrode exhibited excellent electrochemical activity to oxidation of dopamine (DA); whereas electro oxidation of ascorbic acid (AA) was not seen and electro oxidation of uric acid (UA) appeared at a more positive potential than DA. The multi walled carbon nanotube-ionic liquid nanocomposite modified carbon-ceramic electrode was used for the selective determination of DA in the presence of high levels of AA and UA using differential pulse voltammetry. The calibration curve for DA was linear in the range of 3.00 to 130 µM with the detection limit (S/N=3) of 0.87 µM. The present electrode was successfully applied to the determination of DA in some commercial pharmaceutical samples and human blood serum.      

On existence and multiplicity of similarity solutions to a nonlinear differential equation arising in magnetohydrodynamic Falkner–Skan flow for decelerated flows

Previously, existence and uniqueness of a class of monotone similarity solutions for a nonlinear differential equation arising in magnetohydrodynamic Falkner–Skan flow were considered in the case of accelerating flows. It was shown that a solution satisfying certain monotonicity properties exists and is unique for the case of accelerated flows and some decelerated flows. In this paper, we show that solutions to the problem can exist for decelerated flows even when the monotonicity conditions do not hold. In particular, these types of solutions have nonmonotone second derivatives and are, hence, a distinct type of solution from those studied previously. By virtue of this result, the present paper demonstrates the existence of an important type of solution for decelerated flows. Importantly, we show that multiple solutions can exist for the case of strongly decelerated flows, and this occurs because of the fact that the solutions do not satisfy the aforementioned monotonicity requirements. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemical synthesis of tungsten-copper nanocomposite powder

In this study homogeneous powders of CuWO₄ and WO₃ was produced from ammonium para-tungstate (APT) and copper nitrate. Then, the product was used to prepare nano-sized W-Cu powder. Hence, a mixture of ammonium paratungstate and copper nitrate with predetermined weight proportion was made in distilled water, while the content of the beaker was being stirred at a certain speed to reach the desired composition of W-20 wt % Cu. Mixture was heated to 80–100°C for 6 h. Also, pH range was adjusted at about 3–4. The mixture was then evaporated and dried in the air. To reach W-Cu composite powder, the precursor powders burned out at 520°C for 2 h in the air to form W-Cu oxide powder and then were ball milled and reduced in H₂ atmosphere to convert it into W-Cu composite powder. The resulting powders were evaluated using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and differential thermal analysis techniques. The results showed that homogeneous powders of W-Cu with particle size of around 100 nm and a nearly spherical shape could be obtained by this process. Each particle include smaller parts with size of around 20–30 nm.     

Laser based fabrication of chitosan mediated silver nanoparticles

We report fabrication of silver nanoparticles (Ag NPs) by laser ablation technique in different concentrations of aqueous chitosan solution. The ablation process of silver plate was carried out by using a nanosecond Q-switched Nd:YAG pulsed laser and the characterization of Ag NPs was done by Transmission electron microscopy, UV-Vis spectroscopy, and X-ray diffraction. UV-visible plasmon absorption spectra revealed that the formation efficiency as well as the stability of nanoparticles was increased by addition of chitosan. On the other hand, the size decrement of nanoparticles was more remarkable in the higher chitosan concentration.     

C-terminal processing of yeast Spt7 occurs in the absence of functional SAGA complex

Background  

Spt7 is an integral component of the multi-subunit SAGA complex that is required for the expression of ~10% of yeast genes. Two forms of Spt7 have been identified, the second of which is truncated at its C-terminus and found in the SAGA-like (SLIK) complex.     

Mononitration of phenol derivatives by guanidinium nitrate and silica sulfuric acid under mild conditions

A mixture of guanidinium nitrate and silica sulfuric acid acts as mild and heterogeneous media for the efficient mono nitration of phenolic compounds in dichloromethane at room temperature.     

Confinement of halide ions within homologous inverse coordination hosts; modification of halide-ion selectivity

The structures of a series of spherical host-guest complexes [{MeE(PPh)(3)Li(4)·3thf}(4)(μ(4)-X)](-) (E = Al, [1X](-); E = Ga, [2X](-); E = In, [3X](-)) reveal that changing the halide ions (X = Cl, Br, or I) within their central tetrahedral Li(4) sites has negligible effect on the structural parameters.     

Removal of toxic hexavalent chromium by polyaniline modified clinoptilolite nanoparticles

In this work clinoptilolite nanoparticles were modified with conducting polyaniline by the polymerization of anilinium cations in and out side of the clinoptilolite channels and a nanocomposite of polyaniline/clinoptilolite was obtained. Cations (Na⁺, K⁺, Mg²⁺, Ca²⁺...) in the natural clinoptilolite structure were exchanged with anilinium cations by the treatment of clinoptilolite nanoparticles in an acidic solution of aniline monomer. The cation exchange process was confirmed by elemental analysis of nitrogen and carbon atoms of anilinium cations in clinoptilolite dry powder after treatment. The polyaniline/clinoptilolite nanocomposite was obtained by the oxidative polymerization of anilinium cations within the clinoptilolite structure. The polyaniline/clinoptilolite nanocomposite was characterized utilizing FT-IR and X-ray diffraction measurements and was used for the removal of Cr(VI) from aqueous solutions in chromate anion form as an important water pollutant. The effect of a number of parameters such as initial concentration of Cr(VI), amount of nanocomposite and contact time on the removal efficiency of Cr(VI) by polyaniline/clinoptilolite nanocomposite were determined and optimized. It was found that after 5 min of exposure of nanocomposite powder with Cr(VI) solutions in the concentration range of 25 to 100 ppm, more than 98% of chromate anions can be removed and the Cr(VI) removal capacity per one gram of nanocomposite is about 0.3 mmol of Cr(VI).