Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe3O4@polyaniline composites as a highly efficient,magnetically separable and atom‐economical catalyst for reduction of nitrobenzenes

The preparation of Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe₃O₄@polyaniline composites is reported. Fe₃O₄ nanoclusters were first synthesized through the solvothermal method and then the SiO₂ shell was coated on the Fe₃O₄ surface via a sol–gel process. To prepare Fe₃O₄@SiO₂@polyaniline composites, polyvinylpyrrolidone was first grafted on to the surface of Fe₃O₄@SiO₂ composites and subsequently polymerization of aniline was carried out via an ultrasound‐assisted in situ surface polymerization method. Selective etching of the middle SiO₂ layer was then accomplished to obtain the yolk–shell Fe₃O₄@polyaniline composites. The approach uses polyaniline (PANI) conductive polymer as a template for the synthesis of Ni@Pd core–shell nanoparticles. The catalytic activity of the synthesized yolk–shell Fe₃O₄@PANI/Ni@Pd composite was investigated in the reduction of o‐nitroaniline to benzenediamine by NaBH₄, which exhibited conversion of 99% in 3 min with a very low content of the catalyst. Transmission electron microscopy, X‐ray photoelectron spectroscopy, TGA, X‐ray diffraction, UV–visible, scanning electron microscopy, X‐ray energy dispersion spectroscopy and FT‐IR were employed to characterize the synthesized nanocatalyst. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermal Characteristics of PVA-PANI-ZnS Nanocomposite Film Synthesized by Gamma Irradiation Method

Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic(PA) setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.     

Physical–chemical hybrid transiency: A fully transient li‐ion battery based on insoluble active materials

Transient Li‐ion batteries based on polymeric constituents are presented, exhibiting a twofold increase in the potential and approximately three orders of magnitude faster transiency rate compared to other transient systems reported in the literature. The battery takes advantage of a close variation of the active materials used in conventional Li‐ion batteries and can achieve and maintain a potential of >2.5 V. All materials are deposited form polymer‐based emulsions and the transiency is achieved through a hybrid approach of redispersion of insoluble, and dissolution of soluble components in approximately 30 min. The presented proof of concept has paramount potentials in military and hardware security applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2021–2027     

Development of a new microelectrolysis system for in-situ electrodeposition of ultra-traces of gold prior to measurement by ETAAS

Electrodeposition is known to be suitable for separation and preconcentration of extremely low concentrations of analyte from bulk samples and is instrumentally is very simple. In this approach a new combined system was designed for in-situ electrodeposition of ultratrace levels of gold from micro samples on to a graphite furnace prior to determination by electrothermal atomic absorption spectrometry (ETAAS). Sediment samples were digested and traces of the gold content were extracted with boiling aqua regia. To prevent the highly corrosive effect of aqua regia media, the graphite tube surface was pre-coated by electrodeposition of ppm amounts of Pd prior to sample introduction. Separation of the analyte from the matrix was achieved by electrodeposition of the analyte in situ on the Pd/C surface of the furnace tube. Vanadium was also used as a modifier to stabilize the analyte from decomposition at charring temperatures. By using the proposed microelectrolysis preconcentration technique a considerable improvement in sensitivity and detection limit was achieved compared with conventional ETAAS. Characteristic masses for ED-ETAAS techniques in both nitric acid and aqua regia were reported to be m(o)=4.1 pg, with %RSD=2.9; the calculated LOD was 0.105 ppb, and typical calibration graphs for this element in nitric acid and aqua regia for both techniques were linear up to 70 microg L(-1) with about 99% recovery. Six reference sediments samples were tested by the proposed technique and by the Conv-ETAAS method. The results were in agreement with recommended values (reported by a reference laboratory using UV-visible spectrometry), demonstrating the efficiency of extraction and preconcentration of ultratrace levels of gold.     

Pd(II) anchored to modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles as a new magnetically recoverable catalyst for epoxidation of styrene

A new support for Pd(II) was synthesized via the functionalization of Fe₃O₄ nanoparticles with N-(2-aminoethyl)acetamide. PdCl₂ was anchored to the support for obtaining a heterogeneous magnetically recoverable catalyst for Pd(II). High yield and excellent selectivity were obtained for the green epoxidation of styrene derivatives using H₂O₂ as a green oxidant in H₂O as the solvent at 100 °C. Also, the recovered catalyst is applicable for four times without significant decrease in yield.     

Preparation,Characterization and Electrochemical Application of ZnS/ZnAl2S4 Nanocomposite for Voltammetric Determination of Methionine and Tryptophan Using Modified Carbon Paste Electrode

ZnS/ZnAl₂S₄ nanocomposite and 2‐chlorobenzoyl ferrocene, were synthesized and used to construct a modified carbon paste electrode. The electrooxidation of methionine at the surface of the modified electrode was studied. Under the optimized conditions, the square wave voltammetric (SWV) peak current of methionine increased linearly with methionine concentration in the range of 5.0×10^?8 to 8.0×10^?4 M and detection limit of 10.0 nM was obtained for methionine. The prepared modified electrode exhibits a very good resolution between the voltammetric peaks of methionine and tryptophan which makes it suitable for the detection of methionine in the presence of tryptophan in real samples.     

Development of effervescence-assisted switchable polarity solvent homogeneous liquid-phase microextraction for the determination of permethrin and deltamethrin in water samples prior to gas chromatography–flame ionization detection

An effervescent tablet-assisted switchable polarity solvent–based homogeneous liquid-phase microextraction combined with gas chromatography with flame ionization detection has been conducted for the separation, preconcentration, and detection of permethrin and deltamethrin in the river water specimens. Triethylamine (TEA) was utilized as the switchable polarity solvent in this method. The switching process was carried out by the dissolution of an effervescent tablet including an effervescency agent (sodium carbonate) and a proton donor agent (citric acid). Changing the pH of the specimen solution enhanced the conversion of TEA into protonated triethylamine carbonate through the tablet that generated carbon dioxide bubbles in situ. Finally, the addition of sodium hydroxide changed the ionization state of TEA and separated the two phases. Influential factors in the extraction were investigated. According to optimal situations, the limit of detection and the limit of quantification were 0.16 and 0.5 μg L⁻¹ for permethrin and 0.03 and 0.1 μg L⁻¹ for deltamethrin, respectively. The preconcentration factor was 194 in river water samples and inter- and intra-day precision (relative standard deviation %; n = 5) was <5%. The extraction recovery was obtained in the range of 93.0%–97% for permethrin and deltamethrin in water samples.     

A Pseudospectral Method for Fractional Optimal Control Problems

In this article, a direct pseudospectral method based on Lagrange interpolating functions with fractional power terms is used to solve the fractional optimal control problem. As most applied fractional problems have solutions in terms of the fractional power, using appropriate characteristic nodal-based functions with suitable power leads to a more accurate pseudospectral approximation of the solution. The Lagrange interpolating functions and their fractional derivatives belong to the Müntz space; such functions are employed to show that a relationship exists between the Karush–Kukn–Tucker conditions associated with nonlinear programming and the first optimal necessary conditions. Furthermore, the convergence of the method is investigated. The obtained numerical results are an indication of the behavior of the algorithm.