An alkylzinc bromide and a lithium alkyldibromozincate containing tris(organosilyl)methyl groups

The lithium reagent (3) reacts with a molar equivalent of anhydrous zinc bromide to give the dimeric compound (2a), in which zinc is four-coordinate. The product from a similar reaction with Li{C(SiMe₃)₂(SiMe₂NPhMe)} is the lithium zincate [Li(THF)₂(μ-Br)₂Zn{C(SiMe₃)₂(SiMe₂NPhMe)}] (4), in which the zinc is only three-coordinate. The crystal structures of 2a and 4 have been determined.     

Energy band engineering of flexible gallium arsenide through substrate cracking with pre‐tensioned films

Flexible electronics based on the otherwise rigid conventional crystalline semiconductors is emerging as a new class of technology. However, the existing layer‐transfer approaches for implementing such technologies is mostly focused on maintaining the performance of the original device. Here we show that layer transfer through substrate cracking with a pre‐tensioned nickel film readily enables the manipulation of the electronic band structure in flexible gallium arsenide (GaAs) devices. We empirically and theoretically quantify the effect of ‘engineered' residual strain on the electronic band structure in these flexible GaAs devices. Photoluminescence and quantum efficiency measurements indicate the widening of the GaAs energy bandgap due to the residual compressive strain. The experimental results are in good agreement with our theoretical calculations. This study introduces a new way for strain engineering in flexible compound semiconductors with important implications for electronic and optoelectronic applications. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Synthesis,spectroscopic investigations,and computational study of 4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde

4-((9,10-dioxo-9,10-dihydroanthracen-1-yl)oxy)-3-methoxybenzaldehyde has been synthesized in an attempt to obtain a new photochromic compound. The optimized molecular structure, mole fractions of title compound in trans and ana forms have been investigated. UV-visible spectra of the compound were also recorded. Upon irradiation with 300 nm light, the camel solid turned orange, in which a visible absorption band was observed at 475 nm. The electronic properties, such as HOMO, LUMO and band gap energies were obtained by the time-dependent DFT (TD-DFT) approach. The predicted nonlinear optical properties of the title compound are much greater than those of urea. Transition structures were calculated by QST3 and IRC methods which yielded the potential energy surface and activation energy.     

Sonochemical Synthesis of Spherical Silica Nanoparticles and Polymeric Nanocomposites

In this work spherical SiO₂ nanoparticles were synthesized by sonochemical method using a new Schiff-base as a capping agent. The silica nanoparticles were obtained by hydrolysis of tetraethyl orthosilicate in aqueous alcohol solution. The effect of different parameters such as molar concentration of Schiff-base ligands and ultrasonic irradiation on the morphology and size of the products was examined. The results demonstrated that applying the appropriate amount of Schiff-base could be effective in control of particle size. The influence of SiO₂ nanostructures on the flame retardancy of the poly styrene, poly vinyl alcohol, cellulose acetate and ethyl cellulose was studied. In-situ and ex situ nanocomposites were investigated and results confirm that flame retardancy of in situ nanocomposites were better than ex situ samples. HO···Si–O–Si···OH barrier prevents reaching of flame, heat and oxygen to the polymeric nanocomposites.     

SBA-15/Metformin as a novel sorbent combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) for highly sensitive determination of Pb,Cd and Ni in food and environmental samples

This paper established a new, rapid and sensitive method for the ultra-trace determination of lead, cadmium and nickel in food and environmental samples preconcentrated by dispersive solid-phase extraction (DSPE) combined with surfactant-assisted dispersive liquid–liquid microextraction (SA-DLLME) prior to graphite furnace atomic absorption spectrometry. SBA-15/Met was synthesized and used as a new efficient sorbent for the extraction of metal ions in DSPE. It was characterized by TEM and TGA techniques. After DSPE step, stripped metal elements were complexed with dithizone, and then, the complexes were extracted into carbon tetrachloride by using SA-DLLME. A conventional nonionic surfactant, triton X-100 was used as a disperser agent. Under the optimized conditions, the limit of quantifications was found to be 2.5 ng L^?1 for Pb²⁺, Cd²⁺ and 5.0 ng L^?1 for Ni²⁺. The limits of detection were 1.5 ng L^?1 for Ni²⁺ and 0.75 ng L^?1 for Pb²⁺ and Cd²⁺, with enrichment factor of 1650. The optimized method exhibited a good precision level with relative standard deviations (RSDs%) values of 4.9, 5.2 and 5.0% for 1 μg L^?1 Pb²⁺, Cd²⁺ and Ni²⁺, respectively (n = 7). Application of the proposed method to the analysis of fish-certified reference material produced results that were in good agreement with the certified values.     

Sulfuric acid heterogenized on magnetic Fe3O4 nanoparticles: A new and efficient magnetically reusable catalyst for condensation reactions

Immobilized sulfuric acid on magnetic Fe₃O₄ nanoparticles (Fe₃O₄ MNPs‐OSO₃H) as a new solid acid nanocomposite was successfully synthesized and its catalytic activity in a series of condensation reactions was studied. High catalytic activity, simple separation from reaction mixture by an external magnet and good reusability are several eco‐friendly advantages of this catalytic system. It is noteworthy that this catalytic system is applicable to a wide range of spectrum of aromatic aldehydes, and the desired products were obtained in good to excellent yields under mild conditions. The use of ecofriendly solvents makes also this synthetic protocol ideal and fascinating from the environmental point of view.     

Amino acid ionic liquid‐based titanomagnetite nanoparticles: An efficient and green nanocatalyst for the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazoles

The amino acid ionic liquid tetrabutylammonium asparaginate (TBAAsp) was immobilized on titanomagnetite (Fe_3?xTi_xO₄) nanoparticles in a facile one‐pot process using an organosilane compound (TMSP) as spacer. The modified Fe_3?xTi_xO₄@TMSP@TBAAsp magnetic nanoparticles were characterized using Fourier transform spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry and thermogravimetric analysis. The resulting analytical data clearly verified the successful immobilization of the ionic liquid on the magnetic substrate. The magnetic ionic liquid‐based nanoparticles exhibited high catalytic activity in the synthesis of 1,4‐dihydropyrano[2,3‐c]pyrazole derivatives via a one‐pot three‐component reaction under mild reaction conditions. The catalyst was easily recycled and reused for at least six runs without any considerable loss of activity.