Controlled synthesis of ZnO nanoparticles from a Zn(II) coordination polymer: Structural characterization,optical properties and photocatalytic activity

A zinc coordination polymer derived from pyridine-2,6-dicarboxylate (PDC), {[Zn₂(PDC)₂]}_n, was successfully prepared via conventional, sonication and microwave-irradiation methods. The composition and characteristics of the obtained coordination polymers (CPs) were investigated by elemental analysis, TGA/DTA, X-ray diffraction and spectroscopic techniques. The so obtained CPs were heat-treated in the air at 600 °C for 2 h to produce ZnO of nanosized particles (NPs). It is of interest to note that the synthesis approach of the precursor greatly affects both the nanoparticle size and the structure of the resulting ZnO NPs. Moreover, the smallest particle size was associated with the sample derived from the ultrasonically prepared precursor. TEM analysis revealed that all samples have sphere-like morphologies. Structural analysis of the prepared ZnO samples was conducted and compared using Rietveld analysis of their PXRD patterns. Optical band gap calculations based on analysis of the UV–vis spectra of ZnO samples using Tauc's power law were achieved. The highest band gap of 3.63 eV was observed for ZnO sample obtained from the ultrasonically prepared precursor. Furthermore, the photocatalytic activity of ZnO NPs for the removal of Eosin Y color was monitored. The highest removal efficiency was recorded for ZnO originated from the ultrasonically synthesized precursor. Enhancement of removal efficiency that reached 98% was attained in only a period of 8 min. Its recycling test showed that it can be reused without structural changes over four cycling experiments.     

Optimization of extraction and quantification technique for phenolics content of garlic (Allium sativum): An application for comparative phytochemical evaluation based on cultivar origin

A range of conventional, i.e. maceration, percolation, ultrasonic assisted, Soxhlet and Soxtec extraction (STE), to advanced extraction techniques of accelerated solvent extraction (ASE) was utilized for the first time in order to optimize the extract yield and recovery of phenolics—gallic acid (GA), rutin (RT) and quercetin (QT)—quantified via ultra-high performance liquid chromatography with diode array detector (UHPLC–DAD). The effect of solvents (n-hexane, dichloromethane and methanol) and temperature (60, 80 and 100°C) upon extraction yield, phenolic content and antioxidant activity (DPPH, ABTS and DPPH) was studied, and the method was validated in commercial food samples from Saudi Arabia, China and India. A high extract yield with percentage recovery was observed for STE (1221.10 mg/5 g; 24.42%) and ASE techniques (91.50 mg/1 g; 9.15%) in methanol at 100°C. UHPLC–DAD showed retention times (min) of 0.67, 1.93 and 1.90 for GA, RT and QT, respectively in the shortest runtime of 3 min. The yield for phenolics was higher for STE/ASE (ppm): 15.27/15.29 (GA), 85.24/37.56 (RT) and 52.20/33.40 (QT), respectively. In terms of antioxidant activities, low IC₅₀ values (μg/ml) of 1.09/1.18 (DPPH), 2.11/5.32 (ABTS) and 4.35/7.88 (phenazine methosulfate–nicotinamide adenine dinucleotide) were observed for STE and ASE, respectively. Multivariate analysis for STE showed a significant (P = 0.000) correlation for extraction type vs. extract yield and phenolics content; however, there was no significance for antioxidant activities vs. extraction type. ASE showed a positive correlation for solvent vs. extraction yield, phenolics and antioxidant activity; however, there was no correlation for extraction yield and DPPH activity. Principal component analysis for STE showed a major variability (52.02%) for extraction yield and phenolics in PC1 followed by PC2 (38.30%) for antioxidant activities. For ASE, PC1 (48.68%) showed a positive correlation for solvent vs. extraction yield and phenolics while PC2 (33.12%) showed a positive correlation for temperature and antioxidant activities. STE and ASE were the optimized extraction techniques for the garlic food sample while a significant effect of solvent and temperature was observed upon extraction yield, phenolics and antioxidant activity.     

Structural,magnetic and optical properties of two concomitant molecular crystals

A new 1D complex has been prepared and characterized. X-ray single crystal structure confirms that the Cu(II) ions assemble in alternating chains with Cu … Cu distances of 2.5685(4) and 3.1760(4) Å. The temperature dependence of the magnetic susceptibility reveals an antiferromagnetic interaction between the paddle-wheel copper centers with an exchange of −300 cm⁻¹. The exchange integral was also determined by quantum chemical ab-initio calculations, using polarised and unpolarised basis sets reproducing well the experimental value. The second harmonic generation efficiency of a concomitantly crystallized material was evaluated and was found to be comparable to urea.     

Peroxide Coordination of Tellurium in Aqueous Solutions

Tellurium–peroxo complexes in aqueous solutions have never been reported. In this work, ammonium peroxotellurates (NH₄)₄Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂ ( 1 ) and (NH₄)₅Te₂(μ‐OO)₂(μ‐O)O₅(OH)?1.28 H₂O?0.72 H₂O₂ ( 2 ) were isolated from 5 % hydrogen peroxide aqueous solutions of ammonium tellurate and characterized by single‐crystal and powder X‐ray diffraction analysis, by Raman spectroscopy and thermal analysis. The crystal structure of 1 comprises ammonium cations and a symmetric binuclear peroxotellurate anion [Te₂(μ‐OO)₂(μ‐O)O₄(OH)₂]^4?. The structure of 2 consists of an unsymmetrical [Te₂(μ‐OO)₂(μ‐O)O₅(OH)]^5? anion, ammonium cations, hydrogen peroxide, and water. Peroxotellurate anions in both 1 and 2 contain a binuclear Te₂(μ‐OO)₂(μ‐O) fragment with one μ‐oxo‐ and two μ‐peroxo bridging groups. ¹²⁵Te NMR spectroscopic analysis shows that the peroxo bridged bitellurate anions are the dominant species in solution, with 3–40 %wt H₂O₂ and for pH values above 9. DFT calculations of the peroxotellurate anion confirm its higher thermodynamic stability compared with those of the oxotellurate analogues. This is the first direct evidence for tellurium–peroxide coordination in any aqueous system and the first report of inorganic tellurium–peroxo complexes. General features common to all reported p‐block element peroxides could be discerned by the characterization of aqueous and crystalline peroxotellurates.     

Response surface methodology toward the optimization of high-energy carotenoid extraction from Aristeus antennatus shrimp

High-energy assisted extraction techniques, like ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), are widely applied over the last years for the recovery of bioactive compounds such as carotenoids, antioxidants and phenols from foods, animals and herbal natural sources. Especially for the case of xanthophylls, the main carotenoid group of crustaceans, they can be extracted in a rapid and quantitative way with the use of UAE and MAE.     

Hellmann–Feynman connection for the relative Fisher information

The (i) reciprocity relations for the relative Fisher information (RFI, hereafter) and (ii) a generalized RFI–Euler theorem are self-consistently derived from the Hellmann–Feynman theorem. These new reciprocity relations generalize the RFI–Euler theorem and constitute the basis for building up a mathematical Legendre transform structure (LTS, hereafter), akin to that of thermodynamics, that underlies the RFI scenario. This demonstrates the possibility of translating the entire mathematical structure of thermodynamics into a RFI-based theoretical framework. Virial theorems play a prominent role in this endeavor, as a Schrödinger-like equation can be associated to the RFI. Lagrange multipliers are determined invoking the RFI–LTS link and the quantum mechanical virial theorem. An appropriate ansatz allows for the inference of probability density functions (pdf’s, hereafter) and energy-eigenvalues of the above mentioned Schrödinger-like equation. The energy-eigenvalues obtained here via inference are benchmarked against established theoretical and numerical results. A principled theoretical basis to reconstruct the RFI-framework from the FIM framework is established. Numerical examples for exemplary cases are provided.     

Gutmann's Donor Numbers Correctly Assess the Effect of the Solvent on the Kinetics of SNAr Reactions in Ionic Liquids

We report an experimental study on the effect of solvents on the model S_NAr reaction between 1‐chloro‐2,4‐dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf₂^?, DCN^?, SCN^?, CF₃SO₃^?, PF₆^?, and FAP^? with the series of cations 1‐butyl‐3‐methyl‐imidazolium ([BMIM]⁺), 1‐ethyl‐3‐methyl‐imidazolium ([EMIM]⁺), 1‐butyl‐2,3‐dimethyl‐imidazolium ([BM₂IM]⁺), and 1‐butyl‐1‐methyl‐pyrrolidinium ([BMPyr]⁺). The observed solvent effects can be attributed to an “anion effect”. The anion effect appears related to the anion size (polarizability) and their hydrogen‐bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.     

Synthesis and characterization of copper(II) Schiff base complex supported on Fe3O4 magnetic nanoparticles: a recyclable catalyst for the one‐pot synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones

Fe₃O₄–Schiff base of Cu(II) is found to be a recyclable and heterogeneous catalyst for the rapid and efficient synthesis of various 2,3‐dihydroquinazolin‐4(1H)‐one derivatives from the two‐component condensation of 2‐aminobenzamide and an aldehyde. This reaction is simple, green and cost‐effective. Separation and recycling can also be easily done by magnetic decantation of the Fe₃O₄ nanoparticles with an external magnet. The prepared catalyst was characterized using thermogravimetry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, inductively coupled plasma analysis, X‐ray diffraction and scanning electron microscopy. Copyright © 2015 John Wiley & Sons, Ltd.     

On Coron's problem for the p-Laplacian

We prove that the critical problem for the p-Laplacian operator admits a nontrivial solution in annular shaped domains with sufficiently small inner hole. This extends Coron's result [4] to a class of quasilinear problems.