Synthesis and Crystal Structure of μ-oxo-bis[(octaethyloxoporphinato)iron(III)] Tetrafluoroborate

Exposure of dichloromethane solution of [OEOPFe(BF₄)], where OEOP is the monoanion of octaethyloxoporphyrin, to dioxygen results in its transformation into the μ-oxo bridged compound, [(OEOPFe)₂O)](BF₄)₂. The molecular structure of the title compound, [(OEOPFe)₂O](BF₄)₂, was determined by single-crystal X-ray diffraction. It contains a binuclear centrosymmetric [(OEOPFe)₂O]²⁺ cation (the bridging O atom lies on an inversion centre) and two tetrafluoroborate anions. The Fe atom is five-coordinate to four N atoms of the porphyrin ring and to one bridging O atom. The compound is characterized by an average Fe–N bond length of 2.064 Å. The Fe–O bond distance is 1.7665(11) Å and the Fe–O–Fe bond angle is 180.0° and the two porphyrin rings are parallel. Crystal data: crystal system, monoclinic, a = 8.867(3), b = 26.104(9), c = 15.748(6) Å, β = 105.40(3)°, space group, P2₁/c, V = 3514(2) Å³, Z = 2.     

Fluorescent Carbon Dot as Nanosensor for Sensitive and Selective Detection of Cefixime Based on Inner Filter Effect

Here a simple and sensitive fluorescent assay for detecting Cefixime based on inner filter effect (IFE) has been proven, which is conceptually different from the previously reported CEF fluorescent assays. In this sensing platform, fluorescent carbon dots (CDs) were prepared by one-pot synthesis and was directly used as fluorophore in IFE. The method is based on the complexation reaction between cefixime and palladium ion in the presence of acidic buffer solution (pH 4). The Pd(II)-CEFcomplex was capable of functioning as a powerful absorber in IFE to influence the excitation of fluorophore (CDs). Production Pd(II)-CEFcomplex induced the absorption band transition from 310 to 400 nm, which resulted in the complementary overlap with the excitation spectra of CDs. Due to the competitive absorption, the excitation of CDs was significantly weakened, resulting in the quenching of CDs. The present IFE-based sensing strategy showed a good linear relationship from 0.2 × 10^?6 M to 8 × 10^?6 M (R² = 0.987) and provided an exciting detection limit of 0.5 × 10^?7 (3δ/slope). The proposed method has been successfully applied for the determination of cefixime in raw milk and human urine samples.     

RF arbitrary waveform generation using tunable planar lightwave circuits

We demonstrate photonically-assisted generation of RF arbitrary waveforms using planar lightwave circuits (PLCs) fabricated on silica-on-silicon. We exploit thermo-optic effects in silica in order to tune the response of the PLC and hence reconfigure the generated waveform. We demonstrate the generation of pulse trains at 40 GHz and 80 GHz with flat-top, Gaussian, and apodized profiles. These results demonstrate the potential for RF arbitrary waveform generation using chip-scale photonic solutions.     

A practical two-step synthesis of imidazo[1,2-a]pyridines from N-(prop-2-yn-1-yl)pyridin-2-amines

The Sandmeyer reaction of differently C-2 substituted N-(prop-2-yn-1-ylamino)pyridines is an efficient, mild, new and practical method for the stereospecific synthesis of (E)-exo-halomethylene bicyclic pyridones bearing the imidazo[1,2-a]pyridine heterocyclic ring system.     

Phase Equilibrium Modeling of Clathrate Hydrates of Carbon Dioxide + 1,4-Dioxine Using Intelligent Approaches

In this work, an adaptive neuro-fuzzy inference system (ANFIS) and a couple of fuzzy logic approach and genetic algorithms are utilized to serve robust inverse-based approaches for determination/prediction of the clathrate hydrate formation pressure of carbon dioxide in the presence of 1,4-dioxine, which is a most-widely implemented water “soluble” organic promoter. The gained outcomes prove the reliability and accuracy of the suggested ANFIS approach with the mean square error of 0.0034 and squared correlation coefficients of 0.9969. Thanks to the results generated by the aforementioned intelligent approaches, the models proposed in the current research contribute to high accuracy for the estimations of the phase equilibria clathrate hydrates of carbon dioxide +1,4-dioxane.      

Synthesis and application of modified poly (styrene‐alt‐maleic anhydride) networks as a nano chelating resin for uptake of heavy metal ions

A chelating resin based on modified poly (styrene‐alt‐maleic anhydride) with 3‐aminobenzoic acid was synthesized. This modified resin was further reacted by 1,2‐diaminoethane or 1,3‐diaminopropane in the presence of ultrasonic irradiation to prepare tridimensional chelating resin for the removal of heavy metal ions from aqueous solutions. The adsorption behavior of Fe(II), Cu(II), Zn(II) and Pb(II) ions was investigated by synthesized chelating resins in various pH. Among the synthesized resins, CSMA‐AB1 and CSMA‐AB2 demonstrated a high affinity for the selected metal ions compared to SMA‐AB, and the order of removal percentage changes as follow: Fe(II) > Cu(II) > Zn(II) > Pb(II). The adsorption of all metal ions in acidic medium was moderate, and it was favored at the pH value of 6 and 7. Also, the prepared resins were examined for removal of metal ions from industrial wastewater and were shown to have a very efficient adsorption in the case of Cu(II), Fe(II) and Pb(II); however, the adsorption of Zn(II) was lower than others. The resin was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction analysis and thermogravimetric analysis/derivative thermogravimetry. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimized ultrasonic assisted extraction-dispersive liquid-liquid microextraction coupled with gas chromatography for determination of essential oil of Oliveria decumbens Vent

Ultrasonic assisted extraction-dispersive liquid-liquid microextraction (UAE-DLLME) coupled with gas chromatography (GC) was applied for extraction and determination of essential oil constituents of the plant Oliveria decumbens Vent. Scanning electron microscopy (SEM) was used to see the effect of ultrasonic radiation on the extraction efficiency. By comparison with hydrodistillation, UAE-DLLME is fast, low cost, simple, efficient and consuming small amount of plant materials (～1.0 g). The effects of various parameters such as temperature, ultrasonication time, volume of disperser and extraction solvents were investigated by a full factorial design to identify significant variables and their interactions. The results demonstrated that temperature and ultrasonication time had no considerable effect on the results. In the next step, a central composite design (CCD) was performed to obtain the optimum levels of significant parameters. The obtained optimal conditions were: 0.45 mL for disperser solvent (acetonitrile) and 94.84 μL for extraction solvent (chlorobenzene). The limits of detection (LODs), linear dynamic range and determination coefficients (R(2)) were 0.2-29 ng mL(-1), 1-2100 ng mL(-1) and 0.995-0.998, respectively. The main components of the essential oil were: thymol (47.06%), carvacrol (23.31%), gamma-terpinene (18.94%), p-cymene (8.71%), limonene (0.76%) and myristicin (0.63%).     

Optimization of dispersive liquid-liquid microextraction coupled with inductively coupled plasma-optical emission spectrometry with the aid of experimental design for simultaneous determination of heavy metals in natural waters

In this study, dispersive liquid-liquid microextraction (DLLME) combined with inductively coupled plasma optical emission spectrometry (ICP-OES) was developed for simultaneous preconcentration and trace determination of chromium, copper, nickel and zinc in water samples. Sodium diethyldithiocarbamate (Na-DDTC), carbon tetrachloride and methanol were used as chelating agent, extraction solvent and disperser solvent, respectively. The effective parameters of DLLME such as volume of extraction and disperser solvents, pH, concentration of salt and concentration of the chelating agent were studied by a (2^f−1) fractional factorial design to identify the most important parameters and their interactions. The results showed that concentration of salt and volume of disperser solvent had no effect on the extraction efficiency. In the next step, central composite design was used to obtain optimum levels of effective parameters. The optimal conditions were: volume of extraction solvent, 113 μL; concentration of the chelating agent, 540 mg L⁻¹; and pH, 6.70. The linear dynamic range for Cu, Ni and Zn was 1-1000 μg L⁻¹ and for Cr was 1-750 μg L⁻¹. The correlation coefficient (R²) was higher than 0.993. The limits of detection were 0.23-0.55 μg L⁻¹. The relative standard deviations (RSDs, C = 200 μg L⁻¹, n = 7) were in the range of 2.1-3.8%. The method was successfully applied to determination of Cr, Cu, Ni and Zn in the real water samples and satisfactory relative recoveries (90-99%) were achieved.     

Synthesis, structure, aggregation-induced emission, self-assembly, and electron mobility of 2,5-bis(triphenylsilylethynyl)-3,4-diphenylsiloles

2,5-Bis(triphenylsilylethynyl)-3,4-diphenylsiloles with different 1,1-substituents [XYSi(CPh)(2) (C-C≡C-SiPh(3))(2)] (Ph=phenyl) were synthesized in high yields by the Sonogashira coupling of 2,5-dibromo-3,4-diphenylsiloles with triphenylsilylacetylene, and two of these were characterized crystallographically. Crystal structures and theoretical calculations showed that the new silole molecules had higher conjugation than 2,5-diarylsiloles. They possessed low HOMO and LUMO energy levels due to the electron-withdrawing effect of the triphenylsilylethynyl groups. Cyclic voltammetry analysis revealed low electron affinities, which were comparable to those of perfluoroarylsiloles. B3LYP/6-31* calculations demonstrated that the new siloles possessed large reorganization energies for electron and hole transfers and high electron mobilities. A mobility of up to 1.2×10(-5) cm(2) V(-1) s(-1) was obtained by the transient electroluminescence method, which was about fivefold higher than that of tris(8-hydroxyquinolinato)aluminum, a widely used electron-transport material, under the same conditions. All of the silole molecules possessed high thermal stability. Although, their solutions were weakly emissive, their nanoparticle suspensions and thin films emitted intense blue-green light upon photoexcitation, demonstrating a novel feature of aggregation-induced emission (AIE). Polarized emissions were observed in the silole crystals. The addition of solvents, which did not dissolve the silole molecules, into silole-containing solutions caused self-assembly of the molecules, which produced macroscopic fibrils with strong light emissions.