Micromotor‐Based Biomimetic Carbon Dioxide Sequestration: Towards Mobile Microscrubbers

We describe a mobile CO₂ scrubbing platform that offers a greatly accelerated biomimetic sequestration based on a self‐propelled carbonic anhydrase (CA) functionalized micromotor. The CO₂ hydration capability of CA is coupled with the rapid movement of catalytic micromotors, and along with the corresponding fluid dynamics, results in a highly efficient mobile CO₂ scrubbing microsystem. The continuous movement of CA and enhanced mass transport of the CO₂ substrate lead to significant improvements in the sequestration efficiency and speed over stationary immobilized or free CA platforms. This system is a promising approach to rapid and enhanced CO₂ sequestration platforms for addressing growing concerns over the buildup of greenhouse gas.     

Search for the global minimum structures of AlB3H2n (n = 0 − 6) clusters

The global minimum structures of AlB₃H_2n (n = 0–6) clusters are determined using the stochastic search method at the B3LYP/6–31G level of theory. These initially specified geometries are recalculated using B3LYP and CCSD(T) methods using the 6–311++G^** basis set. The structural and electronic properties of the two lowest‐lying isomers are presented. The structural parameters obtained for aluminum borohydride are compared with the experimental and theoretical results. The H₂ fragmentation energies of the most stable isomers are investigated. Chemical bonding analyses for the global minimum of AlB₃H_2n (n = 0–6) clusters are performed using the adaptive natural density partitioning method. © 2014 Wiley Periodicals, Inc.     

Rhodium‐catalyzed transfer hydrogenation with aminophosphines and analysis of electrical characteristics of rhodium(I) complex/n‐Si heterojunctions

A series of novel neutral mononuclear rhodium(I) complexes of the P―NH ligands have been prepared starting from [Rh(cod)Cl]₂ complex. Structural elucidation of the complexes was carried out by elemental analysis, IR and multinuclear NMR spectroscopic data. The complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1‐phenylethanol derivatives in the presence of 2‐propanol as the hydrogen source. Catalytic studies showed that all complexes are also excellent catalyst precursors for transfer hydrogenation of aryl alkyl ketones in 0.1 m iso‐PrOH solution. In particular, [Rh(cod)(PPh₂NH―C₆H₄―4‐CH(CH₃)₂)Cl] acts as an excellent catalyst, giving the corresponding alcohols in excellent conversion up to 99% (turnover frequency ≤ 588 h^?1). Furthermore, rhodium(I) complexes have been used in the formation of organic–inorganic heterojunction by forming their thin films on n‐Si and evaporating Au on the films. It has been seen that the structures have rectifying properties. Their electrical properties have been analyzed with the help of current–voltage measurements. Finally, it has been shown that the complexes can be used in the fabrication of temperature and light sensors. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparative study of boron compounds and aluminum trihydroxide as flame retardant additives in epoxy resin

The aim of this study was to investigate and compare the flame retardant properties of boron compounds with respect to aluminum trihydroxide (ATH) in an epoxy system based on bisphenol A epichlorohydrin‐based epoxy resin and cycloaliphatic polyamine‐based hardener. Six different boron compounds including colemanite (C), ulexite (U), boric acid (BA), boric oxide (BO), melamine borate (MB) and guanidinium nonaborate (GB) were used as flame retardant additive. The flame retardant properties of epoxy‐based composites were investigated using limiting oxygen index (LOI), UL 94 standards both in vertical and horizontal position, thermogravimetric analysis, cone calorimeter and scanning electron microscopy. According to flammability test results, boron compounds except for C and U showed better performance than ATH. According to the LOI results, 40% BA containing sample had the highest LOI value of 28.5, while 30% MB, 35% GB and 40% BA containing samples had the highest UL 94V rating (V0). According to the cone calorimeter test results, all boron containing samples had better fire performances than ATH containing sample; 40 wt% BO containing sample showed the lowest peak heat release rate, average heat release rate and total heat release values. Copyright © 2014 John Wiley & Sons, Ltd.     

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME–SFO) was for the first time combined with field‐amplified sample injection (FASI) in CE to determine four β₂‐agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting‐out extraction, β₂‐agonists were extracted into ACN that was then used as the disperser solvent in DLLME–SFO. Optimum DLLME–SFO conditions were: 1.0 mL ACN, 50 μL 1‐undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β₂‐agonists into CE. Compared to conventional CZE, DLLME–SFO–FASI–CE achieved sensitivity enhancement factors of 41–1046 resulting in LODs in the range of 1.80–37.0 μg L^?1. Linear dynamic ranges of 0.15–10.0 mg L^?1 for cimbuterol and 15–1000 μg L^?1 for the other analytes were obtained with coefficients of determination (R²) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β₂‐agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.     

Cadmium,lead, copper and manganese determination in human deciduous teeth by electrothermal atomic absorption spectrometry using a lanthanum,palladium and citric acid mixture as chemical modifier

Cadmium, lead, copper and manganese were determined in human deciduous teeth and bone ash 1400 standard reference material by electrothermal atomic absorption spectrometry (ETAAS), using a lanthanum + palladium + citric acid (CA) modifier mixture. Optimum masses and mass ratios of La, La + Pd and La + Pd + CA modifiers for analytes in bone ash 1400 sample solution were investigated. Pyrolysis and atomization temperatures of analytes in a tooth sample solution were obtained with and without modifiers. The mixture of La + Pd + CA was found to be preferable for the determination of analytes in tooth samples and bone ash 1400, dissolved in a mixture of HNO₃ + H₂O₂. The detection limits and characteristic masses of analytes were obtained with or without modifiers based on integrated absorbance for tooth sample solution (2% m/v). The detection limits obtained with La + Pd + CA are 6,24,16 and 46 ng g^?1 for Cd, Cu, Mn and Pb, respectively. Recovery tests for analytes in bone ash 1400 and a tooth solution with La and La + Pd + CA modifier mixture were studied and compared with certified and non certified values. The La + Pd + CA mixture was also applied to the determination of Cd, Pb, Cu and Mn in tooth samples.     

Synthesis,characterization and first application of chiral C2‐symmetric bis(phosphinite)–Pd(II) complexes as catalysts in asymmetric intermolecular Heck reactions

A series of new chiral C₂‐symmetric bis(phosphinite) ligands and their palladium(II) complexes have been synthesized and for the first time used as catalysts in the palladium‐catalysed asymmetric intermolecular Heck coupling reactions of 2,3‐dihydrofuran with iodobenzene or aryl triflate. Under optimized conditions, products were obtained with high conversions and moderate to good enantioselectivities. The new C₂‐symmetric bis(phosphinite) ligands and their palladium(II) complexes were characterized using multinuclear NMR and Fourier transform infrared spectroscopies and elemental analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

Halogenation of a twisted non-polar π-system as a tool to modulate phosphorescence at room temperature

Halogenation of a twisted three-fold symmetric hydrocarbon with F, Cl or Br leads to strong modulation of triplet–triplet annihilation and dual phosphorescence, one thermally activated and the other very persistent and visible by eye, with different relative contributions depending on the halide. The room temperature phosphorescence is highly unusual given the absence of lone-pair-contributing heteroatoms. The interplay between the spin–orbit coupling matrix elements and the spatial configuration of the triplet state induces efficient intersystem crossing and thus room temperature phosphorescence even without relying on heteroatomic electron lone pairs. A ninefold increase of the ISC rate after introduction of three bromine atoms is accompanied by a much higher 34-fold increase of phosphorescence rate.

Twisted π-systems investigation showed a very unusual HAE, influencing independently the ISC and the dual phosphorescence emission, one being very persistent at room temperature and visible by eye in powder.     

The effect of H2O on the sulfation of Havelock limestone under oxy-fuel conditions in a thermogravimetric analyser

A gas mixture representing oxy-fuel combustion conditions was employed in a thermogravimetric analyser to determine the effect of water vapor and SO₂ concentration on limestone sulfation kinetics over the temperature range of 800 to 920 °C. Here, experiments used small samples of particles (4 mg), with small particle sizes (d_p < 38 µm) and large gas flow rates (120 mL/min@NTP) in order to minimize mass transfer interferences. The gas mixture contained 5000 ppm_v SO₂, 2% O₂, and the H₂O content was changed from 0% to 25% with the balance CO₂. When water vapor was added to the gas mixture at lower temperatures (800–870 °C), the limestone SO₂ capture efficiency increased. However, as the temperature became higher, the enhancement in total conversion values decreased. As expected, Havelock limestone at higher temperatures (890 °C, 920 °C, and 950 °C) experienced indirect sulfation and reacted at a faster rate than for lower temperatures (800–870 °C) for direct sulfation over the first five minutes of reaction time. However, the total conversion of Havelock limestone for direct sulfation was generally greater than for indirect sulfation.     

New route to synthesis of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Heck and Suzuki cross‐coupling reactions

Herein we report a new method for the synthesis and characterization of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Suzuki coupling and Heck reactions of aryl bromides with phenylboronic acid and styrene, respectively, under mild conditions. The PVP‐stabilized palladium(0) nanoclusters with a particle size of 4.5 ± 1.1 nm were prepared using a new method: refluxing a mixture of potassium tetrachloropalladate(II) and PVP in methanol at 80 °C for 1 h followed by reduction with sodium borohydride. Palladium(0) nanoclusters prepared in this way were stable in solution for weeks, could be isolated as solid materials and were characterized by TEM, XPS, UV–vis, and XRD techniques. The PVP‐stabilized palladium(0) nanoclusters were active catalysts in Heck and Suzuki coupling reactions of arylbromides with styrene and phenylboronic acid affording stilbenes and biphenyls, respectively, in high yield. Recycling experiments showed that PVP‐stabilized palladium(0) nanoclusters could be used five times with essentially no loss in activity in the Heck and Suzuki coupling reactions. Copyright © 2009 John Wiley & Sons, Ltd.