Small Fe-Cu nanoparticles (NPs) (about 1 nm) supported at a high loading (over 10 wt %) on N-doped graphitic carbon have been prepared in a single pyrolytic step from chitosan adsorbing Cu 2+ and Fe 2+ salts. The presence of N atoms appears to be crucial in the formation of small-sized metallic NPs. Interactions between Fe and Cu are reflected by a shift in the binding energy to higher (Fe) or lower (Cu) values and by H 2 thermo-programmed reduction measurements, showing a new reduction peak at intermediate temperature (375 C) between that of Cu (175 C) and that of Fe (450 C). Fe-Cu NPs embedded within the N-doped graphitic carbon matrix are extremely active (TOF 315 h -1 ) and selective (no CO detected) catalysts for methanol reforming in the aqueous phase with stoichiometric H 2 O amounts to H 2 and CO 2 . The results achieved with Fe-Cu compare favorably with those reported in the literature for catalysts based on Pt, Pd, or Ru.
The orange dye-vanadium oxide (OD-V2O5) composite films were deposited from their aqueous suspension at various gravity conditions: at normal (positive) gravity (+1g) and negative gravity (-1g) by drop casting on to the surface type substrates having silver electrodes which were deposited by vacuum thermal evaporation. The aqueous suspension was prepared by dissolving and mixing OD and V2O5 in a distilled water with 2:1 wt%, respectively. The area of each silver electrode was 5x5 mm2 and the gap between two electrodes was 30 μm, while the thickness of composite films was 10 μm. The effect of humidity on electrical parameters (capacitance and impedance) of the films were studied and it was observed that with rising humidity the impedance of all the samples decreased up to 30333 times while the capacitance increased up to 2000 times. The samples deposited at +1g showed more sensitivity (-2.6 MΩ/%RH) towards humidity as compared to samples deposited at -1g (-1.89 MΩ/%RH). These results are explained by influence of positive and negative gravity, surface tension forces and composition of the solution on the film formation.
Carbon nanofibers (CNFs) randomly embedded in poly (lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most importantly, throughout all cytocompatibility experiments, cardiomyocytes were viable and expressed important biomarkers that were greatest on 50:50 wt% CNF:PLGA composites. The increased selective adsorption of fibronectin and vitronectin (critical proteins that mediate cardiomyocyte function) onto such composites proved to be the mechanism of action. However, the natural myocardium is anisotropic in terms of mechanical and electrical properties, which was not emulated in these prior PLGA:CNF composites. Thus, the aim of this in vitro study was to create and characterize CNFs aligned in PLGA composites (at 50:50 wt%, including their mechanical and electrical properties and cardiomyocyte density), comparing such results with randomly oriented CNFs in PLGA. Specifically, CNFs were added to soluble biodegradable PLGA (50:50 PGA:PLA weight ratio) and aligned by applying a voltage and then allowing the polymer to cure. CNF surface micron patterns (20 μm wide) on PLGA were then fabricated through a mold method to further mimic myocardium anisotropy. The results demonstrated anisotropic mechanical and electrical properties and significantly improved cardiomyocyte density for up to 5 days on CNFs aligned in PLGA compared with being randomly oriented in PLGA. These results indicate that CNFs aligned in PLGA should be further explored for improving cardiomyocyte density, which is necessary in numerous cardiovascular applications.
Metal organic frameworks (MOFs) are porous crystalline solids whose structure is formed by metal ions or clusters of a few metal ions held in place by bi- or multipodal organic linkers. In some cases, the metal nodes in MOFs have exchangeable coordination positions that allow them to participate as active sites promoting organic reactions. There is much current interest in exploiting the advantages that MOFs offer as catalysts, including a large surface area, high metal content, flexibility in the design of the active sites in the framework, together with the easy synthesis of these materials. In the present review we describe the use of MOFs as catalysts to promote cross-coupling reactions involving organometallic reaction intermediates and catalysis by Lewis acid sites. These types of reactions are of large synthetic utility due to the high yields achieved, mild conditions and compatibility with other functional groups. The content includes C-C bond forming reactions, such as Suzuki-Miyaura, Mizoroki-Heck, Sonogashira, Stille and Ullmann, but also C-O and C-N cross-couplings. The final section summarizes our views on future developments and targets in these types of reactions. The core of the review is references that have appeared in 2010 or after, which give an idea of the novelty and current interest in this area.
Treatment of the dichlorodicarbonyl ruthenium(II) [Ru(CO)2Cl2]n with bidentate 1,2,4-triazoles, 1,2,4-triazines and pyrimidine derivatives in refluxing ethanol or in THF yielded stable, octahedral yellow or pale-yellow solids. All the complexes have been characterized by IR, 1 H NMR spectroscopy and elemental analyses.
