Optical activity in the biaryl series

The relationship between the CD spectra of the chiral biaryls and their stereochemical configuration, as a function of the dihedral angle between the molecular planes of the aromatic moieties, has been investigated for biphenyl, 1,1′-binaphthyl, 1,1′-bianthryl and 9,9′-bianthryl in the exciton approximation and, for the 1,1′-binaphthyls, in the π-SCF approximation. Both methods provide unambiguous assignments of absolute configuration except for biaryls with a critical dihedral angle of π/2 in those with effective D_data2 chromophoric symmetry, or 100–110° in the case of the 1,1′-binaphthyls.     

Cerium oxide nanoparticles scavenge nitric oxide radical (˙NO)

In this study we have obtained evidence that cerium oxide nanoparticles (CeO(2) NPs) are able to scavenge nitric oxide radical. Surprisingly, this activity is present in CeO(2) NPs with a lower level of cerium in the 3+ state (CeO(2) NPs with low 3+/4+ ratio and therefore a reduced number of oxygen vacancies), in contrast to the superoxide scavenging properties which are correlated with an increased level of cerium in the 3+ state (CeO(2) NPs with high 3+/4+ ratio and therefore an increased number of oxygen vacancies).     

Performance enhancement of phosphoric acid fuel cell using phosphosilicate gel based electrolyte

Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed for performance enhancement of phosphoric acid fuel cell(PAFC).Phosphosilicate gel in paste form and in powder form is synthesized from tetraethoxysilane and orthophosphoric acid using sol-gel method for two different P/Si ratio of 5 and 1.5 respectively.Replacement of phosphoric acid electrolyte by phosphosilicate gel paste enhances the peak power generation of the fuel cell by 133% at 120 ℃ cell temperature;increases the voltage generation in the ohmic regime and extends the maximum possible load current.Polyinyl alcohol(PVA) is used to bind the phosphosilicate gel powder and to form the hybrid crosslinked gel polymer electrolyte membrane.Soaking the membrane with phosphoric acid solution,instead of that with water improves the proton conductivity of the membrane,enhances the voltage and power generation by the fuel cell and extends the maximum possible operating temperature.At lower operating temperature of 70 ℃,peak power produced by phosphosilicate gel polymer electrolyte membrane fuel cell(PGMFC) is increased by 40% compared to that generated by phosphoric acid fuel cell(PAFC).However,the performance of composite membrane diminishes as the cell temperature increases.Thus phosphosilicate gel in paste form is found to be a good alternative of phosphoric acid electrolyte at medium operating temperature range while phosphosilicate gel-PVA composite offers performance enhancement at low operating temperatures.     

Solution-based chemical synthesis of boehmite nanofibers and alumina nanorods

This article reports an easy chemical method of synthesizing boehmite nanofibers by a modified sol-gel process involving aluminum isopropoxide precursor. Nanorods of gamma-alumina have been successfully prepared after dehydration of the viscous sol at 600 degrees C for 4 h in air. The boehmite nanofibers and gamma-alumina nanorods were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy for surface chemistry and functional groups, scanning electron microscopy, high-resolution transmission electron microscopy with selected area electron diffraction, and energy-dispersed spectroscopy for morphology and structure identification. The length of the boehmite nanofibers was found to be more than 10 mum with a crystalline lattice structure. The mechanism of formation of the boehmite nanofibers included the preferential growth along the longitudinal axis due to interaction between the solvent molecules and the surface OH- groups of hydrogen bonds. It is also suggested that the boehmite nanofibers may have formed due to the inherent instability of the planar structure of the boehmite lattice. The diameter of the gamma-alumina nanorods was found to be less than 10 nm with a varying length in the range of 50-200 nm. Boehmite to gamma-Al2O3 transformation was attributed to the loss of water molecules by internal condensation of protons and hydroxyl ions.     

PEGylated inorganic nanoparticles

Application of inorganic nanoparticles in diagnosis and therapy has become a critical component in the targeted treatment of diseases. The surface modification of inorganic oxides is important for providing diversity in size, shape, solubility, long-term stability, and attachment of selective functional groups. This Minireview describes the role of polyethylene glycol (PEG) in the surface modification of oxides and focuses on their biomedical applications. Such a PEGylation of surfaces provides "stealth" characteristics to nanomaterials otherwise identified as foreign materials by human body. The role of PEG as structure-directing agent in synthesis of oxides is also presented.     

Ueber einige Eigenschaften des Rhodanions

Ohne Zusammenfassung