The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film and bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption spectroscopy (TDS), and density functional theory (DFT). On both surfaces, XPS and TDS indicate D2O and CO2 chemisorb at room temperature with broad thermal desorption peaks (423–723 K) and a peak desorption temperature near 573 K. A comparison of thermal desorption Redhead activation energies to adsorption energies calculated using DFT indicates that defect surface sites are important for the observed strong adsorbate-surface reactivity. Numerical calculations of the competetive adsorption/desorption equilibria for H2O and CO2 on SrTiO3(001) surfaces show that for typical atmospheric concentrations of 0.038% carbon dioxide and 0.247% water vapor the surfaces are covered to a large extent with both adsorbates. The high desorption temperature indicates that these adsorbates have the potential to impact measurements of the electronic structure of BaTiO3–SrTiO3(001) surfaces exposed to air, or prepared in high vacuum deposition systems, as well as the electrical properties of thin film ATiO3-based devices.

Adsorption and reactions of NO on clean and CO-precovered Ir(111) were investigated by means of X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HR-EELS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption (TPD). Two NO adsorption states, indicative of fcc-hollow sites and atop sites, were present on the Ir(111) surface at saturation coverage. NO adsorbed on hollow sites dissociated to Na and Oa at temperatures above 283 K. The dissociated Na desorbed to form N2 by recombination of Na at 574 K and by a disproportionation reaction between atop-NO and Na at 471 K. Preadsorbed CO inhibited the adsorption of NO on atop sites, whereas adsorption on hollow sites was not affected by the coexistence of CO. The adsorbed CO reacted with dissociated Oa and desorbed as CO2 at 574 K.

No abstract

No abstract

Treatment of alkyl trialkylsilyl ethers with 0.5 mol% of Sc(OTf) 3 combined with 5 equivalents of water in acetonitrile provides an efficient and practical method for the deprotection of silyl ethers. Alcoholic trialkylsilyl ethers have been cleaved selectively in the presence of phenolic trialkylsilyl ethers.

For the fully hydrated multilamellar stack of dimyristoylphosphatidylcholine (DMPC) fluid membranes containing hydrophobic peptide gramicidin A (GrA), the membrane thickness and the bilayer-bilayer separation (i.e., water layer thickness) were determined by measuring small-angle X-ray scattering and the density of aqueous suspensions of DMPC-GrA mixtures. When the molar ratio of GrA to DMPC was 0.04, the membrane thickness decreased by 2-3 A by the incorporation of GrA molecules into DMPC bilayers, whereas the water layer thickness increased by 3-4 A. As the cause of the increment of water layer thickness, two possibilities were considered; (1) attractive van der Waals force acting between the bilayer membranes weakened by the decrease of membrane thickness, and (2) repulsive undulation force enhanced by the incorporation of GrA which may stabilize the gauche conformers of the lipid acyl chains.

No abstract

No abstract