X-ray absorption, photoemission spectroscopy, and Raman scattering analysis of amorphous tantalum oxide with a large extent of oxygen nonstoichiometry

The electronic structure and modification of the local interatomic structure of a reactive sputtered amorphous tantalum oxide (a-TaO(x)) thin film with the variation of oxygen nonstoichiometry, x in a-TaO(x) have been investigated by X-ray absorption spectroscopy (XAS), X-ray photoemission spectroscopy (XPS), Raman scattering spectroscopy, and Rutherford back scattering spectroscopy. A parallel chemical shift of Ta4f(7/2) and O1s core levels observed with the variation of x indicates the Fermi level shift by reduction and oxidation in the framework of the rigid band model. Extended X-ray absorption fine structure (EXAFS) suggests both the increase of average coordination number of the first Ta-O shell in polyhedra and a considerable reduction of the average Ta-O bond length with the increase of x. The relative intensity of Raman shift peaks at 670 cm(-1) and 815 cm(-1), corresponding to Ta-O stretching of TaO(6) octahedra and TaO(5) probably with a pyramidal form, respectively, drastically changes between x = 2.47 to 1.86, suggesting the change in the predominant polyhedron from TaO(6) to TaO(5) with a modification in multiplicity of oxygen by the reorganization of the polyhedral network.     

An Advanced Materials Beamline for Energy Research (AMBER)

Detailed mapping of the electronic structure is a crucial part of explaining the behavior of materials. It is the electronic structure that determines the conductivity and thermal properties. It is the electronic structure that determines chemical properties. Knowledge about the electronic structure can help in determining the atomic structure of molecules.     

ESI-MS detection of proposed reaction intermediates in the air-promoted and ligand-modulated oxidative Heck reaction

Electrospray ionization mass spectrometry (ESI-MS) and subsequent MS/MS analyses were used to directly detect palladium-containing cationic reaction intermediates in a ligand controlled palladium(II)-catalyzed oxidative Heck arylation. All potential intermediates were observed as dmphen-ligated palladium(II) species, suggesting that the dmphen bidentate ligand is attached to the metal center during the entire catalytic cycle. The study supports previous mechanistic propositions and provides new information regarding the composition of aryl-containing Pd(II) complexes in an ongoing oxidative Heck reaction. In addition, sodium acetate was found to be a useful base alternative to previously used tertiary amines.     

In situ soft X-ray absorption spectroscopy investigation of electrochemical corrosion of copper in aqueous NaHCO3 solution

A novel electrochemical setup has been developed for soft X-ray absorption studies of the electronic structure of electrode materials during electrochemical cycling. In this communication we illustrate the operation of the cell with a study of the corrosion behavior of copper in aqueous NaHCO₃ solution via the electrochemically induced changes of its electronic structure. This development opens the way for in situ investigations of electrochemical processes, photovoltaics, batteries, fuel cells, water splitting, corrosion, electrodeposition, and a variety of important biological processes.     

Ultrafast chemistry: cobalt carbonyl-mediated synthesis of diaryl ketones under microwave irradiation

By combining the advantages of metal activation, in situ carbon monoxide delivery, and microwave heating, benzophenones were efficiently synthesized in 6-10 s. These ultrafast carbonylation reactions occur under air by flash heating of aryl iodides in the presence of dicobalt octacarbonyl. [reaction: see text]     

Fast isolation of hydrophobic organic environmental contaminants from exposed semipermeable membrane devices (SPMDs) prior to GC analysis

Semipermeable membrane devices (SPMD) represent a passive sampling technology that is becoming widely used for monitoring of surface waters pollution. While "classic" procedures employ dialysis to recover target compounds from exposed SPMDs, in the present study analytes were isolated from cut membrane together with sequestering medium (triolein) using hexane as an extraction solvent. This approach allowed us to reduce the time needed for accomplishment of isolation step from 48 h to only 1 h. Automated gel permeation chromatography (GPC) clean-up is employed in the following step to separate triolein from analytes fraction. Musk compounds (MCs), polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) and several other persistent organochlorine compounds (OCs) were determined in the respective fraction by GC method employing selective detectors (MSD, ECD). As shown in a series of analyses of SPMDs deployed in various aquatic ecosystems, high recoveries and good repeatability of results together with a possibility to obtain the information on the pollution of sampling site at the day of sample arrival to laboratory make this newly implemented procedure an interesting alternative to time consuming dialysis.