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Extended X-ray absorption fine structure
About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.
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TL;DR: In this article, perovskite-type compounds of general formula LaMn1−xCuxO3 were prepared by calcining the citrate gel precursors at 823, 923, and 1073 K, and the oxides were investigated by means of elemental analysis (atomic absorption and redox titration), X-ray powder diffraction, and magnetic susceptibility.
116 citations
TL;DR: The first direct measurements over a range of temperatures from 25-350°C are reported for cation-oxygen (water) distances in aqueous solutions at equilibrium saturated vapour pressures.
116 citations
TL;DR: In this article, polyvinylpyrrolidone (PVP) was used as the polymer stabilizer for the synthesis of bimetallic nanoparticles containing Au and Pd using co-reduction and sequential reduction strategies.
Abstract: Bimetallic nanoparticles containing Au and Pd were synthesized using poly(vinylpyrrolidone) (PVP) as the polymer stabilizer using both co-reduction and sequential reduction strategies. The nanoparticle structures and catalytic activities for the aerobic oxidation of crotyl alcohol to crotonaldehyde at room temperature in the absence of base were investigated. The chemical, structural, and electronic properties of these nanoparticles were investigated using Pd-K-edge and Au-LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and Pd-LIII and Au-LIII edge X-ray absorption near edge structure (XANES) spectroscopy. EXAFS analysis for the sequentially reduced bimetallic systems indicates the presence of significantly Pd-enriched surfaces and Au cores. XANES spectra of the Pd-LIII edges indicated that the sequentially reduced particles showed significant d-charge depletion compared to pure monometallic Pd and co-reduced AuPd nanoparticles. The sequentially reduced nanoparticles with Pd rich s...
116 citations
TL;DR: In this paper, a combined Raman spectroscopy-X-ray absorption study showed a significantly altered structure of the molybdenum oxide phase after dehydration, the total Mo-Mo coordination number drops from 3.27 to 0.20 after anin situ thermal treatment at 673 K.
Abstract: In contrast to the frequently reported lack of interaction between hexavalent molybdenum and SiO2 and the tendency of silica-supported MoO3 to coalescence, it has been found that on dehydration small molybdenum oxide clusters spread over a silica support. A combined Raman spectroscopy-X-ray absorption study shows a significantly altered structure of the molybdenum oxide phase after dehydration. In EXAFS the total Mo-Mo coordination number drops from 3.27 to 0.20 after anin situ thermal treatment at 673 K. The increase of the peak in the XANES region (Is -→ 4d) indicates that the coordination sphere of the molybdenum atoms strongly alters after dehydration. The Raman spectra reflect the change of the structure through a shift of the position of the terminal Mo=O bond from 944 to 986 cm−1 and the disappearance of the bridged Mo-O-Mo vibration at 880 cm−1. It is concluded that dehydration produces almost isolated molybdenum sites in this highly dispersed sample. Water ligands stabilize the oligomeric clusters under ambient conditions; the removal of water causes spreading of these clusters.
116 citations
TL;DR: In this paper, a technique for investigation of the infrared absorption of water vapor and carbon dioxide under simulated atmospheric conditions has been developed, which includes a 22m multiple-traversal absorption cell which permits controlled variation of the following parameters: (1) geometrical path length, pressure of absorbing gas, (2) pressure of nonabsorbing gases nitrogen and oxygen, and (3) the temperature of the gaseous mixture.
Abstract: A technique for investigation of the infrared absorption of water vapor and carbon dioxide under simulated atmospheric conditions has been developed. The “total absorption” or area under the curve giving fractional absorption as a function of frequency can be determined for each spectral region in which characteristic absorption occurs. The apparatus includes a 22-m multiple-traversal absorption cell which permits controlled variation of the following parameters: (1) geometrical path length, (2) pressure of absorbing gas, (3) pressure of the nonabsorbing gases nitrogen and oxygen, and (4) the temperature of the gaseous mixture. A prism spectrometer is used to measure fractional absorption as a function of frequency under various experimental conditions. Although the observed shape of a given absorption band depends upon the effective slit widths of the spectrometer, the total absorption of a band depends, within wide limits, only on the foregoing listed parameters. For the range of temperatures encountered in the lower atmosphere, the influence of temperature variation on total absorption is so small that it can be neglected. On the basis of results obtained by the techniques described, it is possible to make accurate predictions of absorption of infrared radiation in the earth’s atmosphere.
116 citations