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Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.


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TL;DR: Hard X-ray analysis has significantly contributed to the understanding of catalytic reactions as discussed by the authors, in particular through the use of Xray absorption spectroscopy the chemical state and local neighborhood of a chemical species involved in the catalytic reaction can be investigated.
Abstract: Hard X-ray analysis has significantly contributed to the understanding of catalytic reactions. In particular, through the use of X-ray absorption spectroscopy the chemical state and local neighborhood of a chemical species involved in the catalytic reaction can be investigated, shedding light on the reaction mechanisms. As this technique does not rely on crystalline order, it can also be employed on non-crystalline solids and in the liquid phase. In addition, X-ray scattering can yield the nano structure such as the mesoscopic particle morphology in small-angle scattering and the atomic order in (poly-)crystalline samples. One key advantage of hard X-rays for studying catalytic reactions is their large penetration depth in matter that allows one to investigate the chemical state in operando, e.g., inside a chemical reactor under reaction conditions [1, 2]. It is thus also complementary to other spectroscopic techniques (e.g., micro IR, Raman, XRD, XRF), including electron microscopy (cf. for example [3, 4]).

8 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the mechanism of controlled modification of composition, structure, chemistry, physicochemical and process properties of columbite, tantalite, zircon and feldspar at the meso-, micro-and nanoscales after nonthermal treatment by high-voltage nanosecond electromagnetic pulses.
Abstract: The authors have studied the mechanism of controlled modification of composition, structure, chemistry, physicochemical and process properties of columbite, tantalite, zircon and feldspar at the meso-, micro- and nanoscales after nonthermal treatment by high-voltage nanosecond electromagnetic pulses. The studies used methods: X-ray photoelectron spectroscopy, scanning electron and atomic force microscopy, potentiometric titration, electromigration chromatography, Kelvin probe force microscopy, microhardness metering and assessment of hydrophobic behavior and flotation activity of the minerals. It is found that changes in the chemical state of atoms on the surface of minerals are mainly connected with the sequential transformation of stages in the process of formation and modification of a functional cover of mineral surface, with variation in a ratio of different type hydroxyl groups on the surface of columbite, zircon and feldspar, which conditions contrast physicochemical properties of rare metal minerals and improves selectivity of their separation by flotation.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the structure and chemical states of a catalyst developed by immobilizing palladium on S-terminated GaAs(001) were studied using hard x-ray photoelectron spectroscopy (HX-PES).
Abstract: We present studies on the structure and chemical states of a catalyst developed by immobilizing palladium on S-terminated GaAs(001). Hard x-ray photoelectron spectroscopy (HX-PES) of core-level and valence band photoemission consistently indicates that the organopalladium molecules are reduced on the surface yielding Pd nanoparticles with a metallic nature. This finding is supported by high-resolution observations using scanning electron microscopy and backscattered electron image. HX-PES results also reveal that a portion of S atoms forming the S-termination is oxidized during the formation of Pd nanoparticles.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the chemical composition of alumina films grown on Si(100) at different substrate temperatures by metalorganic chemical vapor deposition (MOCVD) using aluminium acetylactonate {Al(acac)3} as the precursor.
Abstract: We have studied the chemical composition of alumina (Al2O3) films grown on Si(100) at different substrate temperatures by metalorganic chemical vapor deposition (MOCVD) using aluminium acetylactonate {Al(acac)3} as the precursor. We have found that the resulting films of Al2O3 contain substantial amounts of carbon. X-ray photoelectron spectroscopy (XPS) was employed to study the chemical state of carbon present in such films. The XPS spectrum reveals that the carbon present in Al2O3 film is graphitic in nature. Auger electron spectroscopy (AES) was employed to study the distribution of carbon in the Al2O3 films. The AES depth profile reveals that carbon is present throughout the film. The AES study on Al2O3 films corroborates the XPS findings. An investigation of the Al2O3/Si(100) interface was carried out using cross-sectional transmission electron microscopy (XTEM). The TEM study reveals textured growth of alumina film on Si(100), with very fine grains of alumina embedded in an amorphous carbon-containing matrix.

8 citations

Journal ArticleDOI
TL;DR: In this paper, the contribution of the shift from polarization of the ligands following core photoionization is discussed, and the use of this methodology is illustrated using the vanadium ion in V2O5 and CeVO4, including its lithium-intercalated form.
Abstract: X-ray photoelectron spectroscopy (XPS) is known, mainly, as a technique for surface analysis. It is especially valued for interpretation of the chemical state by means of the chemical shift. This paper concerns the contribution to this shift from polarization of the ligands following core photoionization. Intercalation of ions such as lithium will influence the electronic polarizability of the oxygen ions and hence the value of the Auger parameter (AP). The AP is the difference in kinetic energy of the Auger peak in the spectrum and that of the principal photoelectron peak, calculated by an internationally accepted procedure. Thus, while obtaining the composition and chemical state of a compound one can also determine the polarizability of the material. Polarizability is crucial to the dielectric properties of oxides, such as refractive index, and is of value in optimizing intercalation compounds for use in optoelectronic devices. The use of this methodology will be illustrated using the vanadium ion in V2O5 and CeVO4, including its lithium-intercalated form. Copyright © 2002 John Wiley & Sons, Ltd.

8 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202326
202249
202184
202089
201987
201894