scholarly journals X-ray Absorption Spectroscopic Characterization of Solid Acid-base Catalysts

2014 ◽  
Vol 57 (6) ◽  
pp. 261-270 ◽  
Author(s):  
Takashi Yamamoto
Keyword(s):  
Solid Acid ◽  
Spectroscopic Characterization ◽  
Acid Base ◽  
X Ray ◽  
Base Catalysts ◽  
X Ray Absorption

scholarly journals Cu+-specific CopB transporter: Revising P1B-type ATPase classification

2018 ◽  
Vol 115 (9) ◽  
pp. 2108-2113 ◽  
Author(s):  
Rahul Purohit ◽  
Matthew O. Ross ◽  
Sharon Batelu ◽  
April Kusowski ◽  
Timothy L. Stemmler ◽  
...  
Keyword(s):  
Maximal Activity ◽  
Spectroscopic Characterization ◽  
Spectroscopic Studies ◽  
Divalent Metal Ions ◽  
X Ray ◽  
Reducing Environment ◽  
Methionine Residues ◽  
Cellular Copper ◽  
X Ray Absorption

The copper-transporting P1B-ATPases, which play a key role in cellular copper homeostasis, have been divided traditionally into two subfamilies, the P1B-1-ATPases or CopAs and the P1B-3-ATPases or CopBs. CopAs selectively export Cu+ whereas previous studies and bioinformatic analyses have suggested that CopBs are specific for Cu2+ export. Biochemical and spectroscopic characterization of Sphaerobacter thermophilus CopB (StCopB) show that, while it does bind Cu2+, the binding site is not the prototypical P1B-ATPase transmembrane site and does not involve sulfur coordination as proposed previously. Most important, StCopB exhibits metal-stimulated ATPase activity in response to Cu+, but not Cu2+, indicating that it is actually a Cu+ transporter. X-ray absorption spectroscopic studies indicate that Cu+ is coordinated by four sulfur ligands, likely derived from conserved cysteine and methionine residues. The histidine-rich N-terminal region of StCopB is required for maximal activity, but is inhibitory in the presence of divalent metal ions. Finally, reconsideration of the P1B-ATPase classification scheme suggests that the P1B-1- and P1B-3-ATPase subfamilies both comprise Cu+ transporters. These results are completely consistent with the known presence of only Cu+ within the reducing environment of the cytoplasm, which should eliminate the need for a Cu2+ P1B-ATPase.

Spectroscopic Characterization of the Nitridation Process of Polymeric Precursors to SI-M-N-O Systems (M=Ti, Zr, Al)

1992 ◽  
Vol 287 ◽  
Author(s):  
F. Babonneau ◽  
G. D. Soraru
Keyword(s):  
Spectroscopic Characterization ◽  
Ceramic Materials ◽  
Spectroscopic Techniques ◽  
X Ray ◽  
Nitridation Process ◽  
Local Environments ◽  
Ceramic Precursors ◽  
Mixed Ceramic ◽  
X Ray Absorption

ABSTRACTA commercial polycarbosilane was modified with various metallic alkoxides to get mixed ceramic precursors in the Si-M-C-O systems (M=Ti, Zr Al). Pyrolysis under ammonia leads to the formation of various ceramic materials depending on the nature of M : Si3N4/TiN, Si3N4/ZrO2 or β′-SiAlON phases.The polymer-to-ceramics conversion have been studied by MAS-NMR (29 Si, 27Al) and X-ray absorption (Ti K-edge). This paper will show how these two complementary spectroscopic techniques can be used to follow the nitridation process by probing local environments of different elements. In addition, it will be pointed out how X-ray absorption can be a powerful tool for the detection of the crystallization of nitride cubic phases.

Structural and spectroscopic characterization of an Fe(VI) bis(imido) complex

Science ◽  
2020 ◽  
Vol 370 (6514) ◽  
pp. 356-359 ◽  
Author(s):  
Jorge L. Martinez ◽  
Sean A. Lutz ◽  
Hao Yang ◽  
Jiaze Xie ◽  
Joshua Telser ◽  
...  
Keyword(s):  
Double Resonance ◽  
Spectroscopic Characterization ◽  
Biological Processes ◽  
X Ray Diffraction ◽  
Electron Nuclear Double Resonance ◽  
X Ray ◽  
High Valent ◽  
X Ray Absorption ◽  
Structure Calculations

High-valent iron species are key intermediates in oxidative biological processes, but hexavalent complexes apart from the ferrate ion are exceedingly rare. Here, we report the synthesis and structural and spectroscopic characterization of a stable Fe(VI) complex (3) prepared by facile one-electron oxidation of an Fe(V) bis(imido) (2). Single-crystal x-ray diffraction of 2 and 3 revealed four-coordinate Fe centers with an unusual “seesaw” geometry. 57Fe Mössbauer, x-ray photoelectron, x-ray absorption, and electron-nuclear double resonance (ENDOR) spectroscopies, supported by electronic structure calculations, support a low-spin (S = 1/2) d3 Fe(V) configuration in 2 and a diamagnetic (S = 0) d2 Fe(VI) configuration in 3. Their shared seesaw geometry is electronically dictated by a balance of Fe-imido σ- and π-bonding interactions.

Spectroscopic Characterization of a Pre-Ceramic Polymer For Sic/Tic System.

1990 ◽  
Vol 180 ◽  
Author(s):  
Florence Babonneau ◽  
Patrice Barre ◽  
Jacques Livage ◽  
Michel Verdaguer
Keyword(s):  
Spectroscopic Characterization ◽  
Argon Atmosphere ◽  
Mas Nmr ◽  
Spectroscopic Techniques ◽  
Excess Carbon ◽  
X Ray ◽  
Local Environments ◽  
X Ray Absorption ◽  
Cp Mas Nmr

ABSTRACTPolytitanocarbosilane precursor for SiC/TiC ceramics was characterized by various spectroscopic techniques (29Si and 13C CP MAS NMR, Ti K-edge XANES and EXAFS) in order to follow how titanium ions are incorporated into the polycarbosilane-based polymer. This polymer has been fired in argon atmosphere, and the evolution of the local environments of Si and Ti atoms, during the pyrolysis process, have been followed using 29Si MAS-NMR and Ti K-edge X-ray absorption: this study reveals the formation of Si-O bonds above 500°C, while Ti-C bonds clearly appear around 800°C. Above 1000°C, Si-O bonds are consumed by reaction with excess carbon and the system finally crystallizes into SiC/TiC mixture above 1200°C.

scholarly journals Spectroscopic characterization of electronic structures of ultra-thin single crystal La0.7Sr0.3MnO3

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chun-Chien Chiu ◽  
Yao-Wen Chang ◽  
Yu-Cheng Shao ◽  
Yu-Chen Liu ◽  
Jenn-Min Lee ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Treatment Process ◽  
Spectroscopic Characterization ◽  
Absorption Effect ◽  
X Ray ◽  
Lsmo Film ◽  
X Ray Scattering ◽  
X Ray Absorption ◽  
Transmission And Reflection

AbstractWe have successfully fabricated high quality single crystalline La0.7Sr0.3MnO3 (LSMO) film in the freestanding form that can be transferred onto silicon wafer and copper mesh support. Using soft x-ray absorption (XAS) and resonant inelastic x-ray scattering (RIXS) spectroscopy in transmission and reflection geometries, we demonstrate that the x-ray emission from Mn 3s-2p core-to-core transition (3sPFY) seen in the RIXS maps can represent the bulk-like absorption signal with minimal self-absorption effect around the Mn L3-edge. Similar measurements were also performed on a reference LSMO film grown on the SrTiO3 substrate and the agreement between measurements substantiates the claim that the bulk electronic structures can be preserved even after the freestanding treatment process. The 3sPFY spectrum obtained from analyzing the RIXS maps offers a powerful way to probe the bulk electronic structures in thin films and heterostructures when recording the XAS spectra in the transmission mode is not available.

Soft X-ray Spectroscopic Characterization of Montmorillonite

2008 ◽  
Vol 1124 ◽  
Author(s):  
Jan-Erik Rubensson ◽  
Franz Hennies ◽  
Lars O Werme ◽  
Ola Karnland
Keyword(s):  
Absorption Spectrum ◽  
Silicon Oxide ◽  
Spectroscopic Characterization ◽  
Aluminum Oxides ◽  
Complex Samples ◽  
X Ray ◽  
Pure Silicon ◽  
Local Electronic Structure ◽  
X Ray Absorption

AbstractSoft X-ray spectroscopy was applied to study a calcium bentonite from the Kutch area in India. We recorded the X-ray absorption spectra from the L-edge of calcium, silicon, and aluminum, and from K-edge of oxygen. The Ca absorption spectrum shows a quasi-atomic behavior, while the Si spectrum closely simulates the absorption spectrum of a pure silicon oxide. The O K spectrum shows a pre-peak, which is absent in the spectra of both the pure, bulk aluminum and silicon oxides. The Al L spectrum is complex and shows almost no resemblance to the absorption spectrum of aluminum oxides. The chemical state of the Al atoms (in octahedral coordination) must, thus, be quite different from what is common in the oxides. The obtained data show that soft X-ray spectroscopy is a promising technique for studying clay minerals. It is capable of supplying unique information that is complementary to information accessible using other techniques; especially, it can be used to determine the local electronic structure at various atomic sites in the complex samples.

Sign in / Sign up

Export Citation Format

Share Document