Unsupervised machine learning for unbiased chemical classification in X-ray absorption spectroscopy and X-ray emission spectroscopy

2021 ◽  
Author(s):  
Samantha Tetef ◽  
Niranjan Govind ◽  
Gerald T. Seidler
Keyword(s):  
Machine Learning ◽  
Absorption Spectroscopy ◽  
Emission Spectroscopy ◽  
Emission Spectra ◽  
Relevant Information ◽  
Unsupervised Machine Learning ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

We utilize unsupervised machine learning to extract chemically relevant information in X-ray absorption near-edge structure (XANES) and in valence-to-core X-ray emission spectra (VtC-XES) for classification of an ensemble of sulphorganic molecules.

Automatic oxidation threshold recognition of XAFS data using supervised machine learning

2019 ◽  
Vol 4 (5) ◽  
pp. 1014-1018 ◽  
Author(s):  
Itsuki Miyazato ◽  
Lauren Takahashi ◽  
Keisuke Takahashi
Keyword(s):  
Machine Learning ◽  
Absorption Spectroscopy ◽  
Supervised Machine Learning ◽  
Oxidation States ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Oxidation states of materials are characterized by the X-ray absorption near edge structure (XANES) region in X-ray absorption spectroscopy (XAS).

scholarly journals High-energy resolution X-ray absorption and emission spectroscopy reveals insight into unique selectivity of La-based nanoparticles for CO2

2015 ◽  
Vol 112 (52) ◽  
pp. 15803-15808 ◽  
Author(s):  
Ofer Hirsch ◽  
Kristina O. Kvashnina ◽  
Li Luo ◽  
Martin J. Süess ◽  
Pieter Glatzel ◽  
...  
Keyword(s):  
Energy Resolution ◽  
Emission Spectroscopy ◽  
High Energy ◽  
Unit Cell ◽  
High Energy Resolution ◽  
Electron Configuration ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

The lanthanum-based materials, due to their layered structure and f-electron configuration, are relevant for electrochemical application. Particularly, La2O2CO3 shows a prominent chemoresistive response to CO2. However, surprisingly less is known about its atomic and electronic structure and electrochemically significant sites and therefore, its structure–functions relationships have yet to be established. Here we determine the position of the different constituents within the unit cell of monoclinic La2O2CO3 and use this information to interpret in situ high-energy resolution fluorescence-detected (HERFD) X-ray absorption near-edge structure (XANES) and valence-to-core X-ray emission spectroscopy (vtc XES). Compared with La(OH)3 or previously known hexagonal La2O2CO3 structures, La in the monoclinic unit cell has a much lower number of neighboring oxygen atoms, which is manifested in the whiteline broadening in XANES spectra. Such a superior sensitivity to subtle changes is given by HERFD method, which is essential for in situ studying of the interaction with CO2. Here, we study La2O2CO3-based sensors in real operando conditions at 250 °C in the presence of oxygen and water vapors. We identify that the distribution of unoccupied La d-states and occupied O p- and La d-states changes during CO2 chemoresistive sensing of La2O2CO3. The correlation between these spectroscopic findings with electrical resistance measurements leads to a more comprehensive understanding of the selective adsorption at La site and may enable the design of new materials for CO2 electrochemical applications.

X-ray absorption spectroscopy and density functional analysis of the Fe3+ distribution profile on Al sites in a chrysoberyl crystal, BeAl2O4:Fe3+

2016 ◽  
Vol 49 (2) ◽  
pp. 385-388 ◽  
Author(s):  
Kanokwan Kanchiang ◽  
Atipong Bootchanont ◽  
Janyaporn Witthayarat ◽  
Sittichain Pramchu ◽  
Panjawan Thanasuthipitak ◽  
...  
Keyword(s):  
Optical Properties ◽  
Absorption Spectroscopy ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Distribution Profile ◽  
Laser Applications ◽  
Edge Structure ◽  
X Ray ◽  
Site Distribution ◽  
X Ray Absorption

Chrysoberyl is one of the most interesting minerals for laser applications, widely used for medical purposes, as it exhibits higher laser performance than other materials. Although its utilization has been vastly expanded, the location of transition metal impurities, especially the iron that is responsible for chrysoberyl's special optical properties, is not completely understood. The full understanding and control of these optical properties necessitates knowledge of the precise location of the transition metals inside the structure. Therefore, synchrotron X-ray absorption spectroscopy (XAS), a local structural probe sensitive to the different local geometries, was employed in this work to determine the site occupation of the Fe3+ cation in the chrysoberyl structure. An Fe K-edge X-ray absorption near-edge structure (XANES) simulation was performed in combination with density functional theory calculations of Fe3+ cations located at different locations in the chrysoberyl structure. The simulated spectra were then qualitatively compared with the measured XANES features. The comparison indicates that Fe3+ is substituted on the two different Al2+ octahedral sites with the proportion 60% on the inversion site and 40% on the reflection site. The accurate site distribution of Fe3+ obtained from this work provides useful information on the doping process for improving the efficiency of chrysoberyl as a solid-state laser material.

X-ray absorption spectroscopy studies for the determination of adsorption binding modes of selenium oxoanions onto iron and manganese based nanomaterials

2012 ◽  
Vol 1480 ◽  
Author(s):  
Christina M. Gonzalez ◽  
Jason G. Parsons ◽  
Jeffrey Hernandez ◽  
Jorge L. Gardea-Torresdey
Keyword(s):  
Absorption Spectroscopy ◽  
Binding Modes ◽  
Edge Structure ◽  
X Ray ◽  
Microwave Assisted ◽  
Spectroscopy Studies ◽  
X Ray Absorption ◽  
Binding Mechanisms ◽  
Iron And Manganese

ABSTRACTIncreasing concentrations of selenium oxoanions in the environment are placing many animals at risk for reproduction failure and deformities. The understanding of binding mechanisms of selenium oxoanions to iron and manganese based oxide minerals could lead to enhanced understanding of selenium mobility in the environment. In this study, the binding mechanisms of selenium oxoanions, selenite and selenate, to non microwave-assisted and microwave-assisted synthetic Fe3O4, Mn3O4, and MnFe2O4 nanomaterials were investigated through the use of X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) spectroscopy studies revealed the oxidation state of selenite and selenate remains the same after binding occurs to all nanomaterials in pH 2, 4, or 6 environments. The binding modes of selenite and selenate were determined to be bidentate binuclear through use of Extended x-ray absorption fine structure (EXAFS) and were independent of nanomaterials, synthetic technique, and pH.

Oxidation State of Ti Atoms and Ti-O Bond Length on Natural Sapphire Gem-Materials Probed by X-Ray Absorption Spectroscopy

2017 ◽  
Vol 737 ◽  
pp. 585-589 ◽  
Author(s):  
Natthapong Monarumit ◽  
Wiwat Wongkokua ◽  
Somruedee Satitkune
Keyword(s):  
Bond Length ◽  
Oxidation State ◽  
Absorption Spectroscopy ◽  
Germanium Detector ◽  
Blue Color ◽  
Edge Structure ◽  
X Ray ◽  
Fe Content ◽  
X Ray Absorption ◽  
Exafs Spectra

Sapphire, an inorganic gem-material in a variety of corundum, mainly consists of alpha-alumina (α-Al2O3) structure. The geological origins of sapphire are related to either basaltic or metamorphic rocks. The causes of the color on sapphire are some trace elements such as Cr, Fe, and Ti. It could be mentioned that Ti atoms have cooperated with Fe atoms for creating the blue color. In this study, X-ray absorption spectroscopy (XAS) technique focused on the x-ray absorption near edge structure (XANES) and the extended x-ray absorption fine structure (EXAFS) is employed to identify the oxidation state of Ti atoms and Ti-O bond length on sapphire samples. The Ti K-edge XANES and EXAFS spectra of natural sapphires were carried out using the 13-channel array germanium detector in fluorescence mode. The XANES spectra showed that the oxidation state of Ti was Ti4+ regardless of Fe content. Moreover, the Ti-O bond length on a-Al2O3 was equal to the Ti-O bond length on rutile (TiO2) analyzed from the EXAFS spectra. From these results, it could be concluded that the oxidation state of Ti atoms on natural sapphires was Ti4+ which substitutes Al3+ on the sapphire structure.

scholarly journals Vanadium K-edge X-ray-absorption spectroscopy of the functioning and thionine-oxidized forms of the VFe-protein of the vanadium nitrogenase from Azotobacter chroococcum

1989 ◽  
Vol 258 (3) ◽  
pp. 733-737 ◽  
Author(s):  
J M Arber ◽  
B R Dobson ◽  
R R Eady ◽  
S S Hasnain ◽  
C D Garner ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Absorption Spectroscopy ◽  
Azotobacter Chroococcum ◽  
Vanadium Atom ◽  
Oxidation States ◽  
Edge Structure ◽  
X Ray ◽  
Vanadium Nitrogenase ◽  
Enzyme Turnover ◽  
X Ray Absorption

Vanadium K-edge X-ray-absorption spectra were collected for samples of thionine-oxidized, super-reduced (during enzyme turnover) and dithionite-reduced VFe-protein of the vanadium nitrogenase of Azotobacter chroococcum (Acl*). Both the e.x.a.f.s and the x.a.n.e.s. (X-ray-absorption near-edge structure) are consistent with the vanadium being present as part of a VFeS cluster; the environment of the vanadium is not changed significantly in different oxidation states of the protein. The vanadium atom is bound to three oxygen (or nitrogen), three sulphur and three iron atoms at 0.215(3), 0.231(3) and 0.275(3) nm respectively.

scholarly journals Simultaneous two-color X-ray absorption spectroscopy using Laue crystals at an inverse-compton scattering X-ray facility

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
Juanjuan Huang ◽  
Benedikt Günther ◽  
Klaus Achterhold ◽  
Martin Dierolf ◽  
Franz Pfeiffer
Keyword(s):  
Compton Scattering ◽  
Absorption Spectroscopy ◽  
Bimetallic Catalyst ◽  
Structural Information ◽  
Synergistic Effects ◽  
Edge Structure ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
X Ray Absorption

X-ray absorption spectroscopy (XAS) is an element-selective technique that provides electronic and structural information of materials and reveals the essential mechanisms of the reactions involved. However, the technique is typically conducted at synchrotrons and usually only probes one element at a time. In this paper, a simultaneous two-color XAS setup at a laboratory-scale synchrotron facility is proposed based on inverse Compton scattering (ICS) at the Munich Compact Light Source (MuCLS), which is based on inverse Compton scattering (ICS). The setup utilizes two silicon crystals in a Laue geometry. A proof-of-principle experiment is presented where both silver (Ag) and palladium (Pd) K-edge X-ray absorption near-edge structure spectra were simultaneously measured. The simplicity of the setup facilitates its migration to other ICS facilities or maybe to other X-ray sources (e.g. a bending-magnet beamline). Such a setup has the potential to study reaction mechanisms and synergistic effects of chemical systems containing multiple elements of interest, such as a bimetallic catalyst system.

Sign in / Sign up

Export Citation Format

Share Document