The aim of this work is to investigate the possibility of extracting correct structural parameters from fluorescence EXAFS data taken at high count rates with an energy-resolving detector. This situation is often encountered on third-generation synchrotron radiation sources which provide a high flux on the sample. Errors caused by pulse pile-up in the extraction of structural information have been quantified in a real experiment, and different approaches to the problem of data correction have been elaborated. The different approaches are discussed in a comparison of the ability of each kind of correction to recover the correct structural parameters. The result of our analysis is that it is possible to work in non-linear conditions and correct the data, if the response of the acquisition system is known. Reliable structural information can be obtained with data acquired up to a count rate equal to approximately 60% of the inverse of the dead time.
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http://dx.doi.org/10.1107/S0909049504002122 | DOI Listing |
J Phys Chem A
December 2024
Advanced Computing, Mathematics and Data Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States.
The fact that the photoabsorption spectrum of a material contains information about the atomic structure, commonly understood in terms of multiple scattering theory, is the basis of the popular extended X-ray absorption spectroscopy (EXAFS) technique. How much of the same structural information is present in other complementary spectroscopic signals is not obvious. Here we use a machine learning approach to demonstrate that within theoretical models that accurately predict the EXAFS signal, the extended near-edge region does indeed contain the EXAFS-accessible structural information.
View Article and Find Full Text PDFDalton Trans
January 2025
Department of Chemistry, Purdue University, West Lafayette, Indiana 47906, USA.
Peroxynitrite (ONOO) is a highly reactive nitrogen species that can cause significant damage to proteins, lipids, and DNA. Various enzymes, including metalloenzymes, play crucial roles in reducing ONOO concentrations to protect cellular components. While the interaction of ONOO with heme proteins is well known, the reduction by Cu-containing proteins is less studied.
View Article and Find Full Text PDFNanoscale
December 2024
Department of Chemistry, National Institute of Technology, Rourkela, 769008, India.
As nanocrystalline materials exhibit complex disorders, assessment of the local disorder at the nanoscale induced by implanted lattice defects plays a crucial role in understanding the structure-function relationship in these materials. In this report, a comprehensive structural analysis was performed on upconverting nanocrystals (UCNCs) of NaYF/Nd/Yb/Tm, containing varying concentrations of Li to induce deliberate lattice defects. Subsequently, a comprehensive structural analysis of the UCNCs was performed using synchrotron radiation-based high-resolution X-ray diffraction (HRXRD), high-energy total angle scattering coupled with pair distribution function (PDF) analysis, neutron diffraction (ND) and EXAFS probing.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
College of Chemistry, Chemical Engineering and Environment, Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Micro-Nano Organic Optical Materials Laboratory, Minnan Normal University, Zhangzhou 363000, China.
The type of coordinated N atoms in the metal-N coordination structure is of paramount importance to the catalytic property of N-modified carbon-based single-atom catalysts (SACs). Extended X-ray absorption fine structure (EXAFS) spectroscopy is a powerful tool for analyzing the coordination environments of SACs. Despite its efficacy, the limited availability of synchrotron light sources and the complexity of data analysis have constrained its broader application in identifying metal-N coordination types within SACs.
View Article and Find Full Text PDFJ Phys Chem B
November 2024
Dipartimento di Chimica, "La Sapienza" Università di Roma, P.le Aldo Moro 5, 00185 Rome, Italy.
The hydration properties of the Pb ion in aqueous solution have been investigated by using a synergic approach based on Classical and Car-Parrinello molecular dynamics (CPMD) simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy. A definite answer has been given to the main question on the Pb hydration structure, which concerns the formation of either holodirected or hemidirected solvation geometries, such terms referring to the arrangements of the ligands that can be directed either throughout the surface of an encompassing globe around Pb or throughout only part of the globe, respectively. Our CPMD results show that the Pb ion in water forms a hemidirected 4-fold cluster with a well-defined distorted pyramidal geometry.
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