A fluorescence XAFS measurement instrument in the soft x-ray region toward observation under operando conditions

Journal Article · Sun Mar 15 00:00:00 EDT 2015 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4913653· OSTI ID:22392427

Baba, Y.; Shimoyama, I.; Sekiguchi, T. ^[1]

---

1. Quantum Beam Science Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

X-ray absorption fine structure (XAFS) measurements are widely used for the analysis of electronic structure. Generally, XAFS in the soft X-ray region is measured under vacuum, but chemical structures under vacuum are typically different from those under operando conditions, where chemical species exhibit their function. Here, we developed an XAFS measurement instrument, as a step toward operando fluorescent, which yields XAFS measurement using synchrotron radiation in the soft X-ray region. We applied this method to analyze the local electronic structure of the sulfur atoms in L-cysteine in different pH solutions. In water at pH 7, the hydrogen atom does not dissociate from the thiol (-SH) group in L-cysteine, which forms a structure surrounded by and interacting with water molecules. The XAFS spectrum of L-cysteine in solution was altered by changing the pH. At pH 9, the hydrogen atom dissociated and a thiolate anion was formed. Although the -SH group was oxidized to SO{sub 4}{sup 2−} when L-cysteine was adsorbed on a metal surface and dried, no oxidation was observed in solution. This may be because the water molecules were densely packed and protected the -SH group from oxidation. Our results show that this instrument aimed toward operando fluorescence XAFS measurements in the soft X-ray region is useful for structural analysis of sulfur atoms in organic molecules in air and in solution. The instrument will be applied to the structural analysis of materials containing elements that have absorption edges in soft X-ray region, such as phosphorus and alkali metals (potassium and cesium). It will be also particularly useful for the analysis of samples that are difficult to handle under vacuum and materials that have specific functions in solution.

• OSTI ID: 22392427
• Journal Information: Review of Scientific Instruments, Vol. 86, Issue 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ABSORPTION SPECTROSCOPY
ANIONS
CESIUM
CYSTEINE
ELECTRONIC STRUCTURE
FINE STRUCTURE
FLUORESCENCE
HYDROGEN
MOLECULES
PHOSPHORUS
POTASSIUM
SOFT X RADIATION
SOLUTIONS
SPECTRA
SULFUR
SYNCHROTRON RADIATION
X-RAY SPECTROSCOPY