XAFS characterization

NegotiableUpdate on 02/09

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Nature of the Manufacturer: Producers

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Overview

XAFS characterization obtains information about the local electronic structure, atomic structure, and chemical environment of the central absorbing atom by measuring the absorption coefficient of the sample for X-rays as a function of the incident photon energy. This curve exhibits oscillation phenomena on the high-energy side of the absorption edge, which are caused by the interference effect of photoelectron waves excited by X-rays and scattered waves from neighboring atoms.

Product Details

XAFS (X-ray Absorption Fine Structure) characterization is a technique based on X-ray absorption spectroscopy used to analyze the local structure and chemical environment of materials at the atomic scale. The following is a detailed introduction to XAFS characterization:

1、 Basic principles of XAFS characterization

X-ray Absorption Near Edge Structure (XANES):

Located near the absorption edge (approximately 30-50 eV), it is highly sensitive to the oxidation state, coordination configuration, and electronic state of the central absorption atom. By analyzing the peak positions, intensities, and shapes of XANES spectra, this information can be qualitatively or semi quantitatively obtained.

Expand X-ray Absorption Fine Structure (EXAFS):

After covering the absorption edge, the higher energy range (about 50-1000 eV) can be achieved. Fourier transform is used to convert the energy space oscillation into a radial distribution function (R-space), which can quantitatively analyze the structural parameters such as the type, distance, coordination number, and disorder of the coordinating atoms around the central absorption atom.

2、 Technical advantages of XAFS characterization

Atomic scale resolution:

Being able to detect the local environment of individual atoms in materials, including the type, distance, and coordination number of coordinating atoms, provides microstructural basis for understanding material properties.

Not dependent on long-range ordered structures:

Unlike traditional diffraction techniques, XAFS characterization does not require the sample to have crystallinity and is suitable for structural analysis of amorphous, highly disordered materials (such as solutions, glasses), and nanomaterials.

Chemical environmental sensitivity:

Highly sensitive to the oxidation state and coordination chemical environment (such as the type and bond length of coordination atoms) of central absorption atoms, it can reveal the dynamic changes of materials in chemical reactions or physical processes.

In situ characterization capability:

It can be equipped with various in-situ reaction devices to monitor the structural evolution of materials in real-time under harsh conditions such as high temperature, high pressure, and electrochemistry, providing key data for studying reaction mechanisms.

Element universality:

It can measure the XAFS spectra of almost all elements in the periodic table, including light elements (such as carbon and oxygen) and transition metal elements, and is suitable for the analysis of multi-component complex systems.

3、 Application areas of XAFS characterization

Nanomaterial research:

Analyze the size, morphology, and surface coordination structure of nanoparticles to reveal the chemical and biological mechanisms at the interface between nanomaterials and biological systems.

Catalytic Science:

Characterize the atomic level structure of the active center of the catalyst and understand the catalytic reaction mechanism. For example, XAFS technology can reveal the dynamic changes of active species in dilute alloy catalysts, providing theoretical guidance for the rational design of efficient catalysts.

Energy materials:

Study the oxidation state changes of active materials, local structural evolution of electrode materials, and electrolyte electrode interface interactions during the charging and discharging process of ion batteries. XAFS characterization provides solid theoretical support for the development of higher performance ion batteries.

biomedical science:

Analyze the coordination environment of metal cofactors in biomolecules and understand the functional mechanisms of biomolecules. For example, XAFS technology can characterize the local coordination structure of iron atoms in ferritin nanoenzymes, revealing differences in their activity in scavenging superoxide radicals.

Environmental Science:

Study the distribution and transformation mechanism of pollutants to provide scientific basis for environmental governance. Can analyze the chemical forms and binding modes of heavy metal pollutants in the environment, and assess their ecological risks.

4、 Experimental methods for XAFS characterization

Transmission method:

Suitable for transparent samples such as films and powders, the absorption coefficient can be obtained by measuring the intensity ratio of incident X-rays and transmitted X-rays.

Fluorescence method:

Suitable for low concentration or thick samples, obtaining absorption information by detecting the fluorescence signal generated by X-ray excitation of the sample.

Total reflection method:

Combining the principle of total reflection to improve surface sensitivity, suitable for research in surface science and thin film materials.

In situ characterization technique:

Combining XAFS characterization with electrochemical cells, high-temperature furnaces, high-pressure devices, etc., to achieve structural evolution monitoring of materials under real working conditions.