XANES particle size determination

Figure 10 The effect of particle size on the change in the normalized Pt J-band vacancies d-band vacancies/% surface atoms) (...) in going from 0.54 to 0.0 V. The change in the Pt-Pt coordination number as determined from the Pt L3 edge EXAFS analysis is also shown (—). The ordinate axis refers to the change in the J-band vacancy/atom determined from XANES spectra normalized with respect to total number of surface atoms present (based on cluster calculations on a cubo-octahedron model). 

The depth of introduction of radiation determines whether the properties of bulk phases or the interface may be studied, or, in other words, how thick the studied layer is. The energy of the radiation and the size of the particles influence the depth of introduction and, consequently, the thickness of the studied layer. For example, x-ray radiation is introduced into the phases depending on the energy at high x-ray energies the radiation is introduced deeply, so the properties of the bulk can be studied by x-ray diffraction or x-ray fluorescence analysis. At smaller x-ray energies (up to 1000 eV), the structure of the surface layer can be studied by the XANES and EXAFS methods. The same stands for electron and ion radiation. 

Analysis of the extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) of mixtures of salts and zeolites before and after heat-treatment enables us to prove or disprove that a solid-state reaction has occurred. Moreover, EXAFS is a tool to determine the coordination of cations introduced via SSIE into the zeolite matrix. If these cations are reducible to the zero-valent state as, e.g., Pt + or Pd + cations are, EXAFS also provides information about the size of the metal particles generated by reduction. To date, unfortunately, only a few pertinent studies have been reported (cf., e.g., [40] and Sect. 5.4.2). 

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