Micro-X-ray absorption near-edge structure

Techniques of microscopic XRF ( j,-XRF) developed in the last 20 years provide 2D images and elemental maps of each element present in the target material. Portable/in situ p-XRF, j,-XRF spectrometers synchrotron-based ( -SRXRF) and micro-x-ray absorption spectroscopy/micro-x-ray absorption near-edge structure spectroscopy (XAS/ J,-XANES) have improved the mineralogical characterization, as well as the elemental and chemical imaging of samples at the submicrometer scale [61]. 

Bonnin-Mosbah M, Metrich N, Susini J, Salome M, Massare D, Menez (2002) Micro X-ray absorption near edge structure at the sulfur and iron -edges in natural silicate glasses. Spectrochim Acta ... 

It could be concluded that, elements that can be hyperaccumulated include As (>0.1 %), Cd (>0.01 %), Co (>0.1 %), Cu (>0.1 %), Pb (>0.1 %), Mn (>1 %), Ni (>0.1 %), Se (>0.1 %) and Zn (>1 %). It could be also mentioned that, the element levels accumulated in these plants would be lethal to other organisms, yet cause no toxicity in hyperaccnmulators. The Se-tolerance mechanism of hyperaccumulators can be followed by nsing microfocused X-ray fluorescence (pXRF) mapping and micro-X-ray absorption near edge structure (pXANES) spectroscopy, which revealed a stark contrast in spatial distribution and chemical speciation of Se between hyperaccnmnlators and nonaccumulators. 

In 2006, Lobinski et al.1 reported on the imaging and speciation analysis of trace elements to study the element distribution, oxidation state, metal site and metal structure in biological environments using mass spectrometric techniques (LA-ICP-MS, SIMS, MALDI-MS) and non-mass-spectrometric techniques such as micro-PIXE (proton induced X-ray emission), XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) -the latter two techniques are very sensitive due the use of a more intense synchrotron beam.1... 

X-ray absorption near edge structure(XANES) and electron energy loss near edge structure(ELNES) show similar spectra, thus almost the same theoretical analysis is valid both for these spectroscopies. The careful analysis including higher excited atomic orbitals in the basis set reproduce very well the spectral structure even in details. The core-hole effects are sometimes very important in the excited state electronic state. The theoretical analysis by the cluster model calculation provides very useful information on the local electronic property and the micro structure. 

Near-edge X-ray absorption flne structure spectroscopy (STXM/NEXAFS) and optical spectroscopy coupled with micro-FTIR have been used to detect the presence of an equilibrium between malonic acid and its enol form on deliquesced micrometer particles [45]. The amount of enol increases with the amount of water that is present (Figure 3.34). 

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