For instance, two sites with identical EXAFS spectra can nevertheless have distinct XANES spectra. The XANES region is quite sensitive to small structural variations. Experimentally, this has been proven true. In principle, one can argue that it is possible to determine the three-dimensional structure of the absorbing atom to its environment from analysis of the XANES features. Moreover, multiple scattering is particularly important in the XANES region. Since higher oxidation-states implies shorter bond lengths in molecules, the edge energies increases as the oxidation-states increases.Īs stated above, XANES is oxidation sensitive. As the absorber–scatterer distance gets shorter, the energy of the continuum state increases as 1/R 2. An example is the potential well created by the absorbing and scattering (between nearest neighboring) atoms. A continuum resonance refers to a short lived the excitation process in which a core electron is excited into a higher energy state that is usually above the continuum. This interpretation treats the edge features as continuum resonances. However, an alternative interpretation of edge energies is more suitable. The nanoscale core/shell heterostructure is a particularly efficient motif to combine the promising properties of plasmonic materials and rare-earth compounds however, there remain significant challenges in the synthetic control due to the large interfacial energy between these two intrinsically unmatched materials. This observation can be explained using an electrostatic model: atoms with a higher oxidation state require more energetic X-ray to excite its core electron because the nucleus is less-shielded and carries a higher effective charge. In the present work, we fabricated these NS via a one-pot chemical reaction. For example, dichloromethane (CH 2Cl 2) is nearly opaque to low energy X-rays, and this will cause complication in data interpretation if dichloromethane is largely present in the sample or used as the solvent.Īs the oxidation-state of the absorption site increases, the absorption edge energy increases correspondingly. A core/shell NS represents an alternative geometry with characteristic sizes in the same nanometer range that is worth exploring as a candidate for a fast Pd-based magnetic hydrogen-gas sensor. In cases of certain samples or solvents, the incoming X-ray photons could be nearly completely absorbed, and leaves the detector little signal to detect. This method is limited to moderately concentrated samples (eg.
0 kommentar(er)
