Energy dispersive X-ray spectrometry and electron energy-loss spectroscopy
Energy-dispersive X-ray spectroscopy (EDX) is used to analyze the elemental composition of solid surfaces. X-ray emission is stimulated by the irradiation of the surface with a high energy beam of charged particles or a focused X-ray beam. Excitation of the electronic structure of an atom can produce an X-ray emission, the energy signature of which is a unique characteristic of each element. Therefore a “fingerprint” or “signature” spectrum can be obtained allowing element identification via comparison with reference spectra. Electron microscopes often contain the instrumentation to perform EDX analysis, as the technology required to generate a high energy beam of charged particles, i.e., electrons, is already present. Electron energy-loss spectroscopy (EELS) requires the use of electrons with much lower energies than EDX, typically a beam of 100-1000 eV energy. These electrons are detected upon their reflection from a surface, and the loss of energy due to their interaction with the surface material is used to determine information regarding its chemical structure. Similarly to XRD, EDX and EELS are used extensively for the characterization of crystalline biomaterials (Konigsberger and Konigsberger, 2006; Naka and Carney, 2006; DiMasi and Gower, 2014; Aparicio and Ginebra, 2015).