Advantages of soft X-ray absorption over TEM-EELS for solid carbon studies––a comparative study on diesel soot with EELS and NEXAFS Original Research Article

Diesel soot was investigated with electron energy loss spectroscopy (EELS) and near edge X-ray absorption fine structure spectroscopy (NEXAFS). The EELS spectra were obtained in connection with transmission electron microscopy studies, whereas the NEXAFS were obtained from a scanning transmission X-ray microscope (STXM) and from a conventional NEXAFS beamline at two synchrotron facilities. The X-ray absorption spectra show molecular species, aliphatics, such as carboxyl, and C–H bonds, which are not visible in EELS spectra of the same material. In particular, EELS fails to detect surface-functional groups, which can be detected with NEXAFS. Since numerous works on molecular carbon structure determined with TEM-EELS have been published, it is possible that these results have to be reassessed.