Probing the structure of Fe nanoparticles in multiwall carbon nanotubes grown on a stainless steel substrate”

We investigated the local order in individual iron nanoparticles (NPs) embedded in carbon nanotubes (CNTs). The NPs directly come from the CNT growth on stainless steel without addition of external metal catalyst. The structural analysis has been obtained through nanoscale transmission extended electron energy loss fine structure (EXELFS) measurements above the iron L2,3 edge. A theoretical simulation of the EXELFS features has been performed within the multiple scattering theory. By comparing the experimental data with the simulations, we found that pure c-Fe and Fe3C nanoparticles are the catalysts of the CNT synthesis on the stainless steel. Moreover, from the analysis of the fine details of the EXELFS oscillations, we also estimated the value of the fcc Fe NP lattice parameter to be a =3.61 ± 0.03 A ° . This last finding suggests a high magnetic moment of the fcc Fe NPs.