Iron nanoparticles in aligned arrays of pure and nitrogen-doped carbon nanotubes

Arrays of aligned carbon nanotubes (CNTs) and nitrogen-doped carbon (CNx) nanotubes have been grown on silicon substrates as the result of thermolysis of ferrocene/toluene and ferrocene/acetonitrile mixture. The microstructure of materials was studied by transmission and scanning electron microscopy, and X-ray diffraction was used to control the carbon and iron forms. The composition and properties of iron nanoparticles developed in the CNT and CNx nanotube samples were determined from Mössbauer spectroscopy data. The total iron content in CNx nanotubes was found to be considerably higher than that in CNTs. Three forms of iron nanoparticles α-Fe, γ-Fe, and Fe3C were detected in CNTs and only two last of them in CNx nanotubes. In the interior of CNT channels the α-Fe and Fe3C nanoparticles were observed to be coupled by a strong exchange interaction and to exhibit magnetic behavior at room temperature.