Evidence of band gap features in Fe3O4 Bbmm filled carbon nano-onions

A key challenge in the fabrication of ferromagnetically filled multilayer fullerenes (carbon nano-onions, CNOs) is the manipulation of the structure, composition and electronic band characteristics of both the carbon layers and encapsulated ferromagnetic material. Interestingly, a recent work has demonstrated that the addition of small quantities of water during the chemical vapour synthesis of Fe3C filled CNOs can allow the local manipulation of the Fe3C crystal-structure and induce the nucleation of a novel high pressure Bbmm Fe3O4 crystal-phase. In this report we propose an advanced study of such structural transition. Particularly, we investigate the morphological, optical (band-gap) characteristics and magnetic properties of the as produced CNO materials by using transmission electron microscopy, vibrating sample magnetometry, x-ray photoelectron spectroscopy and UV-vis spectroscopy.