Stable Fe nanomagnets encapsulated inside vertically-aligned carbon nanotubes

• Published in: Physical chemistry chemical physics : PCCP 2017-12, Vol.19 (47), p.3279-3285
• Main Authors: Bondino, Federica, Magnano, Elena, Ciancio, Regina, Castellarin Cudia, Carla, Barla, Alessandro, Carlino, Elvio, Yakhou-Harris, Flora, Rupesinghe, Nalin, Cepek, Cinzia
• Format: Article
• Language: English
• Subjects: BCC metals; Carbon nanotubes; Coercivity; Electron microscopy; Encapsulation; Iron; Magnetic properties; Nanoparticles; Nanotubes; Remanence; Soft x rays; Substrates; Surface stability
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp05181f

Well-defined sized (5-10 nm) metallic iron nanoparticles (NPs) with body-centered cubic structure encapsulated inside the tip of millimeter-long vertically aligned carbon nanotubes (VACNTs) of uniform length have been investigated with high-resolution transmission electron microscopy and soft X-ray spectroscopy techniques. Surface-sensitive and chemically-selective measurements have been used to evaluate the magnetic properties of the encapsulated NPs. The encapsulated Fe NPs display magnetic remanence up to room temperature, low coercivity, high chemical stability and no significant anisotropy. Our surface-sensitive measurements combined with the specific morphology of the studied VACNTs allow us to pinpoint the contribution of the surface oxidized or hydroxidized iron catalysts present at the VACNT-substrate interface. Element-specific and surface-sensitive measurements provide evidence of magnetic remanence up to room temperature, low coercivity and high stability of 5-10 nm iron metal nanoparticles encapsulated inside the tip of vertically-aligned mm-long carbon nanotubes.