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We present a combined experimental and theoretical study dedicated to analyze the human myeloperoxidase (h-MPO)-catalyzed degradation of oxidized nitrogen-doped multi-walled carbon nanotubes (NMWCNTs-Ox) in vitro at 27 °C. NMWCNTs are synthesized by the aerosol assisted chemical vapor deposition (AACVD) technique and are characterized by employing transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), as well as Raman and X-ray photoelectron spectroscopies. H-MPO degradation, involving hypochlorous acid and hypochlorite species, leads to complete removal of CNTs with diameters smaller than 75 nm from the samples. Simultaneously, for larger sizes, it produces the formation of highly deformed NMWCNTs decorated with NaCl nanoparticles, which exhibit reduced cytotoxicity in exposed monocytes studies compared with the initial nanotube samples. Density functional theory (DFT) calculations performed on model nitrogen-doped CNTs are also presented to explore, at an atomistic level, the fundamental aspects underlying degradation. Our DFT results reveal that reactivity of carbon walls is significantly affected around N-doped pyridinic, pyrrolic, and substitutional sites, leading to the existence of HClO molecules physisorbed close to those defects and high local concentrations of chemisorbed ClO species on C atoms adjacent to the N-rich regions. The formation of these hypochlorite molecular islands on the nanotube surface facilitates ClO dissociation producing strongly bound O species and Cl atoms that can be carbon bonded or released into the environment. The previous surface reaction results in the cleavage of the underlying C–C bonds, creating holey regions on the graphitic walls. The continuation of this process would lead to the formation of larger holes on the nanotube surface, allowing, on the one hand, the permeation of ClO molecules to the internal layers and, on the other hand, producing a reduction of the NMWCNTs diameter as observed from our experimental data. Image 1 [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate that it is possible to encapsulate ferromagnetic nanowires of Fe, FeCo and FeNi inside carbon nanotubes via chemical vapor deposition methods. These wires exhibit extremely high coercive fields when compared with the bulk phases. We review the state-of-the art characterization carried out on these novel wires and discuss the importance of having aligned arrays of carbon nanotubes filled with ferromagnetic materials, towards the development of novel magnetic storage devices. In this context, we will show from the experimental and theoretical stand points, that the wire shape, aspect ratio and inter-wire distances play a crucial role in the fabrication of novel storage components. In addition, we theoretically show that pure carbon nanostructures such as carbon nanotori, perforated fullerenes and nanoporous graphitic structures, exhibiting negative Gaussian curvature introduced by the presence of non-hexagonal rings, behave as strong paramagnets experiencing large magnetic moments when an external magnetic field is applied. The latter results could explain some of the magnetic properties observed experimentally in carbon nanofoams and polymerized C60 phases. We envisage that magnetism in different families of nanostructures will be playing a key role in the development of emerging technologies in the present century. [Copyright &y& Elsevier]

More than ten years ago, it was suggested theoretically that boron nitride (BN) nanotubes could be produced. Soon after, various reports on their synthesis appeared and a new area of nanotube science was born. This review aims to cover the latest advances related to the synthesis of BN nanotubes. We show that these tubes can now be produced in larger amounts and, in particular, that the chemistry of BN tubes appears to be very important to the production of reinforced composites with insulating characteristics. From the theoretical standpoint, we also show that (BN)-C heteronanotubes could have important implications for nanoelectronics. We believe that BN nanotubes (pure and doped) could be used in the fabrication of novel devices in which pure carbon nanotubes do not perform very efficiently. [Copyright &y& Elsevier]