Carbon nanostraws: nanotubes filled with superparamagnetic nanoparticles

Abstract

A two-step magnetically assisted capillary action method is demonstrated as a facile technique to produce hollow carbon nanotubes filled with uniformly dispersed Fe 3 O 4 nanoparticles (NPs). Template-assisted chemical vapor deposition (CVD) grown CNTs with average diameter 200-300 nm and length 5-6 μm were effectively used as 'nanostraws' to suck in chemically synthesized Fe 3 O 4 nanoparticles (mean size ∼6 nm) in a ferrofluid suspension. Temperature and magnetic field-dependent DC magnetization measurements indicate that these functionalized nanotubes are superparamagnetic at room temperature with enhanced interparticle interactions due to the close packing of the nanoparticles within the tubes. Magnetic relaxation phenomena in these filled nanotubes are probed using frequency-dependent AC susceptibility. The reasonably large saturation magnetization (M s = 65 emu g −1 ) attained in these nanostructures makes them very promising for a diverse set of applications that utilize both the magnetic and dielectric functionalities of these composite nanotube materials.

Spin dynamics and criteria for onset of exchange bias in superspin glass Fe/γ-Fe2O3core-shell nanoparticles

“…However, the scenario is quite different for interacting particles with finite size distribution. Recent experiments have shown an increase in temperature along with broadening of the peak of ZFC curve due to enhanced interactions in the nanoparticles 24 . In the present case, there exists irreversibility in the ZFC and FCW curves even at room temperature, which suggests the presence of inter-particle interactions or some particles in the blocked state.…”

Enhanced magnetoimpedance effect in Co-based amorphous ribbons coated with carbon nanotubes

“…6 The alumina templates were etched away, leaving free standing CNTs. The resulting CNTs were between 250 and 300 nm in diameter, on average (see the inset of Fig.…”

“…1 in this figure, the CNTs show a paramagnetic character at room temperature, which agrees with the fact that these CNTs were synthesized by the CVD method without the use of metal catalysts. 6 Keeping this in mind, we investigated the influence of the CNTs on the GMI of the ribbon. Figure 2 shows a 3 D plot for the magnetic field and frequency dependence of the GMI ratio (DZ/Z) for the ribbon sample coated with 10 lL of CNTs.…”

Magnetism of Co<sub>13</sub>-Filled Carbon Nanotubes of Diverse Chiral Symmetry

“…I reported recently on computational results on magnetic properties of putative Co n @C m (n = 5, 13; m = 60, 70 and 80) endohedral metallofullerenes [13,14]. Instead of fullerenes, single-walled nanotubes (SWNTs) may be preferable, because ends of nanotube are open allowing entering the tube [15][16][17]. In this paper, I use the same computational approach as done in [13,14] to study the magnetism of SWNTs with various chirality which were filled by the icosahedral magnetic Co 13 cluster in alternative orientations to the nanotube's channel.…”