Synthesis, Morphology, and Magnetic Characterization of Iron Oxide Nanowires and Nanotubes

Abstract

We have explored the synthesis of iron oxide particles, tubes, and fibrils within the pores of nanoporous polycarbonate and alumina membranes. The membranes contain uniformly distributed cylindrical pores with monodispersed diameters (varying between 20 and 200 nm) and thicknesses of 6 and 60 microm, respectively. By hydrolysis and polymerization of iron salts, particles of different sizes and phases were formed in the pores, building iron oxide particle nanowires. Alternatively, by the sol-gel technique, using as reagents metalloorganic compounds, fibrils and tubes of different iron oxide phases were prepared. Structural and morphological investigations performed using scanning electron microscopy and transmission electron microscopy revealed ordered iron oxide particle wires, tubes, and fibrils formed inside the membrane nanopores. Magnetic characterization was accomplished with a vibrating sample magnetometer. Below the blocking temperature (T(B)), the magnetic behavior of the nanowires was governed by dipolar interaction between nearest-neighbor nanoparticles inside the pore, whereas the energy barrier, and therefore the T(B) value, was mainly governed by dipolar interaction between magnetic moments over larger (interpore) distances. As expected, crystalline iron oxide nanotubes exhibited magnetic perpendicular anisotropy due to their magnetocrystalline and shape anisotropy.

Magnetic properties of variable-sized Fe3O4nanoparticles synthesized from non-aqueous homogeneous solutions of polyols

“…For the nanoparticles prepared from neat DEG ( figure 3(a)) and those synthesized from a 1 : 1 mixture of DEG and NMDEA ( figure 3(b)), the ZFC and FC curves, which coincide initially, start to separate and follow different trends as the temperature is decreased from 300 to 5 K. In the FC mode, the magnetization either increases slightly and then levels off ( figure 3(a)) or decreases to eventually reach a plateau ( figure 3(b)), whereas the ZFC magnetization shows a maximum followed by a steady decrease to a value approaching zero in the low temperature region. The shape of the FC curves in the figures 3(a) and (b) is the result of the presence of dipole-dipole interactions between the oleate-capped particles [35,36]. Moreover, the variation of the magnetization in the ZFC and FC modes indicates a superparamagnetic behaviour for the 6.6 and 11.6 nm sized Fe 3 O 4 particles.…”

A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces

“…Iron oxides are also important as pigments, where natural and synthetic pigments are used in the manufacture of red, brown, and black paints or as admixtures, for example in colored glasses [18][19][20]. Other industrial applications of iron oxides are in magnetic devices [21,22], or semiconductors [23], when the iron oxide can be incorporated into the interlayer of layered compounds as semiconductor pillars which show excellent photocatalytic activity. In medical applications, nanoparticulate magnetic and super-paramagnetic iron oxides have been used for drug delivery in the treatment of cancer [24,25].…”

Magnetic transitions in α-Fe2O3 nanowires

“…For instance, T M and T N of polycrystalline hematite nanowires were reported 6,7 to be 80 and 350 K, respectively, much lower than those corresponding to the bulk material. The synthesis and characterization of hematite nanowires have been described in other works [8][9][10][11][12][13] and different values of the Morin temperature have been reported. In the present work, ␣-Fe 2 O 3 nanowires have been grown by a thermal treatment of compressed Fe powder under argon flow.…”