Single-Crystalline MFe₂O₄ Nanotubes/Nanorings Synthesized by Thermal Transformation Process for Biological Applications

Abstract

We report a general thermal transformation approach to synthesize single-crystalline magnetic transition metal oxides nanotubes/nanorings including magnetite Fe(3)O(4), maghematite gamma-Fe(2)O(3), and ferrites MFe(2)O(4) (M = Co, Mn, Ni, Cu) using hematite alpha-Fe(2)O(3) nanotubes/nanorings template. While the straightforward reduction or reduction-oxides process was employed to produce Fe(3)O(4) and gamma-Fe(2)O(3), the alpha-Fe(2)O(3)/M(OH)(2) core/shell nanostructure was used as precursor to prepare MFe(2)O(4) nanotubes via MFe(2)O(4-x) (0 < x < 1) intermediate. The transformed ferrites nanocrystals retain the hollow structure and single-crystalline nature of the original templates. However, the crystallographic orientation-relationships of cubic spinel ferrites and trigonal hematite show strong correlation with their morpologies. The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties. Moreover, they have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells, suggesting that these biocompatible magnetic nanotubes/nanorings have great potential in biomedicine and biomagnetic applications.

Fabrication and magnetic properties of NiFe2O4 nanofibers obtained by electrospinning

“…These properties have attracted attention for high performance applications in catalysis, magnetic fluids, magnetic drug delivery, microwave industries, spintronics, electrical devices, etc. [1][2][3][4]. Among these, nickel ferrite (NiFe 2 O 4 ) of inverse spinel structure is an interesting one due to the unique distribution of all Ni 2+ ions at the B sites (octahedral) and equally of Fe 3+ ions at both A (tetrahedral) and B sites.…”

Magnetic field induced controllable self-assembly of maghemite nanocrystals: From 3D arrays to 1D nanochains

“…The preparation of ordered magnetic nanostructures is usually achieved via template-assistant strategies [5][6][7]. Such strategies rely on additional steps to fabricate the template, which is usually complex, time-consuming, and expensive, thus may not be used for large-scale preparation.…”

Hydrothermal synthesis of α-Fe2O3 nanorings with the help of divalent metal cations, Mn2+, Cu2+, Zn2+ and Ni2+

“…doi:10.1016/j.molstruc.2010.12.063 sized spindle-shape a-Fe 2 O 3 particles by hydrogen gas. Fan et al [14] modified the Jia's procedure [8] to synthesize ferrite MFe 2 O 4 (M = Co, Mn, Ni, Cu) nanotubes. Hu et al [15] modified the Jia's procedure [8] by introducing microwave radiation in the hydrothermal process.…”