Biomedical Engineering Reference
In-Depth Information
13
Approaches to the Synthesis and Characterization of Spherical
and Anisotropic Magnetic Alloy Nanomaterials
Matthew S. Wellons and Charles M. Lukehart
13.1
Introduction
Compared to top-down plasma or sputter-deposition methods, bottom-up chemi-
cal synthesis and self-assembly approaches offer more fl exibility in creating mag-
netic alloy nanoparticles of controlled size, shape, composition, and physical
properties. This chapter provides a summary of the latest developments in the
chemical synthesis of spherical and anisotropic transition metal alloy magnetic
nanoparticles, with an emphasis on how synthesis conditions impact nanoparticle
shape and composition. The methods used to prepare anisotropic magnetic alloy
nanoparticles represent an emerging area of high research interest, and an over-
view of recent advances in this area over the past two years is included. Recent
developments in the synthesis of ferromagnetic and superparamagnetic M
−
Pt
(M
Ni, Fe, Co) noble metal alloy nanoparticles are fi rst reviewed, refl ecting the
current high interest in the formation of strongly ferromagnetic nanoparticles. A
summary of synthesis strategies for preparing magnetically soft binary alloy
nanoparticles of the early transition elements Co, Ni, and Fe follows. Other mag-
netic nanoparticle reviews are available [1 - 7] , focusing on biomedical applications
[1, 2] , L
1
0 metal alloys [3, 7], multicomponent heterostructured compositions [5],
or broader coverage of magnetic particle synthesis, magnetic properties, and appli-
cations to catalysis and biotechnology [4, 6].
The controlled synthesis and assembly of magnetic nanoparticles has attracted
much interest for applications in biomedicine [1, 2] , in high - density magnetic
recording, high-sensitivity magnetic sensors, and advanced nanocomposite per-
manent magnets [3-5]. Magnetic alloy nanoparticles have been synthesized by
several different methods, including:
•
Molecular precursor(s) thermal decomposition in organic or aqueous solvents,
often coupled with the chemical reduction of metal ions.
•
Microemulsion strategies coupled with chemical reduction.
•
Pyrolysis of metal - organic polymers, which serve as single - source precursors
for desired metal alloys.
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