Manipulation of Chemically Synthesized FePt Nanoparticles in Water: Core-Shell Silica/FePt Nanocomposites

摘要

The development of uniform nanometer-sized, magnetic particles and their manipulation to form composite materials has been intensively pursued because of their technological and fundamental scientific importance. Preparing, shaping, and improving FePt-based building blocks earns considerable attention due to their special magnetic properties, since L1_0-ordered Fe_xPt_(1-x). alloys with Fe concentrations in the range 0.45 ≤ x ≤ 0.65 represent magnetic materials with one of the highest magnetic anisotropies known in any material. For such materials the superparamagnetic limit has been shown to be extendable to diameters of less than 4 nm. As a consequence, they are of special interest for future ultrahigh-density (10 Tbit/in.) magnetic recording media and high performance permanent magnetic nanocom-posites. Also, by varying the Fe concentration, the magnetic properties of the particles could be tuned from an antiferro-, via a superpara-, to a ferromagnetic state. Fe_xPt_(1-x) nanopar-ticles have also been actively investigated because of their applications in biological processes, for example, in the detection and capture of Gram-negative bacteria. Recently, organically synthesized FePt nanoparticles have been successfully transferred to water by using tetramethylammoni-um hydroxide (TMAOH) as a stabilizer, therefore, facilitating their use in aqueous environments.