Air-stable Co-, Fe-, and Fe/Co-Nanoparticles and Ferrofluids

Abstract

Summary Air-stable Co, Fe, and Fe/Co nanoparticles are accessible by thermolysis of the metal carbonyl precursors in the presence of aluminium alkyls and subsequent “smooth oxidation”. The structure of the particles was investigated by transmission electron microscopy (TEM, HRTEM), X-ray absorption spectroscopy (XAS), X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS), metastable impact electron spectroscopy (MIES), and small-angle neutron scattering (SANS). The peptization of the nanoparticles with suitable surfactants (oleic and lauric acid, sodium dioctylsulfosuccinate (AOT), LP-4 (a fatty acid condensation polymer), and KorantinSH (N-oleyl sarcosine)) yields magnetic fluids dispersed in carrier liquids such as toluene, kerosene, vacuum and mineral oils which are remarkably stable in air under ambient conditions. The resulting magnetic fluids show good magnetic properties. Several methods for the preparation of water-based MF are presented, e.g., formation of surfactant bilayers, using phase transfer agents, or surface modification with L-cysteine ethyl ester. Water-based metallic magnetic fluids have a high potential for a number of technical and biomedical applications. Technical applications of the Co-based ferrofluids in the field of positioning systems and magnetohydrostatic bearings were investigated. The results emphasize the scope of nanoparticulate ferrofluids having a metallic core.

Ferrofluids: Synthetic Strategies, Stabilization, Physicochemical Features, Characterization, and Applications

“…SFFs synthesized using various surfactants, such as Korantin SH (N-oleyl sarcosine, BASF AG), AOT (SERVA2), or LP4 (fatty acid condensation polymer), in combination with various organic media have been reported. [23,125] However, this reduction in the zeta potential is less likely to affect the stability of SFFs. [126] But this is different in the case of electrostatic stabilization, which is elaborated in the next section.…”

Nanoparticles for hyperthermic therapy: synthesis strategies and applications in glioblastoma

“…Behrens et al demonstrated the potential of ferromagnetic cobalt nanoparticles in modulating the permeability of polyelectrolyte microcapsules. 93 In this study, ferromagnetic gold-coated cobalt nanoparticles were embedded inside polymeric walls using the layer-by-layer self-assembly technique. The polymer capsules consisted of eleven layers, with one layer of ferromagnetic goldcoated cobalt nanoparticles and ten layers of polyelectrolyte bilayers.…”

Functionalized, Biocompatible Coating for Superparamagnetic Nanoparticles by Controlled Polymerization of a Thioglycosidic Monomer

“…Although technical ferrofluids possess extraordinary stability, the coating materials and their synthesis strategy cannot be applied to iron oxide nanoparticles in aqueous solution since they are not soluble in water. Examples of frequently used coating materials of technical ferrofluids are fatty acids and polymers, for example, poly(styrene). , To combine the advantages of polymers used in technical ferrofluids (stability) with the requirements of medically applicable magnetic nanoparticles, it is necessary to develop water-soluble, noncytotoxic, polymeric nanoparticle coating materials. In principle, glycopolymers, that is, synthetic polymers carrying pendant sugar moieties, fulfill the above-mentioned requirements.…”