Magnetic Nanoparticles-Based Coated Materials

In the past few decades, nanostructured metallic alloys and metal oxides magnetic materials have been investigated and practiced for various applications. The applicability of these coated nanoparticles (NPs) in magnetic, catalysis, and biomedical fields is possible due to their availability in nano-scale sizes (10–30 nm), high surface-to-volume ratios, controlled magnetic properties, biocompatibility, and capability of further surface functionalization. This chapter specifically focused on surface functionalized cobalt-based nanomaterials, such as Co, Co–Fe alloys, Co–Ni alloys, Co–Pt alloys, and cobalt ferrite (CoFe2O4) based coated particles for potential applications. However, challenges for these materials to be used for the above applications remain in their stability at the nano-scale, nontoxic synthesis methods, control of size, dispersion in an aqueous medium, biocompatible surfaces, etc. Therefore, we have described the synthesis of Co-based metal/alloy nanomaterials via aqueous/organic mediated chemical reduction routes using NaBH4, Li(Et)3BH (superhydride), polyol as reducing agents and stabilized via coating surfaces with various capping agents, e.g., polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), oleic acid, oleyl amine, mesoporous silica, etc. The presence of Co2+ ions in CoFe2O4 NPs renders cytotoxic effects to some extent to the cells in its vicinity. Therefore, in this chapter pure and doped CoFe2O4-based coated magnetic materials coated with organic (e.g., using folic acid, oleic acid long chain acids, etc.) or biomaterials (e.g., hydroxyapatite, bio-polymers, and silica, etc.) will be described. Apart from synthesis, the scope of the chapter also includes materials characterization and magnetic properties studies. In the characterizations, crystal structure, phase purity, and crystallite sizes can be obtained by X-ray diffraction studies. Particle sizes and surface morphology are studied with electron microscopes (SEM and TEM). Elemental composition studies can be performed from SEM–EDX or ICP AES. The surface structure of the coated particles can be studied from FTIR and XPS spectroscopy. Magnetic hysteresis (M vs. H) and temperature dependent magnetization (M vs. T) at low temperature will be described. In this chapter, we have summarized the synthesis and functionalization of Co-based nanomaterials for various applications in coated form so that they can be put into the practice in future.