Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.
This paper describes a sol−gel approach for the coating of superparamagnetic iron oxide nanoparticles with uniform shells of amorphous silica. The coating process has been successfully applied to particles contained in a commercial ferrofluid (e.g., the EMG 304 of Ferrofluidics) and those synthesized through a wet chemical process. The thickness of silica coating could be conveniently controlled in the range of 2−100 nm by changing the concentration of the sol−gel solution. Fluorescent dyes, for example, 7-(dimethylamino)-4-methylcoumarin-3-isothiocyanate (DACITC) and tetramethylrhodamine-5-isothiocyanate (5-TRITC), have also been incorporated into the silica shells by covalently coupling these organic compounds with the sol−gel precursor. These multifunctional nanoparticles are potentially useful in a number of areas because they can be simultaneously manipulated with an externally applied magnetic field and characterized in situ using conventional fluorescence microscopy.
in the Sonochemical Synthesis of Gamma Iron Oxide and its ..
Oil-soluble type functionalization employed in order to prevent or decrease the agglomeration of iron oxide NPs and increase the stability give rise to the monodispersity, for instance, iron oxide NPs frequently dispersed in long-chain substance of hexadecane, the classic example being oleic acid (CH3(CH2)7CH=CH(CH2)7CO2H), which has a C18 tail with a cis-double-bond in the middle, forming a kink. Such kinks have been postulated as necessary for effective stabilization, and indeed stearic acid (CH3(CH2)16CO2H) with no double-bond in its C18 tail, cannot stabilize the iron oxide NPs [,-]. Additionally, Oleic acid is widely used in ferrite nanoparticle synthesis because it can form a dense protective monolayer, thereby producing highly uniform and monodisperse particles. However, relative to the naked iron oxide NPs, the average diameter of functionalized NPs will increase in the range of 0–5 nm, and its saturation magnetization (MS) almost unchanged.