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Magnetic nanoparticles have been used in a wide array of industrial and biomedical applications due to their
unique properties at the nanoscale level. They are extensively used in magnetic resonance imaging (MRI), magnetic
hyperthermia treatment, drug delivery, and in assays for biological separations. Furthermore, superparamagnetic
nanoparticles are of large interest for in vivo applications. However, these unmodified nanoparticles aggregate and
consequently lose their superparamagnetic behaviors, due to high surface to volume ratio and strong dipole to dipole
interaction. For these reasons, surface coating is necessary for the enhancement and effectiveness of magnetic
nanoparticles to be used in various applications. In addition to providing increased stability to the nanoparticles in
different solvents or media, stabilizers such as surfactants, organic/inorganic molecules, polymer and co-polymers
are employed as surface coatings, which yield magnetically responsive systems. In this work we present the
synthesis and magnetic characterization of Fe3O4 nanoparticles coated with 3-aminopropyltriethoxy silane (APS)
and citric acid. The particles magnetic hysteresis was measured by a superconducting quantum interference device
(SQUID) magnetometer with an in-plane magnetic field. The uncoated and coated magnetic nanoparticles were
characterized by using fourier transform infrared (FTIR), UV-vis, X-ray diffraction, transmission electron
microscopy, and thermo-gravimetric analysis.
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