Anisotropic magnetite nanoclusters with enhanced magnetization as an efficient ferrofluid in mass transfer and liquid hyperthermia

Magnetic nanoparticles have wide range of applications in magneto-optics, sensors, magnetic resonance imaging, ferrofluids, magnetic hyperthermia and drug delivery systems. Here, Fe3O4 nanoclusters were prepared through solvothermal method and they were modified by chemisorption of polyFacrylic acid (PAA). The obtained magnetite nanoparticles were characterized by FT-IR, XRD, TGA, TEM and VSM analyses. It was found that they were monodisperse with the size of about 8-10 nm and formed grape-like nanoclusters with uniform size of 70-100 nm. Magnetic properties of Fe3O4@PAA nanoclusters showed that they are superparamagnetic with almost no hysteresis loop. The colloidal dispersion of modified Fe3O4 nanoclusters in water was highly stable until at least 180 days and exhibited no change in its dispersibility. This was confirmed by zeta potential assessment at different pHs and during the time. Then, they were used as ferrofluid for mass transfer and also liquid magnetic hyperthermia by an alternating magnetic field for the heat build-up in a system, and the results showed their reasonable performance. Magnetorheological properties of a 15 wt% dispersion in water were investigated by rotational rheometry under various magnetic fields and they demonstrated reasonable ferrofluid behavior.