A comparative study on characterization and hyperthermia properties of CoFe2O4 nanoparticles synthesized with different surfactants

The type of surface active agent (surfactant) has been known to significantly influence chemical and physical properties of ferrite nanoparticles (FNPs). Nevertheless, no comparison has been made so far between the surfactant type and hyperthermia properties of cobalt FNPs. Here, by using a co-precipitation approach, CoFe2O4 FNPs are synthesized in the absence (free) and presence of different surfactants such as cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyvinylpyrrolidone (PVP). The use of surfactant causes FNP size to be reduced in such a way that it decreases coercivity and enhances superparamagnetic contribution significantly, making CoFe2O4 FNPs suitable for magnetic hyperthermia applications. First-order reversal curve (FORC) analysis indicates that the free surfactant synthesis leads to a mixture of single domain and superparamagnetic FNPs, whereas the PVP surfactant reduces the formation of single domain FNPs with less uniformity. For hyperthermia measurements, ferrofluids of the FNPs with different concentrations (0.5-6 mg mL(-1)) are prepared and examined under a frequency of 400 kHz and magnetic field intensities in the range between 100 and 400 Oe. The maximum specific absorption rate (SAR) value is obtained to be 781 W g(-1) for FNPs synthesized using PVP surfactant.