Tuning Specific Loss Power of CoFe2O4 Nanoparticles by Changing Surfactant Concentration in a Combined Co-Precipitation and Thermal Decomposition Method

New synthetic approaches of nanoparticles (NPs) can be used for magnetic hyperthermia, destroying malignant cells without damaging healthy tissues. Here, a combination of co-precipitation and thermal decomposition techniques was employed to synthesize monodisperse CoFe2O4 NPs. A mixture of oleylamine and oleic acid with different concentrations was utilized as a surfactant, significantly changing magnetic, morphological and structural properties of the NPs. Increasing the surfactant concentration from 1 to 7.5 mmol resulted in maximum and minimum coercivity and saturation magnetization of 420.0 Oe 73.6 emu/g, and 67.2 Oe and 48.3 emu/g, respectively, arising from the prevention of agglomeration and reduction in crystallite size. The first-order reversal curve analysis was employed to clarify the role of the surfactant in magnetic distributions and detailed characteristics. The specific loss power of the NPs was found to be tuned for the different surfactant concentrations, achieving a maximum of 268.5 W/g at 7.5 mmol for CoFe2O4 NPs with enhanced superparamagnetic contribution in Néel and Brownian mechanisms. MTT assay of the NPs was also carried out, indicating their low cytotoxicity.