Surfactant-free synthesis and magnetic hyperthermia investigation of iron oxide (Fe3O4) nanoparticles at different reaction temperatures

The effect of reaction temperature (TR, ranging from 40 °C to 80 °C) on magnetic hyperthermia measurements was investigated in the surfactant-free co-precipitation synthesis of magnetite (Fe3O4) nanoparticles (NPs). The size, structure and magnetic properties of the synthesized NPs were studied by X-ray diffraction, field-emission scanning electron microscopy (together with energy dispersive spectroscopy), hysteresis loop and first-order reversal curve analyses. The investigations showed that all the NP samples were single domain with a superparamagnetic (SP) feature. After preparing the respective ferrofluids with a concentration of 5 mg/ml (in distilled water medium) acting as nanoheaters, hyperthermia measurements were performed under an alternating magnetic field with a frequency of 400 kHz. It was found that TR = 60 °C resulted in the maximum specific loss power (SLP) value of 181 W/g together with an SP fraction of 82%, being a suitable candidate for use in magnetic hyperthermia. In this case, the resulting saturation magnetization and SP fraction were in the middle of corresponding values obtained from TR = 40 °C and 80 °C. Our results showed that a balance between relatively high saturation magnetization and low coercive field led to the maximum SLP. [Display omitted] •Magnetite NPs were synthesized at 40 °C ≤ TR ≤ 80 °C by a surfactant-free co-precipitation.•Structural, morphological, magnetic and hyperthermia properties were investigated.•FORC analysis revealed SP fractions, ranging between 76% and 86% at TR = 80 and 40 °C.•Maximum SLP was obtained to be 181 W/g for Ms = 42 emu/g and Hc = 2.5 Oe at TR = 60 °C.•Balanced magnetic properties efficiently involved different heating mechanisms.