Hydrothermal synthesis of superparamagnetic Fe₃O₄ nanoparticles with ionic liquids as stabilizer

Highlights: • Superparamagnetic Fe₃O₄ nanoparticles with good dispersity have been synthesized via hydrothermal method. • Ionic liquid [C₁₆mim]Cl acts as stabilizer for the Fe₃O₄ nanoparticles. • Fe₃O₄ nanoparticles have a saturation magnetization of 67.69 emu/g at 300 K. - Abstract: Superparamagnetic Fe₃O₄ nanoparticles have been successfully synthesized under hydrothermal condition with the assistant of ionic liquid 1-hexadecyl-3-methylimidazolium chloride ([C₁₆mim]Cl). The structure and morphology of the sample have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM), and the results indicate that the as-synthesized inverse spinel Fe₃O₄ nanoparticles have an average diameter of about 10 nm and exhibit relatively good dispersity. More importantly, it is found that [C₁₆mim]Cl acts as stabilizer for the Fe₃O₄ nanoparticles by adsorbing on the particles surfaces to prevent the agglomeration. In addition, the obtained superparamagnetic Fe₃O₄ nanoparticles have a saturation magnetization of 67.69 emu/g at 300 K