Synthesis of monodisperse MFe2O4 (M = Fe and Zn) nanoparticles for polydiethylsiloxane-based ferrofluid with a solvothermal method

• MFe2O4 nanoparticles were synthesized through a facile solvothermal method.
• The relationship between viscosity and temperature of the polydiethylsiloxane-based ferrofluid is discussed.
• Fe3O4 nanoparticles have a saturation magnetization of 73.06 emu/g at room temperature.

Monodisperse MFe2O4 (M = Fe, Zn) nanoparticles were successfully synthesized for the application of polydiethylsiloxane-based (PDES) ferrofluids (FFs) via a novel solvothermal method, with which 1-octanol and 1-octanamine act as binary solvent, oleic acid (OA) as the surfactant and metal acetylacetonate [M(acac)3](M = Fe and Zn) as the metal source. X-ray diffractometer confirms that the resultant nanoparticles are pure MFe2O4 with a spinel structure. Infrared spectroscopy indicates that oleic acid is bound to the surface of MFe2O4 through a covalent bond between carboxylate (COO−) and metal cations. The ratio of 1-octanol and 1-octanamine plays a key role in the formation of the sphere-shaped morphology. Transmission electron microscopy (TEM) images confirm that the Fe3O4 particles are of 4–11 nm with good monodispersity and a narrow size distribution. The saturation magnetization of Fe3O4 nanoparticles with sizes of 7 nm can reach up to 73.06 emu/g. Polydiethylsiloxane-based (PDES) FFs show relatively smaller changes of the viscosity with low temperatures (from −7 to 20 °C) than the polydimethylsiloxane-based (PDMS) FFs. For FFs applications, the relationship between viscosity and temperature is also discussed.

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