In-situ precipitation of ultra-stable nano-magnetite slurry

• Ultra-stable aqueous colloidal suspension of nano-magnetite was prepared.
• Different concentrations of dodecanoic acid were used as surfactant.
• Addition of surfactant led to polysidpersity reduction and stability in a wide range of pH.
• Magnetite nanoparticles dispersed in water show superparamagnetic behavior and saturation magnetization as high as 8.6 emu g−1.
• The optimum amount of saturated fatty acid to prepare highly-dispersed nano-magnetic slurry is 4.5 g.

In this contribution, we prepared water-based magnetic fluids of iron oxide nanoparticles using an in-situ precipitation method. The effect of dodecanoic acid addition as a surfactant on the physico-chemical and magnetic properties of iron oxide nanoparticles was investigated as well. The quantity of the surfactant was varied between 3 and 5 g. Raman spectroscopy and X-ray diffraction (XRD) were utilized to confirm the presence of spinel phase magnetites (Fe3O4). Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize the resulting magnetic nanoparticles' size and morphology. The results showed polydispersed hexagonal nanoparticles (average diameter of ca. 70 nm) as a result of the protocol. Moreover, the pH-dependent stability of the samples confirms that magnetite nanofluids were highly stable in the wide range of pH, from 4–12. The optimal amount of dodecanoic acid to produce ultra-stable nano-magnetite slurry with the highest saturation magnetization of 8.6 emu g−1 was determined to be 4.5 g.

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