Polymer-assisted size control of water-dispersible iron oxide nanoparticles in range between 15 and 100 nm

• Coated Fe3O4 nanoparticles were synthesized by the precipitation oxidation method.
• Starch can be employed as an effective control agent to tune the nanoparticle size.
• Starch coated nanoparticles are water dispersible and forms a ferrofluid.
• Nature of the employed polymer defines the efficiency of the size-control process.

Starch-coated Fe3O4 nanoparticles were synthesized by the precipitation–oxidation of ferrous hydroxide method. Starch was employed as a kinetic control agent, and the effect of the polymer on both size and aggregation of the Fe3O4 nanoparticles was studied. The size of the as-prepared magnetite nanoparticles was tuned from 15 to 100 nm by changing the time of addition of a starch solution on the reaction system. Also, the starch-coating over Fe3O4 nanoparticles assures good water-dispersibility, stability, and possible biocompatibility. Transmission and scanning electron microscopies (TEM, SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and magnetic measurements were used to characterize the prepared samples.Kinetic control assays were also done with polyethylene glycol and polyvinyl alcohol in order to study the influence of the polymer nature in the size and aggregation process of the Fe3O4 nanoparticles. For this work, the effect is more pronounced for voluminous polymers, with large electrosteric hindrance produced by increased polar groups per monomer, like starch.

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