Effect of synthesis conditions on the properties of citric-acid coated iron oxide nanoparticles

Citric acid is a widely accepted coating material in nanoparticle fabrication for biomedical applications while iron oxide is one popular magnetic material with excellent properties for use in nanoparticle form. However, the effect of synthesis conditions on the properties of iron oxide nanoparticles is not sufficiently understood. Here, citric-acid coated iron oxide nanoparticles were synthesized based on the co-precipitation method through both one-step and two-step process, respectively. The citric acid was added at different stages, and various coating temperatures were used in the two-step process. The nanoparticles were characterized by multiple techniques including Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and vibrating sample magnetometry. It was found that the addition of citric acid at different stages can alter the nanoparticle core size, while the coating temperature affects citric acid adsorption around nanoparticles surface and alters the nanoparticle hydrodynamic size. The effect of citric-acid coating on the magnetic behavior was also investigated on 9 nm and 25 nm iron oxide nanoparticles.

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► Addition of citric acid at different stages could adjust nanoparticles core sizes.
► Coating temperature could affect the citric acid adsorption around nanoparticles.
► Citric-acid coating did not affect superparamagnetic feature of small sized IONPs.
► Citric-acid coating decreased coercivity of larger sized IONPs with coercivity.