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Updated: Jun 18, 2026

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition
Published on: February 5, 2022
Optimized steric stabilization of aqueous ferrofluids and magnetic nanoparticles
Nirmesh Jain1, Yanjun Wang, Stephen K Jones
1School of Chemistry and Key Centre for Polymers and Colloids, The University of Sydney, NSW 2006, Australia.
Abstract:
The preparation and properties of an aqueous ferrofluid consisting of a concentrated (>65 wt %) dispersion of sterically stabilized superparamagnetic, iron oxide (maghemite) nanoparticles stable for several months at high ionic strength and over a broad pH range is described. The 6-8 nm diameter nanoparticles are individually coated with a short poly(acrylic acid)-b-poly(acrylamide) copolymer, designed to form the thinnest possible steric stabilizing layer while remaining strongly attached to the iron oxide surface over a wide range of nanoparticle concentrations. Thermogravimetric analysis yields an iron oxide content of 76 wt % in the dried particles, consistent with a dry polymer coating of approximately 1 nm in thickness, while the poly(acrylamide) chain length indicated by electrospray mass spectrometry is consistent with the 4-5 nm increase in the hydrodynamic radius observed by light scattering when the poly(acrylamide) stabilizing chains are solvated. Saturation magnetization experiments indicate nonmagnetic surface layers resulting from the strong chemical attachment of the poly(acrylic acid) block to the particle surface, also observed by Fourier transform infrared spectroscopy.
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