In situ preparation of nanocrystalline gamma-Fe2O3 in iron(II) cross-linked alginate gels

The cross-linking agent, iron(II), used to bind a linear polysaccharide, alginic acid, was used as the reaction center for the in situ formation of nanocrystalline iron oxides. The resulting hydrogel was isolated in the form of spherical beads ca. 2 mm in diameter that are superparamagnetic and stable indefinitely at room temperature. The dehydrated beads contain from 10 to 50% iron predominantly in the farm of maghemite, gamma-Fe2O3, nanoparticles 4-15 nm in diameter.