Synthesis of a magneto-chromatic tunable Fe3O4-HPAM colloid

Abstract

Colloids of soft magnetic (Fe3O4) submicrometer particles, formed by magnetic nanoparticle clusters, coated with a polyelectrolyte (hydrolyzed polyacrylamide; HPAM) were fabricated successfully in situ with a highly controllable chemical approach. The formation mechanism of submicron particles was analyzed under the amounts of HPAM, urea, citrate, and metallic precursors. This mechanism was followed by SEM. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The results showed that the physicochemical properties of the HPAM favored physical interactions with the reactants, promoting the formation of dense-packed magnetic micrometer clusters in one-step synthesis. The different estimated radii of these particles in solution (hydrodynamic and gyration) and dried (internal radius) decrease when the HPAM amount increases. Moreover, the particles exhibited a superparamagnetic behavior with a magnetization of 48.2 emu/g, 50.3 emu/g, and 54.3 emu/g when the amounts were 0.5 g, 1 g, and 2g of HPAM, respectively. Consequently, the optical response of the colloids to the application of a rotating magnetic field (RMF) parallel to the horizontal plane where they were located exhibited a behavior similar to photonic structures since their reflection spectrum showed a periodic diffraction color that closely matches the frequency of the RMF.