Microwave-Assisted Synthesis of Water-Dispersible Humate-Coated Magnetite Nanoparticles: Relation of Coating Process Parameters to the Properties of Nanoparticles

Nowadays, there is a demand in the production of nontoxic multifunctional magnetic materials possessing both high colloidal stability in water solutions and high magnetization. In this work, a series of water-dispersible natural humate-polyanion coated superparamagnetic magnetite nanoparticles has been synthesized via microwave-assisted synthesis without the use of inert atmosphere. An impact of a biocompatible humate-anion as a coating agent on the structural and physical properties of nanoparticles has been established. The injection of humate-polyanion at various synthesis stages leads to differences in the physical properties of the obtained nanomaterials. Depending on the synthesis protocol, nanoparticles are characterized by improved monodispersity, smaller crystallite and grain size (up to 8.2 nm), a shift in the point of zero charge (6.4 pH), enhanced colloidal stability in model solutions, and enhanced magnetization (80 emu g(−1)).