Synthesis and Ligand Exchange of Monodisperse Manganese Oxide Nanoparticles

Abstract

Uniform-sized manganese oxide (Mn3O4) nanoparticles were synthesized via the sol-gel process. After applying a ligand exchange process, they were transferred from a nonpolar organic solvent into a polar hydrophilic solvent to form a highly stable dispersion. The synthetic process is very simple, cost-effective, and easy to scale up. Mn3O4 nanoparticles were synthesized via reaction of manganese(II) acetate tetrahydrate with water in xylene, in the presence of oleic acid and oleylamine as surfactants. Synthesized Mn3O4 nanoparticles have a square plate shape, and the crystal structure of hausmannite. Nitrosonium tetrafluoroborate (NOBF4) was used to replace the original organic surfactants on the surface of the nanoparticles, and to stabilize the nanoparticles in the polar hydrophilic solvents. TEM, XRD, FTIR, DLS, and TGA analysis were performed to confirm the effect of the process and to investigate the mechanism. This work provides a potential route to synthesize manganese oxide nanoparticles on a large scale and preconditioning process for industrial applications.