One-step synthesis of highly water-dispersible Mn3O4 nanocrystals

Highly water-dispersible Mn3O4 nanocrystals with well-controlled size, size distribution and high crystallinity have been successfully synthesized through a modified polyol process. Poly(acrylic acid) is used as the capping agent, conferring upon the particles high water-dispersion, of which the carboxylate groups partially bind to the nanocrystal surface and the uncoordinated carboxylate groups extend into water. The water-dispersible Mn3O4 nanocrystals can be further transferred to nonpolar solvent by linking oleylamine molecules through electrostatic interaction. The as-prepared Mn3O4 nanocrystals exhibit ferromagnetic behavior at low temperature and weak paramagnetic behavior at room temperature. The Curie-Weiss temperature and the blocking temperature are 40 K and 32 K, respectively.