One-pot synthesis of highly crystallined λ-MnO2 nanodisks assembled from nanoparticles:: Morphology evolutions and phase transitions

Manganese oxides are important materials in many applications. We describe, for the first time, the facile one-pot synthesis of highly crystallined lambda-MnO2 nanodisks assembled from nanoparticles through a novel wet chemical route. Morphology evolutions, magnetic properties, and phase transitions are also studied by transmission electron microscopy, scanning electron rnicroscopy and thermal gravimetric analysis. A mechanism for the formation of the lambda-MnO2 nanodisks as well as their inner structure is proposed based on controlled experiments. The key to the successful preparation of this novel MnO2 nanostructure has been a synergic control of a surfactant, polyvinylpyrrolidone, and a solvent, dimethyl sulfoxide, capable of stabilizing the microreactors and promoting the assembly of manganese nanoparticles.