Synthesis of Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes from sacrificial Ag nanorod templates.

Our research focuses on the preparation of Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes which have various engineering applications. Hausmannite manganese oxide (Mn3O4) nanotubes were synthesized via a galvanic replacement reaction at mild reaction conditions. The Mn3O4 nanotubes were prepared by solidification of manganese ions on a sacrificial silver nanorod due to the standard reduction potential difference between solid silver and manganese ions. The Mn ions were reduced to solid while the solid Ag rod was oxidized to ions. Ag-Mn3O4 core-shell nanorods and Mn3O4 nanotubes were simply prepared by changing the amount of manganese ions. The Mn3O4 layer in the nanorods and nanotubes had a Hausmannite crystalline structure and showed weak hysteresis of magnetism. This weak magnetism is likely due to the diamagnetic property of silver and multiple magnetic domain of Mn3O4. This simple replacement reaction could be applied to various oxide nanotube fabrications with exact shape control.