Synthesis of Ag-Mn ₃O ₄ core-shell nanorods and Mn ₃O ₄ nanotubes from sacrificial Ag nanorod templates

Our research focuses on the preparation of Ag-Mn ₃O ₄ core-shell nanorods and Mn ₃O ₄ nanotubes which have various engineering applications. Hausmannite manganese oxide (Mn ₃O ₄) nanotubes were synthesized via a galvanic replacement reaction at mild reaction conditions. The Mn ₃O ₄ 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-Mn ₃O ₄ core-shell nanorods and Mn ₃O ₄ nanotubes were simply prepared by changing the amount of manganese ions. The Mn ₃O ₄ 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 Mn ₃O ₄. This simple replacement reaction could be applied to various oxide nanotube fabrications with exact shape control.