Well Shaped Mn3O4 Nano‐octahedra with Anomalous Magnetic Behavior and Enhanced Photodecomposition Properties

Abstract Very uniform and well shaped Mn 3 O 4 nano‐octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape‐directing agent. The nano‐octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano‐octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn 3 O 4 nano‐octahedra exhibit anomalous magnetic properties: the Mn 3 O 4 nano‐octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn 3 O 4 nanoparticles with 10 nm size because of the vertical axis of [001] plane and the exposed {101} facets. With these Mn 3 O 4 nano‐octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn 3 O 4 nano‐octahedra is much superior to that of commercial Mn 3 O 4 powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn 3 O 4 nano‐octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn 3 O 4 nano‐octahedra.