Self-Assembled Ferromagnetic Monodisperse Manganese Oxide Nanoplates Synthesized by a Modified Nonhydrolytic Approach

Single-crystalline and monodisperse manganese oxide (MnO and Mn3O4) nanoplates have been synthesized via a modified nonhydrolytic approach, using manganous acetate as the precursor in oleylamine, and subsequent controlled oxidization with trimethylamine N-oxide. The formation of MnO nanoplates seems a highly kinetics-driven process, which proceeds under a quite high monomer concentration. Along with manipulating the post-treatment procedure and polarity of dispersants, the as-obtained nanoplates are aligned to form self-assembly nanoarrays either in "side-to-side" formation or "face-to-face" formation. Meanwhile, the MnO and Mn3O4 nanoplates display ferromagnetism at low temperatures. The as-obtained Mn3O4 nanoplates exhibit a coercive field of 8.9 kOe at 5 K, significantly higher than those of bulk Mn3O4 and thin films.