One-Pot Synthesis and Morphology Control of Spinel Ferrite (MFe₂O₄, M = Mn, Fe, and Co) Nanocrystals from Homo- and Heterotrimetallic Clusters

One-pot syntheses of size- and shape-controlled spinel ferrite, MFe₂O₄ (M = Fe, Co, and Mn), nanocrystals (NCs) larger than 20 nm in size are achieved by the thermolysis of mixed-valence triiron complexes and heterotrimetallic complexes as a precursor using benzilic acid (BA) as a capping ligand. The molar ratio of BA toward the precursor complexes plays a critical role in determining the morphology of the NCs. With the increase of BA concentration, the morphology of the Fe₃O₄ NCs changed from truncated-octahedron to cube. The magnetic properties of the ferrite NCs obtained by the use of BA as template molecules were ferrimagnetic behavior at room temperature.