Synthesis of monodisperse nanocrystals of manganese oxides

We report a simple and effective method for the generation of high-quality nanocrystals of manganese oxide, MnO, with an alkyl capping group. MnO is a model system for the theoretical study of electronic and magnetic properties of rock salt oxides. Synthesis of relatively monodisperse nanocrystals of MnO was achieved over a range of sizes between 7 and 20 nm. The nanocrystals are readily dispersed in nonpolar solvents, and their uniformity allows for the formation of superlattices, as observed by TEM. Fitting size evolution/time data with the Lifshitz-Slyozov-Wagner model indicates that the increase in particle size from 7 nm is dominated by diffusion-limited growth. Controlled chemical oxidation can allow for the preparation of nanocrystals of Mn3O4 from MnO. We demonstrate the use of acetate precursors in the preparation of ligand-capped, transition metal oxide nanocrystals (of MnO and FeO), which are safer and more environmentally benign than their metal carbonyl counterparts.