Non-native transition metal monoxide nanostructures: unique physicochemical properties and phase transformations of CoO, MnO and ZnO

The discovery of unprecedented, non-native phases of transition metal oxides is a fascinating theme in materials chemistry, including the development of new synthetic strategies with excellent sizeand phase-selectivity, and elucidation of their unique physicochemical properties. Most of the first-row transition metal monoxides, such as MnO, FeO, CoO and NiO, are known to exist in a cubic phase, but only ZnO adopts a hexagonal structure. This review summarizes recent results on the syntheses and characterization of the non-native phases of h-CoO, h-MnO and c-ZnO transition metal monoxides, compared to their native phases. The investigation of the sizeand phase-selective synthetic methods, formation mechanism and unique physicochemical properties of non-native transition metal monoxides would have an enormous impact on materials chemistry and open a promising avenue for magnetic, electronic and spintronic applications. NPG Asia Materials (2017) 9, e364; doi:10.1038/am.2017.38; published online 24 March 2017