Functional Spinel Oxide Nanomaterials: Tailored Synthesis and Applications

Metal oxides of the spinel crystal structure, with structural formula AB 2 O 4, have been studied for decades due to their utility in applications such as catalysis, energy storage, magnetism, optics, and electronics. Here, we provide a comprehensive view of developments in the synthesis and main applications of spinel oxide nanomaterials over the past few years. We classify synthesis strategies as vapor-, solution-, or solid-phase methods and discuss their relative advantages and disadvantages. Then, we consider how structure and composition affect the properties and applications of spinel nanomaterials. For structure effects, nanomaterials with 1D, 2D, and 3D morphologies are examined to illustrate the relationships between shape, properties, and applications. With respect to composition, the most common families of spinels, MFe 2 O 4, MCo 2 O 4, and MMn 2 O 4, are introduced to illustrate the similarities and differences in properties within and between these groups of materials. Finally, we discuss the main applications of all types of spinels including electromagnetic devices, electrocatalysis, batteries, solar cells, and sensors, and we consider the remaining challenges and the future outlook for this class of nanomaterials.