Three‐Dimensional Assemblies of Zirconia Nanocrystals Via Shape‐Preserving Reactive Conversion of Diatom Microshells

The synthesis of three‐dimensional (3‐D) assemblies of zirconia nanocrystals via the shape‐preserving reactive conversion of biologically reproducible, silica‐based microtemplates (diatom microshells) is demonstrated for the first time. Silica diatom microshells were first converted into magnesia replicas via an oxidation–reduction displacement reaction with magnesium gas. The magnesia replicas were then converted into zirconia replicas via a metathetic displacement reaction with zirconium tetrachloride gas. By utilizing both types of shape‐preserving displacement reactions, bioclastic silica microtemplates may be converted into functional nanocrystalline assemblies with a variety of complex, but well‐controlled 3‐D shapes and chemistries for catalytic/chemical, biological, electrical, thermal, mechanical, and other applications.