Symbiosis of Silica Biomorphs and Magnetite Mesocrystals

Abstract

Silica biomorphs are extraordinary inorganic superstructures formed via autocatalytic co‐precipitation and bottom‐up self‐assembly of alkaline‐earth carbonates and silica. However, they show no inherent functionality except for their striking textural motifs and curved morphologies. This work presents strategies to magnetize silica biomorphs, thus creating thermally stable ceramic microswimmers with unique elaborate shapes. This is achieved by growing super paramagnetic magnetite mesocrystals on and around the complex curved surfaces of biomorphs, while keeping their morphology and maintaining mesocrystal integrity. Selective mesocrystal formation on certain parts of the substrates is induced by chemical modification of the biomorph surface, increasing the loading of magnetite on the silica–carbonate structures and, in suitable cases, rendering them able to respond to external magnetic fields and move as microswimmer entities. In this way, the complex ultrastructure of silica biomorphs is successfully used as a template for functional ceramics. Furthermore, selective dissolution of the carbonate core from the biomorphs leads to hollow magnetic structures that could be filled with actives, thus serving as microcarriers with considerable loading capacity.