Chemical Transformation of Colloidal Nanostructures with Morphological Preservation by Surface-Protection with Capping Ligands.

When nanocrystals are made to undergo chemical transformations, there are often accompanying large mechanical deformations and changes to overall particle morphology. These effects can constrain development of multistep synthetic methods through loss of well-defined particle morphology and functionality. Here, we demonstrate a surface protection strategy for solution phase chemical conversion of colloidal nanostructures that allows for preservation of overall particle morphology despite large volume changes. Specifically, via stabilization with strong coordinating capping ligands, we demonstrate the effectiveness of this method by transforming β-FeOOH nanorods into magnetic Fe3O4 nanorods, which are known to be difficult to produce directly. The surface-protected conversion strategy is believed to represent a general self-templating method for nanocrystal synthesis, as confirmed by applying it to the chemical conversion of nanostructures of other morphologies (spheres, rods, cubes, and plates) and compositions (hydroxides, oxides, and metal organic frameworks).