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Ligand-Assisted Solid-State Transformation of Nanoparticles

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journal contribution
posted on 2020-03-23, 12:48 authored by Bo Li, Jinxing Chen, Lili Han, Yaocai Bai, Qingsong Fan, Chaolumen Wu, Xiaojing Wang, Michael Lee, Huolin L. Xin, Zhiwu Han, Yadong Yin
Thermal treatment is generally a desirable process to improve the properties of nanomaterials, which however often leads to undesirable problems such as aggregation and shape deformation. Here, we overcome this challenge by developing a ligand-assisted calcination strategy for shape-preserved chemical transformation of nanostructures. While capping ligands are often thought to be effective in solution phase synthesis, we show that their presence during high-temperature calcination not only maintains the overall particle morphology but also offers the possibility of effective creation of controllable porosity in metal oxide nanostructures. We demonstrate a particularly elegant example of this strategy, which involves the chemical conversion of β-FeOOH ellipsoids into porous α-Fe2O3 and magnetic Fe3O4 ellipsoids with morphological preservation and excellent solution dispersity via stabilization with strong coordinating capping ligands. The ligand-assisted solid-state conversion strategy represents a general self-templating method for creating nanomaterials, as confirmed by its successful application to a wide range of morphologies (ellipsoids, rods, cubes, and plates) and compositions (hydroxides and metal–organic frameworks).