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).

中文翻译：

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配体辅助的纳米粒子固态转化

热处理通常是改善纳米材料性能的理想方法，然而，这通常会导致不良问题，例如聚集和形状变形。在这里，我们通过开发用于形状保留的纳米结构化学转化的配体辅助煅烧策略来克服这一挑战。虽然通常认为封盖配体在溶液相合成中是有效的，但我们证明了它们在高温煅烧过程中的存在不仅保持了整体颗粒形态，而且还提供了在金属氧化物纳米结构中有效产生可控孔隙率的可能性。我们证明这种策略，它涉及β-的FeOOH椭圆体成多孔的化学转化的特别优雅的例子的α-Fe ₂ ö ₃磁性Fe ₃ O ₄椭球体，具有形态学上的保存性，并通过强大的配位帽配体稳定而具有出色的溶液分散性。配体辅助的固态转化策略代表了一种创建纳米材料的通用自模板方法，这一点已被成功应用于多种形态（椭圆形，棒状，立方体和板状）和成分（氢氧化物和金属有机化合物）所证实。构架）。