Baumgartner Jens, Ramamoorthy Raj Kumar, Freitas Alexy P, Neouze Marie-Alexandra, Bennet Mathieu, Faivre Damien, Carriere David
Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424 Potsdam, Germany.
Université Paris-Saclay, CNRS, CEA, NIMBE, LIONS, CEA Saclay, 91191 Cedex Gif sur Yvette, France.
Nano Lett. 2020 Jul 8;20(7):5001-5007. doi: 10.1021/acs.nanolett.0c01125. Epub 2020 Jun 24.
Crystallization from solution is commonly described by classical nucleation theory, although this ignores that crystals often form via disordered nanostructures. As an alternative, the classical theory remains widely used in a "multistep" variant, where the intermediate nanostructures merely introduce additional thermodynamic parameters. However, this variant still requires validation by experiments addressing indeed proper time and spatial scales (millisecond, nanometer). Here, we used in situ X-ray scattering to determine the mechanism of magnetite crystallization and, in particular, how nucleation propagates at the nanometer scale within amorphous precursors. We find that the self-confinement by an amorphous precursor slows down crystal growth by 2 orders of magnitude once the crystal size reaches the amorphous particle size (∼3 nm). Thus, not only the thermodynamic properties of transient amorphous nanostructures but also their spatial distribution determine crystal nucleation.
从溶液中结晶通常用经典成核理论来描述，尽管这忽略了晶体常常通过无序纳米结构形成这一事实。作为一种替代方法，经典理论仍在一种“多步”变体中被广泛使用，在这种变体中，中间纳米结构仅仅引入了额外的热力学参数。然而，这种变体仍需要通过涉及适当时间和空间尺度（毫秒、纳米）的实验来验证。在这里，我们使用原位X射线散射来确定磁铁矿结晶的机制，特别是成核如何在非晶态前驱体内部以纳米尺度进行传播。我们发现，一旦晶体尺寸达到非晶态颗粒尺寸（约3纳米），非晶态前驱体的自限作用会使晶体生长减慢2个数量级。因此，不仅瞬态非晶态纳米结构的热力学性质，而且它们的空间分布都决定了晶体成核。
