Two-step crystal nucleation via capillary condensation
Two-step crystal nucleation via capillary condensation
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DOI：
10.1039/c3ce26887j
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发表时间：
2013-01-01
期刊：
影响因子：
3.1
通讯作者：
Christenson, Hugo K.
中科院分区：
文献类型：
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作者：
Christenson, Hugo K.
有许多例子表明经典成核理论不能正确描述溶液中晶体的形成。这些实例中的许多已被归类在术语“晶体成核的两步机制”下，因为共同点是最初形成更致密的、通常是亚稳的流体相，随后是从该前体成核晶体。许多成熟的结晶途径，如涉及生物矿物（如方解石和羟基磷灰石）的无定形前体相的结晶途径，都属于这一类，最近发现的许多蛋白质从稠密的流体分子簇中成核的情况也属于这一类。在这里，我们讨论了一个两步机制，已被实验确定在从蒸汽异相晶体成核。在这个过程中，过冷液体从表面空腔中的蒸汽冷凝，然后冻结，最有可能通过均匀成核。因此，在有利的条件下，晶体沉积可以从饱和蒸气中发生，而不需要任何过饱和。这些结果对大气冰成核具有重要的潜在意义，类似的想法在近50年前就提出了，但从未经过实验验证。与溶液结晶的热力学类比使我们建议，在溶液中的异质成核在许多情况下可能会进行类似的路线，已被发现在计算机模拟研究蛋白质成核在表面凹坑。
There are many examples where classical nucleation theory does not provide a correct description of the formation of a crystal from a solution. Many of these examples have been grouped together under the term "two-step mechanisms of crystal nucleation", because the common denominator is the initial formation of a denser, often metastable fluid phase, followed by nucleation of the crystal from this precursor. A number of well established routes to crystallisation, such as those involving amorphous precursor phases to biominerals like calcite and hydroxyapatite would fit into this category, as would the many recently discovered cases of protein nucleation from dense fluid clusters of molecules. We here discuss a two-step mechanism that has been experimentally identified in heterogeneous crystal nucleation from vapour. In this process, supercooled liquid condenses from vapour in surface cavities and then freezes, most likely via homogeneous nucleation. As a result, crystal deposition may under favourable conditions occur from saturated vapour with no need whatsoever for supersaturation. These results are of great potential significance for atmospheric ice nucleation, and similar ideas were advanced almost 50 years ago, but were never experimentally tested. Thermodynamic analogies with solution crystallisation lead us to suggest that heterogeneous nucleation in solution might in many cases proceed by a similar route, as has been found in computer simulation studies of protein nucleation in surface pits.