Single crystals with complex form via amorphous precursors
Single crystals with complex form via amorphous precursors
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DOI：
10.1002/anie.200800418
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Coelfen, Helmut
中科院分区：
文献类型：
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作者：
Coelfen, Helmut
固体的受控形态发生在科学技术中非常重要，因为固体的许多性质取决于其大小、形状和组织。因此，投入了大量的研究工作来控制降水事件。产生具有可控形状的固体的一种策略是应用模板，其充当随后沉淀反应的模具。这种方法适用于无定形的，因此各向同性的材料，它可以适应任何形状，复制甚至结构下降到只有几个纳米的范围。例如，在所谓的纳米铸造方法中利用这种性质，这对于多孔材料的产生特别有吸引力。[1，2]然而，晶体材料更难以模板化，因为它们本质上是各向异性的，具有由其晶胞决定的矢量不同的原子排列，其在均质体的晶格中周期性地复制。单晶体显示出具有限定角度的轮廓分明的面，这是对晶体物质的一般理解。晶体构建单元的预定义各向异性可能与具有复杂形状的外部模板的空间约束相冲突。生物矿物，另一方面，往往表现出非常复杂的形态与曲率，没有任何明显的晶面。一个例子是海胆的骨骼元素。虽然它们被认为是方解石的单晶，但它们具有非常复杂的形状（图1，左）。这种复杂性与方解石通常采用的菱面体形式形成鲜明对比（图1，右）。
Controlled morphogenesis of solids is of great importance in science and technology, as many properties of solid bodies depend on their size, shape, and organization. Consequently, much research effort is invested to obtain control over precipitation events. One strategy to generate solids with controllable shape is the application of templates, which act as a mold for the subsequent precipitation reaction. This approach works well for amorphous and thus isotropic materials, which can adapt to any shape, replicating even structures down to the range of only a few nanometers. This property is exploited, for example, in the so-called nanocasting approach, which is especially attractive for the generation of porous materials.[1, 2] Crystalline materials, however, are much more difficult to template since they are anisotropic in nature with vectorially different atomic arrangements dictated by their unit cell, which are periodically replicated in the crystal lattice of the homogeneous body. Single crystals exhibit well-defined faces with defined angles, which is the general understanding of a crystalline substance. The predefined anisotropy of the crystal-building units potentially conflicts with the spatial constraints of an external template with complex shape. Biominerals, on the other hand, often show very complex morphologies with curvature and without any obvious crystal faces. One example is the skeletal elements of sea urchins. Although they are considered to be single crystals of calcite, the thermodynamically stable CaCO3 polymorph, they have a very complex shape (Figure 1, left). This complexity is in large contrast to the rhombohedral form which is normally adopted by calcite (Figure 1, right).