Tetrahedral calcite crystals facilitate self-assembly at the air-water interface.
Tetrahedral calcite crystals facilitate self-assembly at the air-water interface.
复制标题
四面体方解石晶体有利于在空气-水界面处的自组装。
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
D. Weitz
中科院分区：
文献类型：
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作者：
S. Hashmi;H. Wickman;D. Weitz
方解石晶体通常在碳酸钙溶液中成核和生长，这些微晶可能被困在空气-水界面，在那里它们形成不寻常的结构。最常见的是分形结构，它可以在界面的很大一部分上延伸，其起源是根据颗粒的聚集来理解的。更罕见的是，观察到一种不同的和完全出乎意料的结构：颗粒在界面上保持良好的分离，形成一个有序的相，让人想起二维胶体晶体。形成这种有序相的微晶的结构总是观察到四面体，与形成分形相的微晶的更常见的菱形结构相反。我们表明，导致这种有序相的粒子间相互作用势是长程吸引力和长程排斥力之间的平衡。吸引力来自重力诱导的毛细力，而排斥力来自由于四面体晶体的带电表面而引起的偶极-偶极相互作用。的相互作用势估计从粒子的热运动，并拟合到理论上预期的值表明，四面体晶体上的有效表面电荷是西格玛约0.01电荷/nm 2。
Calcite crystals often nucleate and grow in solutions of calcium carbonate, and these crystallites can become trapped at the air water interface, where they form unusual structures. The most common is a fractal structure, which can extend over a large fraction of the interface, and whose origin is understood in terms of the aggregation of the particles. Much more rarely, a different and entirely unexpected structure is observed: the particles remain well separated on the interface, forming an ordered phase reminiscent of a two-dimensional colloidal crystal. The structure of the crystallites that form this ordered phase is always observed to be tetrahedral, in contrast to the much more common rhombohedral structure of the crystallites that form the fractal phase. We show that the interparticle interaction potential that leads to this ordered phase is a balance between a long-range attractive interaction and a long-range repulsive interaction. The attraction results from gravity-induced capillary forces, while the repulsion results from a dipole-dipole interaction due to the charged surface of the tetrahedral crystals. The interaction potential is estimated from the thermal motion of the particles, and fits to the theoretically expected values suggest that the effective surface charge on the tetrahedral crystals is sigma approximately 0.01 charges/nm2.