Layering transitions in colloidal crystals as observed by diffraction and direct-lattice imaging.
Layering transitions in colloidal crystals as observed by diffraction and direct-lattice imaging.
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通过衍射和直接晶格成像观察胶体晶体中的层状转变。
DOI：
10.1103/physreva.34.562
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
C. A. Murray
中科院分区：
文献类型：
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作者：
D. H. Winkle;C. A. Murray
本文用透射衍射和光学显微镜直接点阵成象方法研究了两个光滑玻璃表面间胶体晶体的分层转变。所研究的聚苯乙烯微球直径Φ= 0.305 μm，表面电荷为10104电子，在完全去离子水中，当体积浓度大于100.3%时，可形成三维胶体晶体。这些球在完全去离子水中的3D悬浮液形成体心立方（bcc）和面心立方（fcc）晶体结构，其作为胶体密度的函数，晶格常数在0.7和1.5 μm之间。当胶体被限制在距离D <$0.5 -1 μm的玻璃板之间时，球体形成单层二维流体。当D接近1 μm时，发生向单层二维六方晶体的转变。随着D的增加，从二维到三维晶体的演变被观察到作为一系列的结构转变区分板之间的晶面的数量和平行于玻璃边界的优选的晶体对称性。我们在这里提出了一个研究胶体晶体限制在一个楔形细胞，允许从同一微晶衍射和成像。我们目前的衍射和成像测量的结构相的一至七层胶体晶体之间的两个光滑的玻璃表面，为一系列的密度，使2< a s/Φ< 6。我们在干净样品的密度范围内观察到的结构相序列与Pieranski，Strzlecki和Pansu在s/Φ< 2时观察到的结构相序列相似但不相同，后者被建模为硬球系统。我们还观察到清洁的薄结晶相和添加了杂散电解质的“较脏”的薄相之间的差异。衍射和成像的使用被认为是必要的，以充分表征系统。
Layering transitions of colloidal crystals confined between two smooth glass surfaces have been studied by transmission diffraction of light as well as direct-lattice imaging with an optical microscope. The polystyrene spheres we studied have diameter Φ= 0.305 μm and a surface charge of∼ 10 4 electronic charges, and form three-dimensional (3D) colloidal crystals in completely deionized water at a volume concentration above≊ 0.3%. A 3D suspension of these spheres in completely deionized water forms both body-centered-cubic (bcc) and face-centered-cubic (fcc) crystalline structures as a function of colloid density n≡(1/a s) 3, with lattice constants ranging between 0.7 and 1.5 μm. When the colloid is confined between glass plates separated by distances D∼ 0.5–1 μm, the spheres form a single-layer 2D fluid. For D near 1 μm, a transition occurs to a single-layer 2D hexagonal crystal. As D increases, the evolution from two-to three-dimensional crystals is observed as a series of structural transitions distinguished by the number of crystal planes between the plates and by the preferred crystal symmetry parallel to the glass boundaries. We present here a study of colloidal crystals confined in a wedge cell that allows diffraction and imaging from the same crystallite. We present diffraction and imaging measurements of structural phases of one-through seven-layer colloidal crystals confined between two smooth glass surfaces, for a range of densities such that 2< a s/Φ< 6. The sequence of structural phases we observe for this range of densities for clean samples is similar but not identical to that observed for a s/Φ< 2 by Pieranski, Strzlecki, and Pansu, which was modeled as a hard-sphere system. We also observe differences between the clean thin crystalline phases and ‘‘dirtier’’thin phases to which a stray electrolyte has been added. The use of both diffraction and imaging was found necessary to fully characterize the system.