The preparation of mesoscopic rings in colloidal crystal templates.
The preparation of mesoscopic rings in colloidal crystal templates.
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DOI：
10.1002/anie.200460584
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发表时间：
2005-03
影响因子：
--
通讯作者：
F. Yan;W. Goedel
中科院分区：
文献类型：
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作者：
F. Yan;W. Goedel
2084 2005 Wiley-VCH Verlag GmbH & Co. KGaA，魏因海姆DOI：10.1002/anie. 200460584 Angew. Chem.Int.Ed.2005，44，2084-2088环腔[2]中的电场以及棒和开口环的阵列可以产生负折射率的材料。[3]这些影响是大小相关的。因此，需要优化环尺寸以适合预期的研究。特别是如果环状结构必须与可见光相互作用，则需要低至亚微米范围的尺寸。原则上，这种尺寸的环可以通过先进的光刻技术制造，但这些方法通常昂贵且分辨率或速度有限。作为替代，已经报道了从半导体、金属、聚合物和其他材料制备介观环的各种非光刻方法。[4-11]这些制备方法中的大多数是基于材料在二维结构化基底上的选择性沉积。例如，金环已经通过纳米结构模板（例如球形颗粒的二维阵列[2]或穿孔玻璃的薄片[8]），金属沉积和随后通过离子束蚀刻去除不需要的金属的适当组合来制备。金属，陶瓷和有机环已经通过选择性润湿胶体单层，[6]多孔膜，[7]或水滴[9]在平面基底上制备。由于毛细管力，液体前体以环的形式围绕这些物体聚集。然后将这些环固化并移除模板。然而，并不总是能够将环与下面的基板分离。此外，用于制备大量环的这些二维技术的升级本质上需要制备相对大的承载模板的基底。例如，通过选择性润湿平面基底和直径为1 μm的单层球体之间的接触点来制备环，每平方米约产生1012个环。如果环在密堆积结构（fcc或hcp）中相同球体的相互接触点处组装，即使1 mL这种三维模板也足以产生八倍数量的环。[12]因此，期望将通过毛细力组装的概念扩展到第三维。在这里，我们报告说，通过毛细管力的环制备的概念确实可以扩展到简单的三维结构。该制备基于用液体部分填充胶体晶体，在颗粒之间的接触点周围的楔形中组装液体，固化所得液体环，以及随后去除模板颗粒（图1）。这种方法与以前的工作有关，其中胶体晶体的完全填充或内部界面的完全覆盖被用于一般的三维多孔材料。[13-19]然而，由于液体被限制在颗粒之间的楔形物中，我们得到了孤立的环，而不是三维宏观体。根据Stöber的方法[20]合成了均匀尺寸的二氧化硅球，并通过用3-（三甲氧基甲硅烷基）丙基甲基丙烯酸酯（TPM）涂覆它们来疏水化。[21]最初悬浮在乙醇中的颗粒通过离心被包装成三维胶体晶体。在室温下通过蒸发除去乙醇后，用非挥发性化合物的溶液填充晶体。
2084 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/anie. 200460584 Angew. Chem. Int. Ed. 2005, 44, 2084–2088 electrical fields in the ring cavity,[2] and arrays of rods and split rings can give rise to materials of negative refractive index.[3] These effects are size dependent. It is therefore desirable to optimize the ring size to suit the intended investigation. Especially if the ringlike structures have to interact with visible light, dimensions down to the submicrometer range are necessary. In principle, rings of that size can be made by advanced lithographic techniques, but these methods are often expensive and limited in resolution or speed. As an alternative, various nonlithographic methods to prepare mesoscopic rings from semiconductors, metals, polymers, and other materials have been reported.[4–11] Most of these preparation methods are based on the selective deposition of materials on two-dimensionally structured substrates. For example, gold rings have been prepared by a suitable combination of nanostructured templates (such as twodimensional arrays of spherical particles [2] or thin slices of perforated glass [8]), metal deposition, and subsequent removal of unwanted metal by ion-beam etching. Metal, ceramic, and organic rings have been prepared by selective wetting of colloidal monolayers,[6] porous membranes,[7] or water droplets [9] on planar substrates. Due to capillary forces, liquid precursors assembled around these objects in the form of rings. These rings were then solidified and the templates removed. However, it is not always possible to separate the rings from the underlying substrates. In addition, upscaling of these two-dimensional techniques for the preparation of rings in larger quantities inherently requires the preparation of comparatively large substrates bearing the templates. For example, the preparation of rings by selective wetting of the contact points between a planar substrate and a monolayer of spheres 1 μm in diameter yields approximately 1012 rings per square meter. If the rings were assembled instead at the mutual contact points of the same spheres in a close-packed structure (fcc or hcp), even 1 mL of this three-dimensional template would suffice to generate the eightfold number of rings.[12] It is thus desirable to extend the concept of assembly by capillary forces into the third dimension. Here, we report that the concept of ring preparation by means of capillary forces can indeed be extended to simple three-dimensional structures. The preparation is based on the partial filling of colloidal crystals with a liquid, the assembly of the liquid in the wedges around the contact points between the particles, the solidification of the resulting liquid rings, and the subsequent removal of the templating particles (Figure1). This approach is related to previous work in which complete filling of colloidal crystals or complete coverage of the internal interfaces was used to general three-dimensional porous material.[13–19] However, due to the confinement of the liquid in the wedges between particles we obtain isolated rings instead of a three-dimensional macroscopic body.Silica spheres of uniform size were synthesized according to Stöber s method [20] and hydrophobized by coating them with 3-(trimethoxysilyl) propyl methacrylate (TPM).[21] The particles initially suspended in ethanol were packed into a three-dimensional colloidal crystal by centrifugation. After the ethanol was removed by evaporation at room temperature, the crystals were filled with a solution of a nonvolatile