Colloidal ordered arrays

Fabrication of composite colloidal spheres involves two steps submicron particles are fabricated from a material preferentially responsive to one class of chemicals followed by a step in which the submicron spheres are coated with a shell that is preferentially responsive to another class of chemicals. A colloidal crystal array is subsequently self-assembled into a 3D ordered film. 

Colloidal zeolites have been used as building blocks to fabricate hierarchical porous materials. Infiltrating ethanol sol of zeolite nanoparticles into an ordered array of polystyrene spheres resulted in macroporous zeolites, which involves a self-assembly process. After ethanol evaporation, zeolite nanoparticles were aggregated by capillary forces. High concentration of external silanol groups favored the formation of hydrogen bonds between particles and eventually Si-O-Si bonds after calcination. The method has been further developed to produce transparent and self-standing zeolite membranes with controlled mesoporosity. Concurrently, the preformed zeolite-coated polystyrene spheres have been... 

The use of colloidal metallic nanoclusters deposited onto solid substrates can provide a higher degree of control over the SPs spectral properties state-of-the-art results in the chemical synthesis showed, in fact, the possibility to grow nano-objects with high uniformity and low size dispersion [36-38], This can allow to fabricate extended substrates, in which the local morphology, and thus the resulting MEF effect, can be controlled with good precision [19, 39], As a counterpart, still some randomness is unavoidable in this approach, since it is not simple to define the position of the nanoclusters on the substrate with micrometer precision to realize, for instance, ordered arrays of metallic particles. 

Macroporous VPO Phases. - The macroscale templating of bulk mixed metal oxide phases in the presence of colloidal sphere arrays typically consists of three steps shown in Figure 18. First, the interstitial voids of the monodisperse sphere arrays are filled with metal oxide precursors. In the second step, the precursors condense and form a solid framework around the spheres. Finally, the spheres are removed by either calcination or solvent extraction leading to the formation of 3D ordered macroporous structures [137]. 

Ordered macroporous materials (OMMs) are a new family of porous materials that can be synthesized by using colloidal microspheies as the template. - The most unique characteristics of OMMs are their uniformly sized macropores arranged at micrometer length scale in three dimensions. Colloidal microspheres (latex polymer or silica) can self assemble into ordered arrays (synthetic opals) with a three-dimensional crystalline structure. The interstices in the colloidal crystals are infiltrated with a precursor material such as metal alkoxide. Upon removal of the template, a skeleton of the infiltrated material with a three-dimensionally ordered macroporous structure (inverse opals) is obtained. Because of the 30 periodicity of the materials, these structures have been extensively studied for photonic applications. In this paper, the synthesis and characterization of highly ordered macroporous materials with various compositions and functionalities (silica, organosilica, titana, titanosilicate, alumina) are presented. The application potential of OMMS in adsorption/separation is analyzed and discussed. 

Scientists have spent a great deal of effort in recent years learning to synthetically emulate nature s ability to assemble particles into ordered arrays so as to more efficiently control the characteristics of light via reflection or transmission. From these efforts, signihcant scholarship has been realized on forming such colloidal crystals. 

Murray, C.A. and Grier, D.G., Colloidal crystals — solid particles suspended in fluid form ordered arrays with unusual and useful physical properties. Am. Set, 83, 238, 1995. 

Burkert K, Neumann T, Wang JJ, Jonas U, Knoll W, Ottleben H (2007) Automated preparation method for colloidal crystal arrays of monodisperse and binary colloid mixtures by contact printing with a pintool plotter. Langmuir 23 3478 Park J, Moon J, Shin H, Wang D, Park M (2006) Direct-write fabrication of colloidal photonic crystal microarrays by ink-jet printing. J Colloid Interface Sci 298 713 Gu ZZ, Kubo S, Fujishima A, Sato O (2002) Infiltration of colloidal crystal with nanoparticles using capillary forces a simple technique for the fabrication of films with an ordered porous structime. Appl Phys A 74 127... 

Colloidal Crystalline Arrays Colloidal spheres of silica and of polymers can be made relatively monodisperse, with standard deviations of 4% of the mean diameter for silica and 1% for polymer latexes. The spheres pack as shown in Figure 11.22a from fluid dispersions into fee (sometimes hep or bcc) colloidal crystals (CC) by gravity, by membrane filtration, or by capillary forces at the surface of an evaporating dispersion (80-82). The crystalline order of the materials is strictly at the length scale of the packed colloidal particles the packing of the atoms and molecules within the silica and polymer particles is totally amorphous. The CCs diffract... 

The preparation of ordered arrays of colloidal particles in three dimensions has been studied in the past primarily as a model for phase transition processes [15]. Colloid... 

Kim et al fabrieated SWNT composite films with ordered voids by using saerificial 2D siliea colloidal template (Figure 6.7). Experimentally, SWNTs stabilized with water-soluble polythiophene were mixed with a suspension of silica colloidal particles, and then assembled into 2D colloid-SWNT array on flexible substrate. Selective removal of silica colloids led to a composite film... 

The CCA, however, can be prepared as macroscopically ordered arrays of non-close-packed spheres. This self assembly is the result of electrostatic repulsions between colloidal particles, each of which has numerous charged surface functional groups. We have concentrated on the development of CCA which diffract light in the visible spectral region, and have generally utilized colloidal particles of ca. 100 nm diameter (7). These particles have thousands of charges which result from... 

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