Colloidal Crystal Templates

Sadakane, M., Asanuma, T., Kubo, J. et al. (2005) Facile procedure to prepare three-dimensionally ordered macroporous (3DOM) perovskite-type mixed metal oxides by colloidal crystal templating method, Chem. Mater. 17, 3546. 

The method relies on the properties of monodispersed latex/silica spheres to assemble, through colloidal interactions, into a well-ordered, face-centered-cubic colloidal crystal upon centrifugation, sedimentation, electrophoresis, oscillatory shear or pressing in the form of pellets. Following pre-assembly of the colloidal crystal template, the precursor is infiltrated into the empty octahedral and tetrahedral interstitial sites that exist between the spheres. After conversion of the precursor to the desired material inside the voids, the template is removed leaving... 

In addition to recent advances in block co-polymer templating of periodic mesoporous silica and silica colloidal crystal templating of periodic mesopo-rous polymers [79], SAMs have been used for polymer patterning [80]. Mixtures of two strongly incompatible polymers, a polystyrene (PS)-polyvinylpyridine (PVP) blend, were found to phase separate when placed on a... 

Several approaches towards the synthesis of hierarchical meso- and macro-porous materials have been described. For instance, a mixture that comprised a block co-polymer and polymer latex spheres was utilized to obtain large pore silicas with a bimodal pore size distribution [84]. Rather than pre-organizing latex spheres into an ordered structure they were instead mixed with block-copolymer precursor sols and the resulting structures were disordered. A similar approach that utilized a latex colloidal crystal template was used to assemble a macroporous crystal with amesoporous silica framework [67]. 

Velev 0. D., Jede T. A., Lobo R. F., Lenhoff A.M., Microstructured porous silica obtained via colloidal crystal templates, Chem. Mater. 10 (1998) pp. 3579-3602. 

A general three-step procedure for the formation of macroporous materials by colloidal crystal templating is illustrated in Figure 6. In the first step, monodispersed colloidal spheres assemble into ordered 3D or sometimes 2D arrays to serve as templates. Secondly, the voids of colloidal crystals are filled by precursors that subsequently solidify to form composites. Finally, the original spheres are removed, creating a solid framework with interconnected voids, which faithfully replicate the template arrays. 

Figure 6 A schematic of the general procedure for preparing ordered macroporous materials by colloidal crystal templating. (1) Assembly of colloidal particles to form colloidal crystal template (2) Filling the interstices/voids with precursors to form composites and (3) Removal of templates. (Reprinted from Ref. 175, 2000, with permission from Elsevier)...

O.D. Velev, T.A. Jede, R.F. Lobo, and A.M. Lenhoff, Microstmctured Porous Silica Obained via Colloidal Crystal Template. Chem. Mater., 1998, 10, 3597-3602. 

Baia, M., Baia, L., and Astilean, S. (2005) Gold nanostructured films deposited on polystyrene colloidal crystal templates for surface-enhanced Raman spectroscopy. Chemical Physics Letters, 404, 3-8. 

Complex templates combine soft and hard template techniques. This methodology is used for synthesizing hierarchically bimodal and trimodal meso-macroporous materials with interconnected pore channels combining a surfactant template with a colloidal crystal template (Yuan and Su, 2004). 

Three-dimensionally ordered macroporous ceramic with high LR ion conductivity was prepared by colloidal crystal templating method using monodispersed polystyrene beads [12]. Monodispersed polystyrene beads with 3 pm diameter were dispersed in water and then filtrated by using a membrane filter under a small pressure difference. After this treatment, polystyrene beads were accumulated on the membrane filter with closed pack structure, as shown in Fig. 4.2. Then, the membrane consisting of accumulated polystyrene beads was removed from the membrane filter and put on a glass substrate. After drying at room temperature, the... 

Tessier, P.M. et al., Structured metalhc films for optical and spectroscopic applications via colloidal crystal templating, Adv. Mater, 13, 396, 2001. 

Further extension of the sol-gel and colloidal crystal templates include control of the outer shape of the colloidal crystal by assembling the PS particles in an aqueous droplet at the air/oil interface [23]. The assemblies then have regular shape (on the length scale of a few millimeters) spheres, ellipsoids, and concave disks. This was controlled by the addition of surfactant and an applied electric field. The cubic close-packed, ordered macroporous titania or silica obtained had similar outer shape as the template. 

Recently, inqjortant efforts have been made to fabricate photonic crystals by colloidal crystal templating [1-5], Colloidal crystals are self-organized arrays of silica or latex spheres, having the periodicity required for photonic band gaps. The basic idea is to use a colloidal crystal as a template, infiltrate the interstitial spaces between the spheres with another material and, then, remove the spheres by chemical etching or combustion. Since the resulting macroporous structures have a complete photonic bandgap [6,7], these materials have many applications in photonics. 

Fig.1 Scheme of preparation routes to macroporous networks by colloidal crystal templating... 

Codeposition, which represents the concurrent processes of colloidal crystal template formation and simultaneous filling of the interstitial sites with the desired framework material, is usually achieved by the deposition of a mixture of the templating colloids with the matrix material precursor (for example, a sol-gel precursor or nanoparticles). For this purpose, a dispersion of large particles, which will constitute the template, is mixed with nanoparticles of the framework material, which have to be small enough to easily fit into the interstitial space without interfering with crystal formation. By this method porous silica [25,32,35] and titania [32] were fabricated. 

Similarly to the codeposition procedure above, the metal can also be delivered as nanoparticles to the colloidal crystal template, but in this case after preparation of the template. This was demonstrated for gold nanoparticles, which were filled into the interstitial sites of a polymer opal by filtering a gold nanoparticle suspension through the preassembled opal with a filter small enough to hold back the nanoparticles [33]. The templating opal was prepared before in very much the same way by filtration of a PS latex suspension. 

Velev OD, Kaler EW (2000) Structured porous materials via colloidal crystal templat-ing from inorganic oxides to metals. Adv Mater 12 531... 

Stein A, Schroden RC (2001) Colloidal crystal templating of three-dimensionally ordered macroporous solids materials for photonics and beyond. Cnrr Opin Solid State Mater Sci 5 553... 

Miguez H, Meseguer F, Lopez C, Holgado M, Andreasen G, Mifsud A, Fornes V (2000) Germanium EGG structure from a colloidal crystal template. Langmuir 16 4405... 

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