Templated crystallization

Seeds of isostructural or quasi-isostructural species that crystalUze well can also been employed to induce crystalUzation of unyielding materials [61]. Heteromolecular seeding [62], whereby near isostructural compounds can be used to template crystallization in less accessible or elusive desired crystal forms, can be apphed. For instance, chiral co-crystals of tryptamine and hy-drocinnamic acid were prepared by crystalUzation in the presence of seeds of different chiral crystals [63]. Of course, imintentional seeding may also alter the crystalUzation process in an undesired manner [64]. 

Steed, J. W., Goeta, A. E., Lipkowski, J., Swierczynski, D., Panteleon, V., Handa, S., Templated crystal nucleation mixed crystals of very different copper(U) N,N,N -trimethyltriazacyclononane complexes. Chem. Commun. 2007, 813-815. 

Addadi, L., Joester, D., Nudelman, F., and Weiner, S. "Mollusk shell formation A source of new concepts for understanding biomineralization processes". Chem. Eur.. 12(4), 981-987 (2006). Ajikumar, P.K., Lakshminarayanan, R., and Valiyaveettil, S. "Controlled deposition of thin films of calcium carbonate on natural and synthetic templates". Crystal Growth Des. 4(2), 331-335 (2004). 

Davidson (2002) Mesoporous silica Structure evolution, role of templates crystallization variables + + n.a. Synthesis of mesoporous silica with defined properties... 

The Si02 walls are built up by condensation processes, for which the anchored silicate species act as nucleation points. The enrichment of the oxide at the templating crystals occurs by an Ostwald ripening mechanism the particles grow in size at the tube walls and highly soluble very small silica particles re-dissolve to the reaction solution. The polycondensation reaction is finished within about I2h. 

Sample Proportion Na Al P Sn Si T Template Crystallization temp. Structure Adsorption... 

The materials which have been mentioned here so far are predominantly shaped in planar films of hierarchical order. However, the synthesis of hierarchically structured particles is also highly desirable, as they might be further processed and used for the preparation of composite porous materials. Wu et al. showed the synthesis of raspberry-like hollow silica spheres with a hierarchically structured, porous shell, using individual PS particles as sacrificial template [134]. In another intriguing approach by Li et al. [135], mesoporous cubes and near-spherical particles (Fig. 10) were formed by controlled disassembly of a hierarchically structured colloidal crystal, which itself was fabricated via PMMA latex and nonionic surfactant templating. The two different particle types concurrently generated by this method derive from the shape of the octahedral and tetrahedral voids, which are present in the template crystal with fee lattice symmetry. 

The above discussions have highlighted the utility of both magnetic arrays and colloidal-templated crystals for DNA electrophoresis. While the variety of solid supports that can be fabricated by these techniques is limited when compared to those available through micro- and nanofabrication, the ease with which these self-assembled arrays can be constmcted confers significant advantages... 

Srivatsan, S.G. Parvez, M. Verma, S. Modeling of prebiotic catalysis with adenylated polymeric templates Crystal structure studies and kinetic characterization of template-... 

Crystals of calcium salts have also been used for imprinting polymers of carboxyhc acid functional monomers. Instances include imprinting artificial polymers with calcite to act as a template for the growth of specific crystal phases [95]. It has been reported that the calcite-imprinted polymers induced the formation of calcite nuclei even when the reaction conditions favored the growth of its other polymorph, namely aragonite. Another example of such work is the nucleation of calcium oxalate crystals on an imprinted polymer surface [96] where 6-methacrylamidohexanoic acid/divinylben-zene copolymers imprinted with calcium oxalate monohydrate (COM) or dihydrate (COD) crystals were used to foster the nucleation of CaOx crystals. The results revealed that the polymers gave rise to the formation of crystals that were the polymorphs of the template crystals. 

Garcia-Gutierrez, M.C., Hernandez, J.J., Nogales. A., Pantine, P., Rueda, D.R., and Ezquerra, T.A. (2008) Influence of shear on the templated crystallization of poly (butylene terephfhalate)/single wall carbon nanotube nanocomposites. Macromolecules, 41, 844-851. 

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