Methods template approach

The rational method features the functional approach and structural template approach. 

Early reports on electrospun scaffolds described poor cellular infiltration [175], Frequently, cells adhered at the surface and thus coated the nano- or submicrometer-scaled electrospun meshes due to the small pore size. In order to overcome this limitation, pore sizes were increased by combining ES with other methods. These approaches included the coating of microfibers with nanofibers [183], Other strategies combine ES with leaching [184, 185], freeze-drying [186], blowing agents [187], or ice templates [188],... 

A case in point is the template approach to preparing porons carbons [29], which affords a versatile and elegant method of controlling both the size and the spatial distribntion of nanometer-size pores. 

For the oxides that cannot he synthesized by the surfactant self-assembly, the hard-templating approach is a good choice. The key point for the nanocasting method is to increase the loading level of the precursors in the mesopore channels of the templates. Evidently, improving the interactions between template and precursor and between precursors themselves are essential in the hard-templating approach [11]. 

Other attempts follow the dual micellular templating approach involving a combination of block copolymers, surfactants, and alcohols [208]. The colloidal templating method produces three-dimensionally ordered macrostructures (3DOM-structures) [208]. However, even for the colloidal templating, the routes include besides the formation of the three-dimensionally arranged colloidal crystal always a second... 

A main chain polyrotaxane, a mechanically interlocked structure that can be considered as a string of pearls, in which the strand is the polymer backbone and the pearls are the cychc species threaded onto the strand. The backbone polymer can be a polyester, polyamide, poly(ethylene oxide), or virtually any linear polymer. The cyclic species are typically crown ethers, cyclodextrins (CDs), cucurbimrils, and calix-arenes. Polyrotaxanes can be made by two different methods statistical threading or via the template approach (enthalpi-cally driven). The statistical approach utilizes le Chatelier s principle with an excess macrocycle during the polymerization. The template approach is driven by attractive interactions of the macrocyclic species with either the monomer... 

In this chapter, we provide an overview of the recent research and development in the preparation, characterization, and application of novel porous carbons using both the endotemplate and the exotemplate methods. A discussion of zeolite templates for microporous carbons is followed by that of ordered mesoporous silica templates for OMCs, nanoparticle templates for mesoporous carbons, sol-gel processed porous carbons, self-assembled colloidal crystal templates for ordered macroporous carbons, and colloidal sphere templates for hollow carbon spheres, as well as other templating approaches to preparing carbon nanostructures. Then,... 

With regard to theoretical methods, several approaches based on statistical, hydro-phobic and pattern recognition methods have been proposed (Sawyer and Holt, 1993). Cumulative or joint prediction methods, with supplementary information from spectroscopic methods and the use of templates and sequence information from related proteins, were shown to improve the confidence of prediction, as assessed by comparison to X-ray crystallographic structures. Despite the great interest and advances in research in these areas, the accuracy of these secondary structure predictions (i.e. theoretical methods) still remains at only about 60%. Even when the structure of structurally related or homologous proteins is known, the accuracy of prediction is only 70.9% (Mehta et aL, 1995). Furthermore, these methods cannot easily be applied to monitor changes in protein secondary structure induced by processing. 

Compared with the various templating methods, some advantages associated with the colloidal silica templating method are the commercial availability of colloidal particles of various sizes, and of carbon precursors, such as mesophase pitches, organic monomers, polymers, and phenolic resins. Hence, the colloidal silica and opal templating approach are attractive for the possible large-scale production of nanoporous carbons. 

Sol-gel method (Zhang, 2002), replica process (Imai, 1999), and template approach (Kobayashi, 2000) have been reported as the procedures for the preparation of Ti02 nanotubes, and hollow tubes in the diameter of over 100 nm have been prepared. In practice, these materials have not been successfully commercialized as photocatalyst probably due to difficulties of its durability, costs, etc, however morphological approach may be effective in future application to air and water purification in light of its large surface area and unique structure like zeolite. 

The validation process caimot proceed until the protocol and all parties and their quality unit approves the acceptance criteria, which should be determined based on the required use and capabilities of the method. Although classical acceptance criteria, suitable for regulatory approval, are often available as a template approach, other statistical scientific approaches can also be justified." ... 

The hard-templating growth methods described before should not be confused, on the contrary, with soft-templating approaches which usually are accomplished in solution phase in the presence of free surfactant molecules which severely attend the nucleation of a new particle and the further shape development selectively and dynamically interacting with the evolving particle surface facets. 

Finally, as indicated in the Introduction, the template approach is a universal method for preparing nanomaterials. We and others have shown that this method can be used to make nanotubules and fibrils of polymers, metals, semiconductors, carbons, and other materials. This creates the interesting possibility of preparing nanowires and nanotubules that are composed (in a spatially controlled fashion) of more than one material. The simplest example is a nano-Schottky barrier composed of a nanowire segment of a semiconducting material in contact with a nanowire segment of an appropriate metal. We have recently described template-synthesized devices of this type [24]. 

---