Hard templates synthesis

The chemical methods for the preparation of nanomaterial could be categorized as either template-directed or template-free. The template synthesis methods commonly used for the production of one-dimensional nanostructured PANI are further subdivided into hard template (physical template) synthesis and soft template (chemical template) synthesis approach according to the solubility of the templates in the reaction media. Non-template routes for the synthesis of one-dimensional nanostructured PANI such as rapid-mixing reaction method, radiolytic synthesis, interfacial polymerization, and sonochemical synthesis have also been reported [56], Other approaches like combined soft and hard template synthesis are also known. An overview of hard-template, soft-template, and template-free procedures are presented in the following paragraphs. 

The disadvantage of traditional hard template synthesis of porous carbon is that it usually involves several steps starting with the preparation of a mesoporous silica/surfactant mesophase followed by calcination to remove the surfactant (to generate the mesoporous sUica hard template), introduction of carbon precursor into the mesoporous siUca, carbonisation of the carbon precursor and finally silica etching (i.e. washing with HF or NaOH) to generate the mesoporous carbon. Therefore, recently there have been some attempts to prepare mesoporous carbon via more direct methods involving fewer steps. 

In hard-template synthesis, since mesoporous carbons are obtained as inverse replicas of the silica templates, the carbons generally retain the particle morphology of the templates. Accord-... 

K. Jackowska, A. T. Biegunski, and M. Tagowska, Hard template synthesis of conducting polymers a route to achieve nanostructures, J. Solid State Electrochem., 12, 437-443 (2008). 

Hard-tcmplatc synthesis can provide micro- and nanocontainers with a controlled geometric shape. However, this approach requires complicated synthetic steps, including the dissolution of the template in corrosive media. Collapse of the hollow structure after template removal is also a critical problem. Therefore, the potential drawback of using hard templates forced scientists to search for more efficient and facile routes to prepare CPCs. Among these newly developed approaches, the soft-template method is considered a powerful tool as an alternative strategy to hard-template synthesis. 

Recently, a facile soft template synthesis was developed for fabricating PPy nanotubes against the hard template synthesis [153,249]. PPy nanotubes could be readily produced through a cylindrical micelle templating in re-... 

FIGURE 6 Schematic of the hard-template synthesis of different conducting polymer nanostructures. 

Hollow noble metal nanostructures are proposed as containers for drug delivery as well as low density inert packing materials for composite materials. In addition, they have unique plasmonic and catalysis properties. Many methods have been used to produce these materials including hard template synthesis of nanotubes mentioned earlier in this chapter. 

Fig. 9 Hard template synthesis for nanotubes and nanowires using porous membrane...

F%. 10 Hard template synthesis for nanotubes using nanofibtas as template... 

Keywords hard template synthesis, CuO-Ce02 nanostractured catalysts, WGS reaction... 

Although hard-templating synthesis provides a simple and versatile pathway to fabricate ID perovskite nanomaterials, the quantity produced in each run is relatively small. Removal of the template through a post-synthesis process may also cause damage to the product. Furthermore, the so-obtained samples are often polycrystalline, which may limit their use in device fabrication and fundamental studies [42]. Therefore, it is highly demanded to develop alterative methods that are effective to synthesize ID perovskite nanomaterials. 

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