Template techniques

The second class of materials, which we will consider herein are carbons with a highly ordered porosity prepared by a template technique [15-18]. The pores are characterized by a well-defined size determined by the wall thickness of the silica substrate used as substrate for carbon infiltration. They can be also interconnected, that is very useful for the charge diffusion in the electrodes. Figure 1 presents the general principle of the carbon preparation by a template technique, where the silica matrix can be, for example, MCM-48 or SBA-15. 

Figure 1. Schematic representation of carbon elaboration by a template technique.

Colloidal templating techniques offer the potential of precise mning for drug-release applications (see Section 8.2.4). For instance, the Feldheim group used gold... 

By the template technique using anodic oxide films and pyrolytic carbon deposition, one can prepare monodisperse carbon tubes. Since the length and the inner diameter of the channels in an anodic oxide film can easily be controlled by changing the anodic oxidation period and the current density during the oxidation, respectively, it is possible to control the length and the diameter of the carbon tubes. Furthermore, by changing the carbon deposition period, the wall thickness of the carbon tubes is controllable. This template method makes it possible to produce only carbon tubes that are not capped at both ends. Various features of the template method are summarized in Table 10.1.1 in comparison with the conventional arc-discharge method. 

By applying the template technique, Kyotani et al. and Che et al. succeeded in preparing Pt and Pt/Ru metal-filled uniform carbon nanotubes in which the metal is present as either nanorods or nanoparticles. It should be noted that no metal was observed on the outside wall of the tubes. This is due to the preparation procedure, in which the metal precursor was loaded into the carbon-deposited alumina film before the dissolution of alumina by HF (see Fig. 10.1.9). Thus, there is no other space for metal to be loaded except in the channels. 

As demonstrated in this chapter, the template technique using anodic oxide films makes it possible to control the length, diameter, and thickness of carbon lubes and... 

Replacement of the hydrogen bonds in oxime complexes with boron bridges leads to macrocyclic complexes such as those from dimethyl glyoxime (equation 59).201,202 This kinetic template technique has been used for the encapsulation of metals inside cage ligands.203 204... 

The functionalisation also allows extending the complexity of intertwined molecular assemblies involving molecular catenanes, rotaxanes and knots. Elaborate interlocked assemblies constructed by means of metal-templation techniques and ji-ji-stacking preorganisation were reviewed [3, 11], Our last survey was devoted to the hydrogen bond templated synthesis of amide-based catenanes and rotaxanes [32], Since then a considerable advancement in elucidation of mechanisms of templation and derivatisation of the amide-based interlocked structures has been reached. Moreover, in 2000 we reported a one pot synthesis of amide-based knots such as 8 [21], which is so far the easiest preparation of molecular knots. In the following, specific possibilities of functionalisation of amide-based catenanes, rotaxanes and knots will be discussed. 

The procedure of the anion-templated synthesis was later used for the preparation of various rotaxanes by the groups of Smith [41] and Schalley [34-36], The anion-templation technique was carefully tested by Schalley et al. Altering the length of the axle-center pieces and the size of stopper groups they synthesized a variety of rotaxanes and analysed their yields and de-slipping rates [34, 35],... 

Chemical modification of CNTs changes or improves their chemical and electrical properties, thereby expanding their application fields. All of the efforts for the chemical modification have been directed toward the outer surface of CNTs. No one has, however, attempted to differentiate between the outer and inner surfaces or to modify only the inner one while leaving the outer one as it is. One of the reasons for this is that both ends are generally closed for most CNTs, but even if they were open, such differentiation would be essentially impossible any chemical treatment to the inner surface always affects the outer one. Only the template technique enables such selective chemical modification of the inner surface of nanotubes. With this technique, CNTs with outer and inner surfaces that have different properties can be prepared, and unique adsorption behaviors and electrical properties can be expected from such CNTs with heteroproperties. 

This kind of carbon with such unique pore structure, extremely large surface area, and micropore volume has never been reported. Sections 3.3.3.1 and 3.3.3.2 will introduce the details of the production method of the ordered microporous carbons and compare the extraordinary pore structure of this carbon with commercial microporous carbons with a large surface area. In Section 3.3.3.3, it will be demonstrated that a similar ordered microporous carbon containing N atoms can be prepared by the template technique, and the N-doping influences the adsorption behavior of H20 molecules [136], In Section 3.3.3.4, the use of this unique carbon as an electrode for supercapacitor will be introduced [137],... 

More effective nanoporous carbons have been obtained by the template technique. A nitrogenated precursor is introduced in a nanoporous scaffold and subsequently pyrolyzed then the nitrogen-enriched replica is obtained by etching the host with hydrofluoric acid. The first materials of this... 

There are numerous approaches to the synthesis of highly dispersed metal oxides in addition to those discussed. These include some methods that have been less commonly used to prepare metal oxides, such as vapor condensation methods, spray pyrolysis and templated techniques. 

In recent years, varieties of porous materials have been obtained by templated techniques. Generally two types of templates have been reported in the literature. 

Sol-gel processes are also suitable for lanthanide oxide formation, as could be shown by the use of Tb(acac)3 and Dy(OBu- )3 in acetylacetone" . Tb203 crack- and pine-hole-free, dense and smooth microstructured buffer layers were produced on nickel tapes by a reel-to-reel continuous sol-gel process. The authors report that the film properties can be strongly influenced by solution components, temperature, time and atmosphere. Nanocrystalline mesoporous dysprosium oxide Dy203 with narrow monomodal pore size distribution can be approached by a combined sol-gel process with a surfactant-assisted templating technique . The spherical Dy203 nanoparticles were formed with aggregations. 

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