Templated inorganic materials

One limitation of traditional sol-gel MIMs is the limited possibility to introduce 

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Nanostructured polymers, in particular block copolymers, have immense potential in areas ranging from templating inorganic materials to permeation/ filtration media, nano-assaying, nanolithography and high density data storage media. 

Although the majority of the examples in the literature have used viral capsids to nudeate and template inorganic materials, it is also possible to template the formation of organic polymers on their surface. Niu et used the TMV capsid as a scaffold to bind and polymerize pyrrole and aniline into conductive polymer nanowires. Using the capsid as the scaffold allowed for the creation of well-defined constmcts with a low polydispersity, high processability, and a high aspect ratio. 

Pulsed laser deposition involves striking a target made of pre-prepared surfactant-templated inorganic material with an intense laser beam, causing the ejection of atoms, ions and fragments containing template that deposit onto a substrate. Continuous well-adhered films of nanometer scale particles of mesophase material tens of nanometers to... 

Ni [182], V [183], and A1 [184]. SU-M [185] is a mesoporous germanium oxide with crystalline pore walls, possessing one of the largest primitive cells and the lowest framework density of any inorganic material. The channels are defined by 30-rings. Structural and thermal information show that there exists a mismatch between framework stability and template decomposition. The latter requires temperatures higher than 450 °C, while the structure is preserved only until 300 °C. 

Woolfson and Mahmoud have classified the routes to preparation of decorated self-assembling peptide materials [53] as (1) co-assembly, where the functional part is already attached to a self-assembling component prior to assembly, and (2) postassembly, where a non-functionahsed self-assembled structure is modified by covalent or non-covalent means. This discussion adheres to this classification. A third route, beyond the scope of this review, is the use of structured peptides as templates for inorganic materials. Section 4.1 discusses functionalised self-assemblies formed from co-assembly-type approaches, while post-assembly modifications of self-assembled structures are considered in Sect. 4.2. 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

By using other templates, the size of metal nanoparticles can be also controlled. Chen et al. reported the sonochemical reduction of Au(III), Ag(I) and Pd(II) and synthesis of Au, Ag and Pd nanoparticles loaded within mesoporous silica [48,49]. Zhu et al. also reported the sonochemical reduction of Mn04 to Mn02 and synthesis of Mn02 nanoparticles inside the pore channels of ordered mesoporous cabon [50]. Taking into account these reports, the rigid pore of inorganic materials can be used as a template for the size controlled metal nanoparticle synthesis even in the presence of ultrasound. 

Compared to inorganic materials, organic materials such as polymers, surfactant molecules and micelles also act as a capping material or soft template. Figure 5.15 shows TEM images of gold nanorods and nanoparticles synthesized by sonochemical reduction of Au(I) in the presence of cetyltrimethylammonium bromide,... 

Numata, M., Sugiyasu, K., Hasegawa, T. and Shinkai, S. (2004) Sol-gel reaction using DNA as a template An attempt toward transcription of DNA into inorganic materials, S. Angewandte Chemie-International Edition, 43, 3279-3283. 

Most examples discussed so far made use of amorphous inorganic supports or sol-gel processed hybrid polymers. Highly disperse materials have recently become accessible via standard processes and, as a result, materials with various controlled particle size, pore diameter are now available. Micelle-templated synthesis of inorganic materials leads to mesoporous materials such as MCM-41, MCM-48, MSU, and these have been extensively used as solid supports for catalysis [52]. Modifications of the polarity of the material can increase the reactivity of the embedded centre, or can decrease its susceptibility to deactivation. In rare cases, enhanced stereo- or even... 

Smarsly, B. Antonietti, M. 2006. Block copolymer assemblies as templates for the generation of mesoporous inorganic materials and crystalline films. Eur. J. Inorg. Chem. 1111-1119. 

Fig. 9 Schematic representation of three approaches to generate nanoporous and meso-porous materials with block copolymers, a Block copolymer micelle templating for mesoporous inorganic materials. Block copolymer micelles form a hexagonal array. Silicate species then occupy the spaces between the cylinders. The final removal of micelle template leaves hollow cylinders, b Block copolymer matrix for nanoporous materials. Block copolymers form hexagonal cylinder phase in bulk or thin film state. Subsequent crosslinking fixes the matrix hollow channels are generated by removing the minor phase, c Rod-coil block copolymer for microporous materials. Solution-cast micellar films consisted of multilayers of hexagonally ordered arrays of spherical holes. (Adapted from [33])...

In either the transcriptive or synergistic strategy, removal of the organic template by extraction or calcination renders the inorganic mesoporous structure. For synthetic schemes that are not compatible with the formation of stable template assemblies, an alternative approach is to use a preformed, templated inorganic host, such as mesoporous silica, as a mold to nanocast the desired material as an inverse replica of the host, such as that seen in Figure 14. ... 

One strategy is to fabricate a template structure using polymeric material (thus, using the same chemistry as described in Sects. 5.2 and 5.3) and back-fill or coat this structure with inorganic materials. For example, surface modification, followed by electroless deposition of Ag [217-219] or Cu [220], or by chemical reduction of Au solutions by surface functionalities [220], has been used to obtain metallized structures, while infiltration of polymeric photonic bandgap-type structures with Ti(0 Pr)4 solution, followed by hydrolysis and calcination, has been used to obtain highly refractive inverted Xi02 structures [221]. Au has also been deposited onto multiphoton-patterned matrices of biomaterials [194]. 

Fig. 77. Schematic drawing of the liquid-crystal templating mechanism. Hexagonal arrays of cylindrical micelles form (possibly mediated by the presence of silicate ions), with the polar groups of the surfactants (light grey) to the outside. Silicate species (dark grey) then occupy the spaces between the cylinders. The final calcination step burns off the original organic material, leaving hollow cylinders of inorganic material [473]...

The high acidity of the unique sulfonic acid function of Nafion can also be utilized by tethering perfluoroalkanesulfonic acid groups to the surface of various silicas. Two approaches have been described to prepare such hybrid organic-inorganic materials. The grafted materials 3 have been prepared by reacting preformed silica materials (MCM-41, SBA-15) with sultone 2 [Eq. (2.31)].165 Co-condensation of tetraethoxy-silane with 4 in the presence of dodecylamine template, in turn, furnished the HMS-based material 5 [Eq. (2.32)].166,167... 

The kinds of structures adopted by these microorganisms as well as other mineral morphologies, are the subject of increasing study as chemists look at soft templated routes to nanoscale objects. Early work in the 1990s by a team at Mobile used supramolecular micelles, lamellae and bicontinuous phases4 formed by amphiphiles, to assemble inorganic materials, particularly silica and alumina. A range of new... 

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