Containers hard-template

A limitation of the hard template method is that the resulting materials must be stable in HF or NaOH solution and that the precursors must not react with the silica template at a high temperature. For example, in the formation of lithium containing transition metal oxides, it is necessary to first form the transition metal oxide as a mesoporous solid to prevent reaction of the alkali metal Li with the silica template and then to react the mesoporous transition metal solid with a lithium source, such as LiOH. 

As model systems, mixtures of PLA and organometallic complexes containing Pd and Pt dissolved in a common solvent were filled into the pores of hard templates [85,147]. After the evaporation of the solvent, tubes with a wall thickness of a few tens of nm were formed in which the metal precin-sors were dispersed. After thermolytic reduction, the evolution of nanoparticles consisting of the elemental metals inside the hquid polymeric matrix... 

The first reported procedures for the preparation of mesoporous sihca nanofibers by means of BCP soft templates inside hard templates were adaptations of synthetic strategies introduced by Stucky and coworkers [159]. Both tubular and soHd entities with a mesoporous fine structure can thus be prepared. In their pioneering work, Yang et aL filled sols containing Pluronic... 

Fig. 23 TEM image of released sUica nanowires containing a single row of mesocages obtained with PS(9500)-fc-PEO(9500) as the soft template and an AAO hard template (Dp = 35 nm). Reproduced from [185]. (2007) Wiley-VCH...

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. 

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