Replica formation, porous

The formation of open and porous structures with extremely large surface area is of high technological significance, because this structure type is very suitable for electrodes in many electrochemical devices, such as fuel cells, batteries and sensors [1,2], and in catalysis applications [3]. The template-directed synthesis method is most commonly used for the preparation of such electrodes. This method is based on a deposition of desired materials in interstitial spaces of disposable hard template. When interstitial spaces of template are filled by deposited material, the template is removed by combustion or etching, and then the deposited material with the replica structure of the template is obtained [4, 5]. The most often used hard templates are porous polycarbonate membranes [6, 7], anodic alumina membrane [8-10], colloidal crystals [11, 12], echinoid skeletal stractures [13], and polystyrene spheres [14, 15]. 

For example. Ordered macroporous fibers of either amorphous silica or ordered mesoporous silica MCM-41 were produced using the bacterial superstructure, consisting of a thread of coaligned multicellular filaments of Bacillus subtilis as a biotemplate [37]. Mineralization of wood cellular structures using a surfactant-templated sol-gel solution at different pH values allows for the formation of either positive or negative replicas with a porous hierarchy (Figure 32.3) [44,45,48]. 

---