Templating, direct, nanostructure inorganics

Electrochemical polymerization provides a convenient approach to fabricate CNTs/CP nanocomposites [46-53], Using such a strategy, the morphology and properties of the nanocomposites can be controlled by the electropolymerization conditions, such as the applied potential or current density. Ajayan and co-workers have reported the electrochemical oxidation of aniline in H SO on the CNTs electrode to fabricate CNT/PANl composites [46]. Chen et al. fabricated CNT/PPy nanocomposites, the first example of anionic CNTs acting as the dopant of a CP [47]. Their results showed that PPy was xmiformly coated on the surface of individual CNTs by electrolysis at a low apphed potential for a short time, rendering them potential applications in nanoelectronic devices. Another kind of CNTs/CP composite nanostructures, e.g., CNTs as inorganic fillers in CP matrices [54] can be prepared by a template-directed electropolymerization method. (Figure 13.3)... 

This section has discussed a diverse range of self-assembled synthetic macromolecules such as block copolymers and elastm-like polymers for template-directed assembly of different types of inorganic nanoparticles into anisotropic ID nanostructures. In the next section, we introduce a simple and cost-effective approach for directing the assembly of gold nanoparticles into ID structures via self-assembly of a short commercially available surfactant. 

This new family of mesoporous silica and aluminosilicate compounds were obtained by the introduction of supramolecular assemblies. Micellar aggregates, rather than molecular species, were used as structure-directing agents. Then, the growth of inorganic or hybrid networks templated by structured surfactant assemblies permitted the construction of novel types of nanostructured materials in the mesoscopic scale (2-100 nm) [110,113,117],... 

The same procedure was applied to the synthesis of cadmium selenide and zinc sulfide in LLC surfactant phases using C EO surfactants. A relationship between the covalent nature of bonds in the final product and the success of the templating procedure was established on the basis of silver sulfide, copper sulfide, mercury sulfide and lead sulfide not producing the same results. The interaction of the surfactant headgroups with the precipitated mineral and with its precursor ions are necessary for direct templating. This is also confirmed by the fact that salts that bind precursor ions prevent the formation of an ordered inorganic nanostructure within the LLC phase [51]. 

Block copolymers can be employed as templates to direct the deposition of inorganic nanostructures. Parket al. [82] used an Os04-stained microphase-separated thin film of poly(styrene-foZock-butadiene) that produced holes upon RIE in silicon nitride substrates. The etch ratio between the two phases, stained butadiene and styrene, was only about 1 2. MoUer et aL discussed the use of poly(styrene-fc/ock-2-vinylpyridine), to prepare masks for nanolithography by loading the PVP domains with gold particles [83] or by selective growth of Ti on top of the PS domains [84]. 

Supramoleciflar directed self-assembly of inorganic and inorganic-organic hybrid nanostructures has emerged as an active area of recent research. The recent advance shows a remarkable feasibihty to mimic natoal mineralization systems by a designed artificial organic template, where a supramolecular functional polymer can be directly employed as minerahzation template for the synthesis of novel inorganic nanoarchitectures [165] such as CdS helices [166] and hydroxyapatite (HAP) nanofibers [167]. 

H. Zhou et al. [6] developed a novel bacteria-templated sonochemical route for the controllable assembly of ZnS nanoparticles into desired hollow nanostructures. It is based on artificial mineralization and cell disruption under ultrasound. Two shapes of bacteria cocci and bacillus were used as templates to direct the formation of corresponding ZnS hollow spheres and hollow nanotubes, respectively. The inorganic replicas retain the original morphologies of the templates faithfully. This bacteria-templated sonochemical method can be extended to the synthesis of various ZnS hollow assemblies by templating other shapes of bacterium such as vibrios, spirillum, square bacteria, etc. Meanwhile, this method is expected to be a generic means to the siiiple synthesis of hollow assemblies of various materials. 

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