Template electrochemical methods

Traditional template synthesis of metal phthalocyanines requires high temperatures to be used. In contrast, electrochemical template methods allow the highly efficient assembly of phthalocyanine-metal complexes in organic solvents under ambient conditions. 

Conductive polymeric nanostructures can be prepared by using hard or soft templates or with template-free methods. The template method has been extensively used because of its simplicity, versatility and controllability. Some further features on this topic are reported in Section 1.3. A typical hard template material can be a thin porous film of aluminum oxide or polycarbonate and polymeric materials ean be deposited into the pores to form nanotubes or nanowires. The electrochemical template method enables a better control of the dimensions compared with the chemical methods. In addition, the nanostructures produced by the electrochemical method are in solid contact with a base electrode that is beneficial for further processing steps when building an electrochemical device. 

The electrophoretic sol-gel template method could overcome the pore size limitation to certain extent (down to a few tens of nanometers), but it is still limited by the size of the sol particles which were preformed prior to being subjected to the electric field. To address this problem, Miao et al. (2002) reported an electrochemical sol-gel template method in which the sol particles were generated within the pores of the AAO template membrane, as shown in Fig. 18.10. 

There exist a variety of methods to synthesize quasi-one-dimensional nanostructured materials, which include but not limited to vapor phase growth, template-assisted synthesis, sol-gel deposition, surfactant-assisted growth, sonochemical method, hydrothermal method, and electrochemical deposition [21], Among the various methods, the electrochemical anodization method is one of the simplest and cheapest methods to synthesize ordered quasi-one-dimensional nanostructure. 

Klein JD, Herrick RD, Palmer D, Sailor MJ, Brumhk CJ, Martin CR (1993) Electrochemical fabrication of cadmium chalcogenide microdiode arrays. Chem Mater 5 902-904 Sima M, Enculescu I, Visan T (2004) The electrodeposition of semiconductor nanowires with thermoelectric properties using template method. Revista De Chimie 55 743-746... 

There are many ingenious and sueeessful routes now developed for nanociystalline synthesis some rely on gas phase reactions followed by produet dispersal into solvents [7, 9, 13, 14 and 15]. Others are adaptations of classic colloidal syntheses [16,17,18 and 19]. Electrochemical and related template methods can also be used to form nanostructures, especially those with anisotropic shapes [20, 21,22 and 21]. Rather than outline all of the available methods, this section will focus on two different techniques of nanocrystal synthesis which together demonstrate the general strategies. 

Figure 11.6 SEM images of polypyrrole microcontainers synthesized electrochemical ly using a soap bubble -assisted soft-template method. (Reprinted with permission from Chemical Communications, Electrochemical synthesis of novel polypyrrole microstructures by L. T. Qu and G. Q. Shi, 2003, 2, 206-207. Copyright (2003) Royal Society of Chemistry)...

Fig. 2 Electrochemical polymerization method using alumina (AI2O3) nanoporons template...

Finally, through electrostatic, hydrophobic and van der Waals interactions between polymer and the surfactant, stable straemres are generated, which serve as ideal soft templates, providing monodisperse nanoparticles. Soft template methods incltrde electrochemical reduction, seeding followed by chemical reduction, redox reactions, selective etching etc. 

Soft-template technique offers advantage of scalability [39]. In hard-template method, a porous membrane of inorganic or polymeric material serves as a rigid mold for chemical or electrochemical replication of stracture. This method provides an easy marmer for production of 1-D nanostractures, but with difficulties of scale up. Hard templates such as silica or carbon spheres are also ideal for synthesis of hollow strac-tures (11 Chen et al. 2003). Classical examples where the template enables the control of morphology of a-Fe Oj nanoparticles can be found in literature (Table 1). 

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