Templating method membrane

We chose to use a sacrificial template method to make our nanorods. This method uses a membrane with nano/microscopic sized channels as a mold for the design of a nanowire, fiber, or rod, depending upon the intended use for the object and the materials comprising it. ... 

Membrane templating is capable of producing a range of structures in various sizes. However, the degree of control is not at the molecular scale. An alternative templating method that has molecular-level control over the pore size and the ability to produce ordered arrays of pores is lyotropic liquid crystal templates [53]. Lyotropic liquid crystals are surfactant phases produced at high percentages of surfactant to solvent. 

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. 

The template method is a general approach for preparing nanomaterials that entaU synthesis or deposition of the desired material within the cylindrical and monodisperse pores of a nanopore membrane or other solid [20-22]. Cylindrical nano-strucmres with monodisperse diameters and lengths are obtained, and depending on the membrane and synthetic method used, these may be solid nano wires or hollow nanombes. This method has been used to prepare nano wires and nanombes composed... 

Kang, M. and Martin, C.R. Investigations of potential-dependent fluxes of ionic permeates in gold nanotubule membranes prepared via the template method. Langmuir 17, 2753-2759, 2001. 

The template method for synthesizing nanostructures involves the synthesis of the desired material within the pores of a nanoporous membrane or other solid. This approach has been used in several experiments [224—229] for the preparation of Ti02 nanotubes and nanorods typically, porous aluminum oxide (PAO) nano-templates were used. 

Three-dimensionally ordered macroporous ceramic with high LR ion conductivity was prepared by colloidal crystal templating method using monodispersed polystyrene beads [12]. Monodispersed polystyrene beads with 3 pm diameter were dispersed in water and then filtrated by using a membrane filter under a small pressure difference. After this treatment, polystyrene beads were accumulated on the membrane filter with closed pack structure, as shown in Fig. 4.2. Then, the membrane consisting of accumulated polystyrene beads was removed from the membrane filter and put on a glass substrate. After drying at room temperature, the... 

Nanoporous Hard-Template Methods PANI-NTs have been prepared by the chemical oxidative polymerization of aniline within the pores of PC nanoporous membranes... 

Figure 11.10 A schematic representation of the hard-template method used to prepare CPCs (a) porous membrane, (b) colloidal particles, (c) nanowires...

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). 

The advantage of template synthesis is that the length and diameter of the polymer fibers and tubes can be controlled by the selected porous membrane which results in more regular nanostructures. The template method has been used to synthesize nanofibers and tubes of PPy [19,20], PANI, poly(3,4-ethylenedioxythiophene) (PEDOT) [21], and some other polymers. The general feature of conventional template method is that the membrane should be soluble to be removed after the synthesis in order to obtain single fibers or tubes. It restricts practical application of this method and gives rise to a search... 

In general, template method is classified by soft and hard templates. Whereas anodic aluminum oxide (AAO) membrane, track-etched polycarbonate (PC) and zeolite can be used as hard templates, soft templates include surfactant, cyclodextrin, liquid crystal, etc. Compared with soft and hard templates, template-free method represents the fabrication technique of conducting polymer nanomaterials without the template, which is discussed in this section [115]. 

Hard template method has been used for the 1-D nanostructures such as nanotubes, nanorods and nanofibers of conducting polymers. The commonly used templates are AAO membrane, and track-etched PC membrane, whose pore size ranges from 10 nm to 100 pm. Hard template methods for synthesizing conducting polymer nanomaterials have been extensively reviewed in recent years [156-160]. 

Most template methods can be accomplished by simply immersing the hard template into a monomer/oxidant solution. Recently, Jang et al. produced PPy nanotube and carbon nanotube (CNT) using vapor deposition polymerization (VDP) mediated AAO membrane method [172]. An experimental scheme of this method is represented by Scheme 6. 

In general, PPy nanotubes have been mainly produced by the hard template method [165,172,225,226,247,248]. For example, PPy nanotube with highly imiform surface and controlled waU thickness was fabricated by one-step VDP using AAO membrane [172]. A template-mediated VDP was foimd to be a facile and effective method to fabricate polymer nanotubes. The vapor phase polymerization provides highly uniform tubular walls as well as easy control over the waU thickness. 

Among the several fabrication methods, hard template method, which was pioneered by Martin et al., has been the most famous route of nanotubes and nanowires. Nanotubes of conducting polymers could be readily prepared by filling the nanopores with polymer or polymer solution using AAO template or track-etched PC membrane. PPV nanotube and nanorod had been fabricated in the pores of alumina or PC filters with pore diameter 10-200 nm by... 

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