Template-assisted nanostructuring

Next, the template-assisted nanostructured deposition of NiO was tried, following the experimental method of Sonavane et al. for the electrodeposition of nontemplated coatings [62]. For this purpose a 0.5M aqueous NiCl bath containing 0.1 M KCl was prepared, which was complexed using EDTA and pH-adjusted to 8 by addition of KOH. Electrodeposition was conducted in a three-electrode cell at a potential of -1.1 V versus Ag/AgCl for lOOmin. The obtained DG-structure NiO film of about 1 ttm thickness is presented in Fig. 5.5. This preparation technique has two major disadvantages firstly, the very slow deposition rate, and secondly, the transparency of the deposit complicates the anyway difficult preparation route. In Chap. 6, a more elegant approach for nanostructured NiO deposition is presented that overcomes these issues. 

The most exciting challenge is probably the preparation of BN nanostructures, including nanofibers and nanotubules, using the template-assisted PDCs route. Such an approach could allow us to control the morphology and size of the nanostructured BN materials to be incorporated into the BN matrix. This should significantly enhance the mechanical performance of the resulting composites compared to composites reinforced by BN microfibers. 

The variety of porous solid materials that can be used as templates for nanostructure synthesis has been reviewed by Ozin (1992). In the template-assisted synthesis of nanowires, the pores or voids of the template are filled with the chosen material using a number of approaches. Nanowires have been derived via pressure injection, electrochemical deposition, and vapor deposition, as described in the following sections. 

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. 

Yin JS, Wang ZL (1999) Template-assisted self-assembly and cobalt doping of ordered mesoporous titania nanostructures. Adv Mater 11 469... 

There are several references reporting on template-assisted approaches for nanofabrication such as Hulteen and Martin. They are regarded as one of the pioneer groups for functional nanowire array fabrication. With the use of a periodic structured template, one-dimensional nanostructures can be prepared thanks to the confinement effect of the porous template. The templates can be prepared easily with anodization. Control of the aspect ratio and the area density of one-dimensional nanostructures can be achieved by changing the diameter and length of the template, and by changing the anodization voltage. 

Three-dimensionally nanostructured transparent conducting ZnO could serve as electrode for several applications such as dye-sensitized solar cells. Thus, the template-assisted nanopatterning of ZnO via electrodeposition was attempted, following the... 

In this chapter we study the overview of the various naturally and artificially prepared self-assembled nanostructures which are currently very important and in demand in biomedical applications, for example, bone tissues, natural laminated composites present in sea shells, peptide chain arrays and their derivatives and cell membranes are naturally self-assembled materials. And Langmuir—Blodgett films, surfactant-directed nonporous materials, and molecularly directed films, composites, nanombes, nanofibrils, nanowires, spherical vesicles, and template-assisted growth are artificially prepared self-assembled nanostructures. Here we discuss in brief the synthesis of those nanostructures which exist in nature and are prepared artificially to fulfill certain requirements (Figure 2.1). 

There are a number of experimental techniques used to fabricate self-assembled nanostructures from ZnO and other materials. These techniques include the following vapor-liquid-solid, metalorganic chemical vapor deposition, template-assisted, chemical reaction, molecular beam epitaxy, and reactive sputtering. In this section we provide a brief overview of these techniques. 

It is worth noting that the boundaries between numerous bottom-up approaches are sometimes ambiguous, so combining multiple approaches to obtain desirable or complex nanostructures is often necessary. For example, the colloidal process is often combined with template-assisted self-assembly to produce hollow nanospheres and other complex structures [42,43]. This versatility of bottom-up approaches opens many opportunities to fabricate a myriad of nanomaterials with extraordinary properties. 

Template-assisted route has evolved as a good technique to achieve nanowires and nanodots and various nanostructures, but it has its own limitations. For a given material... 

A variety of synthetic procedures for the achievement of PPy nanostructures (spheres, rods, tubules, core-shells) are reported in the literature where the concept of self-assembly is mixed with that of template synthesis and composites fabrication, because the methods often show overlapping features. Most of the examples deal with the template assisted procedure and are reported in the subchapter Templates . 

Wire-shaped growth of nanostructured PPy with diameter <10 nm, has been obtained by electropolymerization at naturally occurring step defects and artificially formed pit defects of HOPG, in a template assisted electropolymerization where the size of the nanostmctures could be controlled by limiting the pyrrole polymerization time at anodic potentials [242], Electrochemical polymerization of pyrrole within the confines of anodized alumina templates and subsequent metal nanoparticles immobilization on the surface of polymer pillars has been used to make surfaces that show roughness on two independently controllable levels sub-microscopic roughness from polymer pillar dimensions and nanoscopic roughness from the appropriate size selection of metal NPs [243],... 

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