Templates nanostructures

Following the introduction of MCM-41 type materials [1], the synthesis of surfactant templated nanostructured materials has attracted the attention of the scientific community because it provides the possibility of tailoring pore size, geometry and surface chemistry through control of the synthesis conditions. Potential applications of these materials range from separations and catalysis [2] to the production of biomimetic materials [3] and devices for optical and electronic applications [4]. Several synthesis protocols have been developed in the last ten years and are the focus of many recent reviews [5]. Despite the enormous experimental effort to develop methods to control the structure and composition of templated nanoporous materials, modeling the different processes has remained elusive, mainly due to the overlapping kinetic and thermodynamic effects. The characterization of... 

Non-templated nanostructured materials e. g. Metal-organic frameworks (MOF), self-assembled block polymers... 

Bantz, K.C. and Haynes, C.L. (2008) Surface-enhanced Raman scattering substrates fabricated using electroless plating on polymer-templated nanostructures. Langmuir, 24,... 

Km-lann SD, Riley AE, Kirsch BL, et aL (2005) Chemical tuning of the electronic properties in a periodic mrfactant-templated nanostructured semiconductor. J Am Chem Soc 127 12516-12527... 

Different behaviors and sometimes controversial results have been reported for membrane-templated nanostructures of PEDOT, showing room-temperature conductivity from roughly 60 S cm to 550 S cm and a prevalently two-dimensional VRHM transport at very small diameters (35 nm). This behavior can be rationalized by considering a heterogeneous internal structure in the wires, with an external, more conductive shell, which is likely related to a higher conformational order of the polymer chains near the walls... 

Blake, S., Limin, L, Vijay,)., Chad, T., Schwartz, D., McPherson, G., Bose, A. and Agarwal, V. (2003) Templating nanostructure through the self-assembly of surfactants, in Synthesis, Functionalization and Surface Treatment of Nanoparticles, American Scientific Publishers, Stevenson Ranch, California, pp. 51-65. 

In addition to chemical or physical properties, a fascinating aspect of fullerene related materials is their central empty space, where atoms, molecules or particles can be enclosed. The enclosed particles are then protected by the robust graphitic layers from chemical or mechanical effects. The very long cavities of CNTs have a special potential due to their high aspect ratio and they can be used as templates to fabricate elongated nanostructures. 

Streptavidin-single-stranded DNA covalent conjugates were described as the building blocks for assembling nanostructured scaffolds [31], The amount and type of biotinylated ligands were used to modulate the affinity of duplex formation between solid-phase-bound nucleic acid templates and DNA-streptavidin conjugates. This system has been proposed for the design of fine-tuned sequence detection systems. 

The formation of nanostructures such as nanodot arrays has drawn a great attention due to the feasible applications in a variety of functional structures and nanodevices containing optoelectronic device, information storage, and sensing media [1-3]. The various methods such as self-assembled nanodots from solution onto substrate, strain-induced growth, and template-based methods have been proposed for the fabrication of nanodot arrays on a large area, [4-6]. However, most of these works can be applied to the small scale systems due to the limited material systems. 

Within the scope of thermoelectric nanostructures, Sima et al. [161] prepared nanorod (fibril) and microtube (tubule) arrays of PbSei. , Tej by potentiostatic electrodeposition from nitric acid solutions of Pb(N03)2, H2Se03, and Te02, using a 30 fim thick polycarbonate track-etch membrane, with pores 100-2,000 nm in diameter, as template (Cu supported). After electrodeposition the polymer membrane was dissolved in CH2CI2. Solid rods were obtained in membranes with small pores, and hollow tubes in those with large pores. The formation of microtubes rather than nanorods in the larger pores was attributed to the higher deposition current. 

Figure 19 illustrates key steps of the FI2O2 formation at the nanostructured catalyst surface. An important feature is the imprintment and maintenance of the (11 0) crystal surface through the polymer template because the specific row of metal atoms favours the formation of hydrogen peroxide while minimizing byproducts such as water. 

Thermodynamic control (Figure 1, right) is based on adsorption of substances until quasi-equilibrium stage. In this case, the surface ratio of the adsorbed species is defined by the ratio of products of their concentration and binding constant. This deposition is much less influenced by poorly controllable fluctuations of external conditions and provides much better reproducibility. The total coverage can be almost 100%. Because of these reasons, the thermodynamic control is advantageous for preparation of mixed nanostructured monolayers for electrochemical applications including a formation of spreader-bar structures for their application as molecular templates for synthesis of nanoparticles. 

Gold electrodes coated by nanostructured self-assembled monolayer of TMPP and Cl2 are used as template for in situ synthesis of metallic nanoparticles (Figure 2). 

Figure 2. Electrochemical template-controlled synthesis of nanoparticles on nanostructured monolayer. The size of nanoparticles depends on the reduction charge and can be adjusted easily. (Reprinted from Ref [18], 2005, with permission from Wiley-VCH.)...

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