Nanowires electrochemical deposition

Figure 20 Schematic diagram of a nanoporous BCP template prepared from athickfilm of PS-A-PMMA oriented with an electric field. The PMMA was removed leaving a template. Subsequent electrochemical deposition generated nanowires in a cross-linked PS matrix. On the right is a scanning electron microscopy image of cobalt nanowires electrochemically deposited in the cross-linked PS template.

Xu D, Chen D, Xu Y, Shi X, Guo G, Gui L, Tang Y (2000) Preparation of II-VI group semiconductor nanowire arrays by dc electrochemical deposition in porous aluminum oxide templates. Pure Appl Chem 72 127-135... 

Porous aluminum oxide can be used as a template for the production of nanowires and nanotubes. For example, metals can be deposited on the pore walls by the following procedures deposition from the gas phase, precipitation from solution by electrochemical reduction or with chemical reducing agents, or by pyrolysis of substances that have previously been introduced into the pores. Wires are obtained when the pore diameters are 25 nm, and tubes from larger pores the walls of the tubes can be as thin as 3 nm. For example, nanowires and nanotubes of nickel, cobalt, copper or silver can be made by electrochemical deposition. Finally, the aluminum oxide template can be removed by dissolution with a base. 

Goldys EM, Drozdowicz-Tomsia K, Xie F, Shtoyko T, Matveeva E, Gryczynski I, Gryczynski Z (2007) Fluorescence amplification by electrochemically deposited silver nanowires with fractal architecture. J Am Chem Soc 129 12117-12122... 

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. 

Electrochemical deposition has attracted increasing attention as a technique for nanowire fabrication. Traditionally, electrochemistry has been used to grow thin films on conducting surfaces. Because electrochemical... 

Figure 19(a) shows the temperature dependence of resistance R(T) for bismuth nanowire arrays (dw = 7 - 200 nm) synthesized by vapor deposition and measured by Heremans et al. (2000). Hong et al. (1999) reported similar resistance measurements on bismuth wires of larger diameters (200 nm to 2, uni) prepared by electrochemical deposition (Fig. 19(b)). These two studies... 

R(T) is predicted to display a monotonic temperature dependence at a high defect level. This is illustrated by the dashed curve in Fig. 19(c) for polycrystalline 70-nm bismuth wires. Because the nanowires prepared by electrochemical deposition were found to be polycrystalline, their carriers would experience more boundary scattering, resulting in the monotonic R(T) behavior noted experimentally in Fig. 19(b). 

Sun, L., Searson, P. C., and Chien, C. L., Electrochemical deposition of nickel nanowire arrays in single-crystal mica films. Appl. Phys. Lett. 74,2803 (1999a). 

Electrochemical deposition advantage, 179 choosing template, 178 contrast to pressure injection, 178-179 nanowire fabrication, 177-179... 

Recently, Sun et al. [60] proposed to fabricate Ag nanostructures by electrochemical deposition of Ag in anodic aluminum oxide templates with each pore diameter of 100 nm. The morphology of Ag substrates was characterized by EESEM. The length of the Ag nanowires is estimated to be about 2 pm from the EESEM images. In addition, the SERS enhancement factor calculated for Ag nano wires SERS substrates is approximately 10 in magnitude. The Ag nano wire arrays are expected to have important applications in the development of high sensitivity SERS-based substrates. 

Biotemplates have been fabricated from two-dimensional crystalline surface proteins for the subsequent electrochemical deposition of nanowire structures [82]. These surface layer proteins encapsulate certain bacterial cells, controlling extracellular transport. They form especially robust thin films over cells, and are resistant to conditions that normally denature proteins, such as low pH and heat, thus making them ideal as template materials for electrodeposition. Schwartz and coworkers investigated a hexagonally packed intermediate surface layer protein from... 

Li CZ, Tao NJ (1998) Quantum transport in metallic nanowires fabricated by electrochemical deposition/dissolution. Appl Phys Lett 72 894-896... 

Aligned polymer nanowire structures have been developed using an electrochemical deposition technique to form aligned PAn arrays on smooth and textured electrode substrates without the need for a porous templating structure.248 249 Ori-... 

In this work, ac electrochemical deposition has been applied to nanowire formation in PAA. The advantage of the ac electrochemical deposition is that the membrane remains on the A1 substrate and that the barrier layer does not avoid the deposition. In this case, the fabrication of ordered and metal-filled porous alumina structures is not limited by the thickness and size of the PAA layer. These structures may be used in high temperature technological operations. 

The electrochemical deposition is carried out through the pores on the metallic layer that coated the back side of the template and is used as a cathode for the electroplating. The micro- and nanomaterials that are produced in this way take the form of wires and tubules. After finishing of the deposition process, the polymer membrane is dissolved in the corresponding solvent, for example, in alkali solution at temperature 70°C-80°C for PET film or in dichloromethane for the PC membrane. The scheme of the ion-track membrane production in thin polymer film and electroplating of copper nanowires within the pores is given in Figure 18.1. 

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