Nickel nanowires

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. 

Our approach utilized the metals gold, platinum, then later gold, platinum, and nickel electroplated in succession because the catalytic decomposition of hydrogen peroxide reaction we tested was most efficiently catalyzed with platinum.After fabrication of the nanowires they were freed by removing the conductive silver backing with nitric acid and the sacrificial template with a strong base, sodium hydroxide. Then nanorods were washed with deionized water and ultracentrifuged to achieve a neutral pH. 

A. K. Bentley, J. S. Trethewey, A. B. Ellis, and W. C. Crone, Magnetic manipulation of copper-tin nanowires capped with nickel ends. Nano Lett. 4(3), 487-490 (2004). 

Figure 1.34 Experimental setup showingthe nickel nanowires in a (A) horizontal and (B) vertical position depending on the magnetic field orientation. (Reprinted with permission from Ref. [171]. 2006 American Chemical Society.)...

The ability to modulate electrochemical reactivity and effectively switch OFF the reaction was extended further by Wang and coworkers [174] to control, on-demand, the separation and detection processes in microfiuidic devices. In this work, the catalytic nickel nanowires were placed, reoriented and removed on-demand at the exit of the separation channel of the microfiuidic chip, offering unique possibilities for controlling externally, events inside and outside a microchannel. 

Fig. 13 Schematic representation of the orientation-dependent elastic torque on a nickel nanowire with longitudinal anchoring in 5CB (a) in equilibrium, and (b) in the presence of a magnetic field, (c) Levitation of the nanowire in a twisted nematic cell [446]. (Copyright 2004, American Association for the Advancement of Science)...

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). 

C.4. TEMPLATE SYNTHESIS AND MAGNETIC MANIPULATION OF NICKEL NANOWIRES... 

C.4. Template Synthesis and Magnetic Manipulation of Nickel Nanowires... 

Nickel-mesoporous silicon structures are of considerable industrial interest for various applications. Anisotropy of magnetic properties of the nickel nanowires inside porous silicon conditioned by their high aspect ratio is applicable for the magnetic store production [1], Moreover, these structures offer much promise for the rectenna (a special type of antenna that is used to directly convert microwave energy into DC electricity) fabrication. So, it is of value to study in detail the process of the nickel electrodeposition into pores of porous silicon and elaborate control methods for pore filling with metal. 

Among other reports, the DNA-templated Cu nanowire fabrication by electroless metallization100 or biotemplate synthesis of 3-nm nickel and cobalt nanowires, which may find reality in biomedical applications,101 should be mentioned. 

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