The fabrication of short metallic nanotubes by templated electrodeposition

Abstract

Template-based electrochemical synthesis has widely been used to produce metal nanowiresand nanorods. Commercially available filtration membranes, such as anodic aluminumoxide (AAO) and polycarbonate track etch membranes, have commonly been utilized ashard templates for this purpose. In this process, a thick metal film is usually sputtered orvacuum evaporated onto one side of the membrane to block the pores and serve as theworking electrode for the subsequent electrodeposition. Here, we show that duringthe deposition of the metal electrode for AAO membranes, the electrode metaldiffuses into the pores and is deposited on the pore walls which leads to preferentialelectrodeposition of metal on the walls and therefore forms metal tubes. Thisphenomenon has been utilized to fabricate short nanotubes by carefully controlling theelectrodeposition conditions. The process is a straightforward method for anyelectroplatable materials to form nanoscale tubular structures. The effects ofworking electrodes and electrodeposition conditions on the formation of tubularstructures are discussed in detail. A new mechanism based on this simple fact isproposed to explain the formation of Ni tubes by Ni–Cu co-deposition. Also, wedemonstrate how to distinguish magnetic nanotubes from nanorods by a simple magneticmeasurement.