Electrodeposition of portable, metal nanowire arrays

Parallel arrays of long (> 500 m), dimensionally uniform nanowires composed of molybdenum, copper, nickel, gold, and palladium were electrodeposited. Nanowires with diameters in the range from 15 nm to 750 nm were obtained by electrodepositing these metals, or metal oxides, selectively at the step edges present on the surface of a highly oriented pyrolytic graphite electrode. Depending on the metal, either of two methods were used to carry out electrochemical step edge decoration (ESED): Nanowires of Ni, Cu or Mo were prepared by electrodepositing nanowires of a conductive metal oxide such as NiO, Cu 2 O, or MoO 2 . Nanowires of the parent metal were then obtained by reducing the metal oxide nanowires in hydrogen at elevated temperature. Nanowires composed of noble metals and some coinage metal can be obtained by direct electrodeposition of the metal at step edges. Direct electrodeposition involved the application of three voltage pulses in succession: An oxidizing "activation" pulse, a large amplitude, reducing "nucleation" pulse, and a small amplitude reducing "growth" pulse. These nanowires arrays were "portable": After embedding the nanowires in a polymer film, arrays of nanowires could be lifted off the graphite surface thereby facilitating the incorporation of these arrays in devices such as sensors.