Metallic molybdenum (Mo(o)) wires with diameters ranging from 15 nanometers to 1.0 micrometers and lengths of up to 500 micrometers (0.5 millimeters) were prepared in a two-step procedure. Molybdenum oxide wires were electrodeposited selectively at step edges and then reduced in hydrogen gas at 500 degrees C to yield Mo(o). The hemicylindrical wires prepared by this technique were self-uniform, and the wires prepared in a particular electrodeposition (in batches of 10(5) to 10(7)) were narrowly distributed in diameter. Wires were obtained size selectively because the mean wire diameter was directly proportional to the square root of the electrolysis time. The metal nanowires could be embedded in a polystyrene film and lifted off the graphite electrode surface. The conductivity and mechanical resiliency of individual embedded wires were similar to those of bulk molybdenum.

No abstract

Molybdenum (Mo0) nanowires with diameters ranging from 13 nm to 1 μm and having lengths of up to 500 μm have been synthesized by a two-step process involving the electrodeposition of molybdenum dioxide (MoO2) on a highly oriented pyrolytic graphite (HOPG) surface followed by reduction of the MoO2 nanowires at 500 °C to form molybdenum metal. MoO2 nanowires were electrodeposited reductively from an alkaline MoO4 2- solution using a low overpotential of <|200 mV|. Under these conditions, the nucleation of MoO2 occurred selectively at step edges present on the HOPG surface, and a high linear density (>30 μm-1) of MoO2 nuclei was formed along each step edge on the graphite surface. With continued growth, MoO2 nuclei that were 10−15 nm in diameter coalesced with adjacent nuclei along the step edge to form continuous nanowires having approximately this same diameter. Longer deposition times, t dep, produced smooth MoO2 nanowires with diameters proportional to t dep 1/2. These nanowires had a uniform diameter and a smooth surface, and the nanowire-to-nanowire variation in diameter was 10−30%. In contrast to nanowires of MoO2, which were brittle and subject to breakage, molybdenum metal (Mo0) nanowires were resilient and resistant to breakage. Arrays of Mo0 nanowires could be embedded in a polymer film and lifted off the graphite surface. In humid air (≈55% relative humidity) at room temperature, the resistivity of Mo0 nanowires increased by 10% h-1 as an insulating surface oxide of MoO3 formed.