Formation of copper nanowires by electroless deposition using microtubules as templates

Microtubules (MTs) are self-assembling, protein-based, tubular structures several micrometers long with outer and inner diameters of 25 nm and 15 nm, respectively. This aspect ratio makes MTs ideal templates for producing nanowires for applications such as electrical nano-interconnects. MTs are poorly conductive and their use as interconnects necessitates their metallization. We report a process for metallization of MTs with copper using a biologically benign electroless deposition chemistry consisting of copper sulfate solution containing acetic acid as a complexant and ascorbic acid as reducing agent. The pH of the plating bath is controlled such that copper metallization occurs without disassembling the MTs. Electron microscopic characterization of the morphology and dimensions of the copper nanowires shows that metallization for approximately 1 minute produces a uniform nanowire with an average diameter of approximately 15 nm, suggesting that metallization is initiated selectively from the MT inner core.