Using template-based electrodeposition nanowires of different diameters, lengths, and materials can be made. We have recently explored new degrees of freedom of nanowires: porosity and surface morphology. We have succeeded in fabricating nanoporous gold (NPG) nanowires with high surface area and well-defined pore morphology.

We first make single-phase two-component alloys (e.g., Au18Ag82) nanowires using template-based techniques and electrodeposition. The nanowires are then removed from the templates. When the single-phase alloy nanowire is etched in a suitable solution, a nanoporous layer of one component (e.g., Au) can be formed due to the preferentially dissolution of the other component (e.g., Ag). As a result, NPG nanowires with ligament size of 35-50 nm and pore sizes of 10-40 nm can be made, as shown above. The pore sizes and morphology depend on the alloy compositions, as can be seen by comparing the two NPG nanowires starting with alloys of different Au content. We have also succeeded in fabricating multi-segment nanowires that contain segments of NPG, for example, Pt/NPG/Pt and Au/NPG, as shown below.

We are currently exploring applications that take advantage of the high surface area and unusual morphology of these novel structures.

PUBLICATIONS:

C. Ji and P. C. Searson, "Fabrication of Nanoporous Gold Nanowires," Appl. Phys. Lett. 81, 4437 (2002).

C. Ji, G. Oskam, Y. Ding, J. D. Erlebacher, A. J. Wagner, and P. C. Searson "Deposition of Au_xAg_(1-x)/Au_yAg_(1-y) Multilayers and Multisegment Nanowires," J. Electrochem. Soc., (in press).