Fabrication of metallic nanoporous films by dealloying

The objective of this study is to synthesize and characterize different nanoporous structures by chemical etching. The experiments are conducted on three different materials. 6 carat white gold leafs (Au/Ag alloy, 1:3 ratio by weight) are etched by nitric acid to obtain nanoporous gold structures. During etching, the gold materials congregate to form well connected network structure that is freestanding. The nanoporous gold samples have pore sizes from a few nanometers to a few hundred nanometers depending on the etching time. The second one is the 50/50 solder sheets (Pb/Sn alloy) in which tin is etched by sulfuric acid to create nanostructured lead material. The third is Imitation Italian gold leafs (Cu/Zn alloy, 82/18 by wt %) in which zinc is etched by sodium hydroxide solution to produce nanostructured copper materials. These porous materials are analyzed by scanning electron microscopy and energy dispersive x-ray spectroscopy. The authors observe the composition of the porous materials at every stage of chemical dealloying and conduct experiments with different process parameters to obtain various sizes of self-ordered porous structures. The authors have fabricated nanoporous gold films with pore sizes of 10-100 nm, nanostructured lead materials with pore sizes of 100-300 nm, and copper nanostructures with pore sizes of 10-150 nm. The results demonstrate that chemical etching is a simple and effective fabrication technique for nanoporous materials with high surface area and well defined pore morphology. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3032903]