Fabrication of freestanding gold nanotubes

Ag nanowhiskers were grown on a C-coated Si substrate at 800 °C and subsequently coated with Au by physical vapor deposition. The Au forms a single crystalline, epitaxial layer on the nanowhisker and a polycrystalline Au film on the substrate surface. Annealing at 150 °C for 70 h activates diffusion of Ag into the Au grain boundaries of the polycrystalline film, emptying the Ag nanowhisker core. The remaining epitaxial Au film forms the single crystalline wall of Au(Ag) nanotubes.