Gold Nanostructures Produced on Several Types of Metals by Low-temperature Heating of Dry Residues of a Solution of HAuCl<sub>4</sub> in Air

In the present study, low-temperature heating of the dry residue of a 10 µL droplet of an HAuCl4 solution on a substrate and a metallic foil facing the dry residue was performed for 20 min in air in order to produce gold nanostructures on the metallic foil. When a titanium foil and a stainless steel (SUS316L) foil were used as metallic foils, dispersed gold nanoparticles were produced on these foils. On the other hand, in the case that a silver foil was used, microscopic objects having nanostructures, which would contain metallic gold, were densely formed on the silver foil.