One-pot synthesis of porous gold nanoparticles by preparation of Ag/Au nanoparticles followed by dealloying

Porous gold nanoparticles were obtained from nanoparticle alloys of gold and silver. The alloy nanoparticles were prepared by reducing the gold and silver precursors, HAuCl4 and AgNO3, respectively with NaBH4. The reduction was made in a microemulsion of water-in-oil type and the precursors were contained in the water droplets. The droplet size of the microemulsion was 25–30 nm and the size of the mixed nanoparticles was 5–7 nm. The position of the plasmon band in the absorption spectrum, as well as analysis by energy-dispersive X-ray spectroscopy linked to high resolution scanning transmission electron microscopy showed that the nanoparticles were true alloys, not of core–shell type. The mixed nanoparticles were subsequently dealloyed by treatment with nitric acid, which dissolved silver much more readily than gold.