Seedless and templateless synthesis of rectangular palladium nanoparticles

Highly crystalline rectangular palladium nanoparticles have been successfully synthesized via the reduction of K₂PdCl₄ by ascorbic acid in the presence of a surfactant, cetyltrimethylammonium bromide, under room temperature and trisodium citrate is a key factor for high yield of nanocubes and nanorods. The average length and aspect ratio of the nanorods can be tuned by varying the concentration of trisodium citrate. These rectangular nanoparticles were stable for months as colloids. However, after exposure to air for about 100 days, the dry nanoparticles on TEM grids were oxidized to form shells of 1.6-3.8 nm thick covering the nanoparticle surfaces.