Shape evolution of citrate capped gold nanoparticles in seeding approach

Shape evolution of gold nanoparticles in seeding approach in which 25 nm citrate capped gold dots were used as the seeds and the mixtures of tetrachloroauric acid and sodium citrate as the growth solutions was investigated systematically and quantitatively. The citrate capped gold nanoparticles presented shape evolution from dot-shaped to tadpole-like, dumbbell-shaped and rod-like along the reaction. It is identified that the preferential growth along {1 1 0} facet of the face-centered cubic gold seeds related to activity of the gold precursors contributed to the shape evolution from dot-shaped to tadpole-like nanoparticles at the early stage of the reaction. The tadpole-like particles evolved to the dumbbell-shaped ones due to the reduced growth rate and ripening of the gold nanoparticles. Finally, the dumbbell-shaped particles became rod-like in shape attributed to the intraparticle ripening of the gold nanoparticles. This work implies the possibility to control over the shape of the gold nanoparticles in seeding approach in presence of weak ligands such as citrate.