Photochemically Controlled Synthesis of Anisotropic Au Nanostructures : Platelet-like Au Nanorods and Six-Star Au Nanoparticles

We report the shape-controlled synthesis of anisotropic Au nanostructures through TiO₂-assisted photochemical reduction of HAuCl₄. By using this method, we have successfully synthesized the platelet-like Au nanorods and six-star Au nanoparticles. Importantly, the platelet Au nanorod exhibits the unique asymmetric five-twinned structure. The colloidal TiO₂ sols were used as both the photocatalyst to initiate the reaction and the stabilizing agent for the produced Au nanostructures. Significantly, in this photochemical process, the tunable irradiation intensity allows us to kinetically control the crystal evolution at various growth stages, leading to the shape difference of ultimate gold nanostructures. Our synthetic method shows a great potential as an alternative or supplement to the other wet chemical approaches for the shape-control of metallic nanostructures. © 2010 American Chemical Society.