Gold nanodumbbell-seeded growth of silver nanobars and nanobipyramids

Gold nanodumbbells (NDs) are prepared by the reduction of gold ions in the presence of gold nanorods. Gold NDs are then employed for the synthesis of gold–silver core–shell nanoparticles (Au@Ag NPs). The quasi-ellipsoidal NPs could be found at room temperature, but Au@Ag bar and triangular bipyramid (TBP) NPs were obtained at 75 °C. Our results show that the long ends of gold NDs are in the position of the bar center and closely paralleled the shorter edge of TBP. Mechanisms in the growth of silver on gold NDs are proposed for the formations of these Au@Ag NPs.