Synthesis and Optical Properties of Gold Nanodecahedra with Size Control

Regular gold nanodecahedra (pentagonal bipyramids) are obtained in high yield through ultrasound‐induced reduction of HAuCl4 by dimethylformamide on presynthesized seeds (see figure). A dependence of the final morphology on the crystalline structure of the seeds is demonstrated by growing gold on single‐crystal platinum nanoparticles, which yields uniform octahedra. Resolution of Maxwell's equations for bicones shows good agreement with experimental optical properties.