Synthesis and Optical Properties of Homogeneous Nanoshurikens

During the last years the controlled synthesis of Au nanoparticles (NPs) has almost become a reality, and structures such as spheres, cubes, rods, decahedra, or octahedra can be prepared with a la carte dimensions in a very homogeneous manner. However, the fabrication of spiked particles, the most efficient plasmonic NPs, with controllable geometric parameters remains elusive. Here we show how to prepare highly homogeneous spiked nanoparticles composed of a penta-twinned core and five tips. These nanoparticles, reminiscent of ninja nanoshurikens (throwing stars), exhibit the ability to concentrate large electromagnetic fields at the apexes of the tips upon illumination. The apexes also present high affinity for analytes, giving rise to an unprecedented capacity for quantitative optical ultradetection with SERS.