Highly Symmetric Gold Nanostars: Crystallographic Control and Surface-Enhanced Raman Scattering Property.

Gold nanostars have attracted widespread interest due to their remarkable properties and broad applications in plasmonics, spectroscopy, biomedicine, and energy conversion. However, current synthetic methods of Au nanostars have limited control over their symmetry; most existing nanostars are characterized by having uncertain number of arms with different lengths and random spatial arrangement. This morphological arbitrariness not only hampers the fundamental understanding of the properties of Au nanostars, but also lead to poor reproducibility in their applications. Here we demonstrate that, by using a robust solution-phase method, Au nanostars with unpreceded degree of symmetry control can be obtained in high yield and with remarkable monodispersity. Icosahedral seeds are used to dictate the growth of 3D evenly distributed arms in an Ih symmetric manner. Alkylamines serve as shape-control agent to regulate the growth of the hexagonal pyramidal arms enclosed by high-index facets. Benefiting from their high symmetry, the Au nanostars exhibit superior single-particle SERS performance compared to asymmetric Au nanostars, in terms of both intensity and reproducibility.