Kinetically Controlled Synthesis of Concave Five-Fold Twinned Gold Nanocrystals and Their Surface-Enhanced Raman Scattering Properties.

The controllable synthesis of plasmonic metal nanocrystals with well-defined shapes is of great significance for their potential applications, and it requires a good understanding of the mechanism under thermodynamically and kinetically controlled reactions. Herein we present a seed-mediated growth approach to a series of five-fold twinned (FT) gold nanocrystals. Specifically, concave FT Au nanocrystals with embedded grooves at the twin boundaries are preferentially prepared under kinetically dominated conditions. Meanwhile, pentagonal bifrustums, truncated pentagonal bifrustums, truncated decahedrons, and decahedrons with high purity can be obtained by tailoring the deposition process. Therefore, reversible evolution between gold decahedrons and concave nanostructures was achieved by tuning the deposition modes. Importantly, concave FT Au nanocrystals display excellent surface-enhanced Raman scattering activities for 4-aminothiophenol due to their unique morphological characteristics. Our work provides an avenue for rational synthesis of FT gold nanostructures with tunable shapes and will promote their potential applications in plasmonics and catalysis.