Hierarchical Assembly and Oriented Growth of Standing Au Nanodecahedra Superstructures With Sharp Tips and Nanogaps for Boosted Near‐Field Focusing

A persistent challenge in surface‐enhanced Raman scattering (SERS) lies in the precise control of plasmonic superstructure orientation and the construction of nanoscale gaps to maximize near‐field focusing. Here, we report a template‐free hierarchical self‐assembly strategy coupled with oriented growth to fabricate large‐area, highly ordered superstructures of standing Au nanodecahedra (ND). The influence of nanoparticle concentration on the surface tension gradient‐driven assembly process is systematically investigated. Notably, this assembly approach is generalizable to plasmonic nanoparticles with diverse morphologies. Furthermore, the shape evolution, optical properties, and SERS enhancement from Au nanorice to standing Au ND are monitored and elucidated via numerical simulations. The standing Au ND superstructures exhibit a 2.16‐fold higher SERS enhancement compared with their horizontal counterparts, along with uniform signal distribution over large areas. This study not only presents an efficient route for engineering oriented Au ND superstructures with enhanced near‐field focusing capabilities but also highlights the essential role of nanoparticle orientation in tailoring high‐performance SERS properties.