Geometry-Controlled Assembly of Self-Standing Nanorods With Undisturbed Plasmonics

The ability to control the spatial organization of nanoscale building blocks into well-defined architectures remains a major challenge in materials science, as collective optical, electronic, magnetic, and catalytic properties often emerge from their precise arrangement. In plasmonic systems, coupling between localized surface plasmon resonances (LSPR) enables nanoscale light manipulation, yet current assembly strategies typically produce disordered architectures that limit practical applications. Here, we report a geometry-controlled assembly approach that directs gold@silver core-shell nanorods into vertically aligned configurations on individual colloidal templates. By exploiting a size-dependent "magic number" effect between nanorods and templates, we precisely control interparticle spacing and orientation, preserving the intrinsic optical response of individual nanorods while enabling collective mesoscale control. This strategy provides a general framework for assembling nanostructures with tunable optical properties, bridging colloidal dispersions and functional solid-state architectures. As a proof of concept, we demonstrate highly reproducible surface-enhanced Raman scattering (SERS) platforms with enhancement factors exceeding 10⁶ and excellent uniformity. Beyond SERS, this approach offers a versatile route for engineering plasmonic and hybrid materials for photonics, sensing, and nanoscale energy conversion, where geometry-driven interactions determine functional performance.