Morphology-Directed Assembly and Chiroptical Properties of Chiral Gold Nanorods

Abstract Chiral plasmonic nanostructures with high optical asymmetry factors (g-factors) are promising for chiral recognition, biosensing, and asymmetric catalysis. However, the relationships among building-block morphology, assembly geometry, and chiroptical response remain incompletely understood. Here, we regulate the assembly structure and g-factor by controlling the morphology of chiral gold nanorods (c-GNRs). c-GNRs with different aspect ratios and degrees of surface twisting were prepared by sequential regrowth and thermal aging, respectively, and then assembled into structurally self-matched side-by-side configurations. Systematic analysis showed that moderate aspect ratios and surface twisting improved geometric matching and interlocking between adjacent c-GNRs. The resulting decrease in interparticle gap strengthened plasmonic coupling and increased the magnitude of the assembly g-factor to 0.22. Finite-difference time-domain simulations supported the experimentally observed dependence of the chiroptical response on morphology and interparticle spacing. These results show that optimizing geometric matching and coupling distance, rather than simply increasing nanoparticle size or surface twisting, is an effective strategy for enhancing the optical asymmetry of chiral nanoparticle assemblies.