Galvanic replacement-free site-specific growth of Au-Islands on Ag nanorods under strong ligand-mediated interfacial energy control

To synthesize hybrid nanostructures, precise structural control holds promise to modulate their physicochemical properties. Interestingly, due to the close physico-chemical nature and Galvanic Replacement (GR) between Au ions and Ag, the fabrication of Ag-Au Janus-like structures by growing Au on Ag free of GR is challenging. In this work, in the growth of Au on AgNR seeds, through employing the Na₃Au(SO₃)₂ complex as precursor to inhibit GR and the MBIA ligand as surface energy tuning agent to induce anisotropic growth, the GR-free growth of Au-Island on AgNR was successfully achieved. More interestingly, GR-free site-specific growth of Au-Islands on the entire surface, both tips, and single tip of AgNRs was also realized by varying the concentration of MBIA or the amount of AA reductant, demonstrating the excellent feasibility in synthetic control. These AgNR–Au Janus-like structures exhibit tunable localized surface plasmon resonance (LSPR) across the UV–Vis-NIR range and strong surface-enhanced Raman scattering (SERS) signals, making them promising candidates for LSPR- and SERS-based applications. Our synergistic ligand-mediated structure control strategy can be extended to other bimetallic systems, thus enabling the construction of sophisticated heterostructures with enhanced or new properties for various applications.