Templated Synthesisof Mono- and Bimetallic NanogapDimer Arrays

This work demonstrates a templated synthesis of mono- and bimetallic nanoparticle dimers starting from patterned Au nanoparticle seeds. Growth rates of the shell layers and the interparticle distances were adjusted by varying the solution pH and reaction time. Using metal ion sources in aqueous solutions and controlling reduction kinetics, we prepared Au@shell (Au, Ag, Pd, and Pt) nanoparticle dimers with sub-10 nm gap widths. Au@Ag dimers exhibited an order-of-magnitude higher surface-enhanced Raman spectroscopy signal compared to Au@Au dimers with similar gap separations. The generation of Au@Pd and Au@Pt nanoparticle dimers enabled concurrent surface catalysis and SERS to observe the Suzuki–Miyaura reaction and a nitroaromatic reduction reaction, respectively. This templated synthesis method offers precise control of nanogap width and surface properties, providing a versatile platform for plasmon-based catalysis and molecular sensing.