Plasmon-Mediated Synthesis of Hybrid Silver–Platinum Nanostructures

Fine-tuning of metal ion reduction kinetics is crucial to the successful synthesis of designer bimetallic nanomaterials with well-defined morphologies and tailored localization of the constituent elements for use in catalysis, sensing, and other applications. However, achieving desired reduction kinetics can be challenging within the restrictions of available reducing agents, seed particle stability, metal ion solubility, and competing chemical processes such as galvanic exchange. Herein, we report the plasmon-assisted reduction of Pt ions onto Ag cores by using visible light illumination to accelerate the oxidation kinetics of a weak reducing agent, trisodium citrate. Using this approach, we are able to synthesize both core–shell and core–satellite structures composed of a plasmonic Ag core and a poorly plasmonic Pt shell or satellites. The controlled formation of these hybrid structures relies on the plasmon-mediated enhancement of the Pt ion reduction rate into a range where, under standard thermal conditions, reduction with citrate is too slow and reduction using even low concentrations of a slightly stronger reducing agent is too fast. This work expands the scope of citrate-assisted plasmon-mediated synthesis to metals other than Ag, opening possibilities for using plasmon-enhanced reduction by citrate as a more generalizable synthetic tool.