Studying the Synthesis of Silver Nanocubes and Their Structural Evolution under Controlled Galvanic Reactions.

Galvanic replacement reaction (GRR) with or without a reducing agent is the most commonly used strategy to transform Ag nanocubes (AgNCs) into nanocages, and under this approach, some limited control over the nanocages' morphology and composition has been previously demonstrated. However, there is a lack of systematic study of GRR using other factors beyond a reducing agent to finely tailor the morphology and composition (mono- or bimetallic) of the nanocage formation. In addition, most previous work synthesizes AgNCs using the polyol process method, which has a number of drawbacks. In this work, we synthesized the AgNCs using the gold seed-mediated method and found that their morphology and yield were significantly impacted by both the ratio of silver ions to gold seed volume as well as the concentration of the CTAC surfactant. A detailed study was then carried out on transforming the synthesized AgNCs to nanocages under GRR while manipulating synthesis inputs, including the use of a reducing agent, adjusting the injection rate, and increasing the reaction temperature. Compared to a traditional GRR synthesis, manipulating these different inputs can result in a dramatically different structural evolution for the nanocages, which will impact their optical properties. This understanding allows for the morphology and composition of the nanocages to be effectively manipulated. We propose a plausible mechanism for the observed differing structural evolution of the nanocages under different GRR conditions, which is supported by evidence from further experiments.