Liquid Metal Nanoreactor Enables Living Galvanic Replacement Reaction

Galvanic replacement reaction (GRR) holds immense potential for engineering metal nanostructures. This reaction allows for the formation of bimetallic hollow nanostructures in a single step, in which precise control of the reaction is necessary to customize the size, composition, and morphology. Whereas achieving trimetallic or multimetallic systems through sequential GRR is highly desirable, their synthesis remains challenging because of the high complexity of multistep GRR processes and the fact that they require precise control of the addition sequence and amount of metal precursors. Here, we introduce a simplified sequential GRR approach, namely, "living" galvanic replacement reaction (LGRR). The LGRR utilizes a liquid metal (LM) nanoreactor consisting of a chemically active LM core and a polydopamine (PDA) shell. The LM core undergoes stepwise reactions with various dissolved metal ions, leading to the nucleation and growth of reduced metal nanocrystals on the PDA shell within minutes at room temperature. Importantly, the LM core remains active ("living"), and the LGRR continues uninterrupted by both the deposited metals and the addition sequence of the metal precursors. We demonstrate that the LGRR of LM nanoreactors facilitates the stepwise growth of different metal nanocrystals when different metal precursors are added sequentially, resulting in the formation of diverse multimetallic nanostructures that possess a phase-segregated multimetallic shell surrounding an LM core. Furthermore, the LGRR of the LM nanoreactors also enables the rapid synthesis of nanoalloys within 5 min by simultaneously reducing different precursors.