Silver exchange dynamics in monolayer-protected doped gold clusters

The mechanism of inter-cluster exchange reactions remains an open problem in nanoparticle chemistry. Such reactions, first reported in 2015, involve the exchange of metal atoms between ligand-protected nanoparticles in solution and have enabled the synthesis of heterometallic clusters with precise dopant counts. While previous computational studies have proposed plausible exchange pathways, none have explicitly captured the dynamics of a cluster-cluster collision. Here, we use a direct dynamics approach combined with quantum-based semiempirical potentials to simulate collisions between silver-doped and undoped gold nanoparticles and to follow atom exchange events in real time. The simulations reveal that restructuring at the core-monolayer interface is a key initiating step, enabling exposure of core metal atoms. Subsequent transfer of silver between clusters is mediated by thiolate ligands, which stabilize the migrating atom through successive metal-sulfur interactions across the inter-cluster region. Beyond elucidating the exchange mechanism, this work demonstrates a general strategy for modeling reactive collisions and large-scale dynamical processes in nanomaterials.