Understanding galvanic replacement reactions : the case of Pt and Ag

Synthesis of nanocrystals (NCs), where material science elements are addressed with organic chemistry precision techniques, is especially challenging and difficult to control. This difficulty arises from the increased complexity of the mineralization processes and the generation of a liquid-solid interface. These aspects, along with a strong susceptibility to reaction kinetics, ultimately translate into serious challenges for reproducibility and morphological control. By systematically varying the different parameters used to control the morphology of NCs, including complexing agents, coreducers, and cooxidants, the general reaction landscape can be mapped and the most stable and reproducible recipes can be identified. We apply this concept to the model transmetallation reaction between immiscible Pt and Ag forming hollow Pt NCs by galvanic replacement reactions. In this work, 648 synthetic recipes were performed and characterized per duplicate, from which a subset of 307 recipes leading to the controlled formation of hollow NCs were further analyzed to correlate reaction conditions with the final obtained structure and stability (reproducibility). As a result, we present robust general synthetic protocols leading to the ad hoc production of Pt-based hollow NCs with independent control of shell thickness, void size, surface roughness, and degree of porosity.