Facile Synthesis of High-Entropy Alloy Nanoparticles Comprising of Dissimilar Elements.

High-entropy alloy nanoparticles (HEA-NPs) have developed as desirable functional material. Methods including the direct solution synthesis have been reported, and it has demonstrated success in fabricating HEA-NPs. Nevertheless, its applicability to systems containing dissimilar elements remains constrained by phase segregation and incomplete alloying. Thus far, the facile synthesis of HEA-NPs composed of dissimilar elements is extremely challenging due to their vast difference in physiochemical properties. Herein, we propose an innovative two-NP conversion pathway to synthesize complex metallic NPs and achieved colloidal AgCuPtNiGaAuCo HEA-NPs in the solution phase, which include multiple immiscible metals. Electron microscopy characterization demonstrates that the product NPs are monodisperse and uniform. Energy-dispersive spectroscopy elemental mapping confirms the presence of various metal elements in each NP and reveals the spatial distribution of the elements. We demonstrate that these elements are combined through atomic diffusion between two distinct precursor NPs, which is motivated by the differential affinity among the constituent metals. The atomic diffusion process was also readily observed thanks to such a solution phase method that enables the combination of precursor NPs to be monitored. All of these results also suggest that some precursor NPs act as a template in the atom diffusion process. Moreover, we identify the critical role of liquid metal Ga in the uniform alloy formation and preliminarily discuss the mechanism behind. This work potentially provides a good chance for property tuning and material discovery of functional HEA-NPs.