Size- and Composition-Controlled High-Entropy Alloy Nanocrystals via Colloidal Synthesis

High-entropy alloy nanocrystals (HEA NCs) are an emerging family of materials that feature the substitutional mixing of at least five elements. They are promising for various applications, including catalysis and batteries. Yet, their composition-structure-performance relationships are poorly understood. Therefore, there is a need for synthetic methods that allow control of HEA NCs. Here, we demonstrate a facile colloidal chemistry approach to synthesize size- and composition-controlled HEA NCs of transition metals in a one-step reaction. We show that both the morphology and crystal structure of the HEA NCs are influenced by the individual metals of which they are composed. HEA NCs primarily composed of noble metals form wavy nanowires, whereas non-noble metals result in spherical-shaped HEA NCs. In addition, we find that HEA NCs composed of metals that crystallize in different structures (e.g., fcc and hcp) are defect-rich, with different polymorphs forming at different synthesis temperatures. We expand the range of achievable compositions to also include post-transition metals (Ga, In, Zn, and Sn) using HEA NCs as seeds in an amalgamation reaction. Taken together, we achieve the synthesis of HEA NCs using colloidal chemistry with unprecedented tunability of their structural characteristics, including their size, composition, morphology, and crystallography.