Local Structure of Nanoalloys: From Bimetallic to High-Entropy Alloy Nanoparticles

Abstract

Metal alloy nanoparticles (NPs) have garnered significant interest due to their unique atomic structures and promising applications across various fields. Advancing the rational design of NPs necessitates a detailed understanding of their structural and compositional features. While the complex nature of alloy NPs poses challenges for characterization, X-ray absorption spectroscopy (XAS) offers a powerful, element-specific tool to probe their local structure and electronic properties, furthering the understanding of the structure-property relationship. This work utilizes XAS alongside complementary characterization techniques to investigate three distinct classes of alloy NPs. First, protein-protected AuPd alloy NPs are examined, revealing insights into their elemental distribution, charge transfer dynamics, and evolution of these properties with alloy composition. Second, atomically precise AuAg NPs are analyzed using an XAS-driven approach to construct detailed structural models, determining the identity of specific atomic positions within the NPs. Finally, complex high-entropy alloy NPs are characterized to confirm atomic-level mixing and explore how compositional complexity impacts the local structure. A novel XAS-based methodology is introduced to quantitatively assess local chemical order, providing a versatile tool for the future study of other complex multi-element systems. Collectively, this research deepens the understanding of the structure-property relationships in alloy NPs and highlights the power of XAS in nanoscale material characterization, guiding the future design of NPs for various applications.