Lighting up Metal Nanoclusters as Promising Molecular Emitters

Atomically precise metal nanoclusters (NCs) have emerged as promising optical materials in recent years. At the transition size between metal atoms and plasmonic metal nanoparticles, metal NCs exhibit elusive mechanisms underlying their photoluminescence (PL) properties. This fundamental understanding not only requires establishing a correlation with charge carrier dynamics, but can shed light on the design of metal NCs with desired optical properties. This Review discusses the charge carrier dynamics contributing to PL, including excitation, transition, and relaxation, highlighting the critical roles of the structure and active surface of metal NCs. Additionally, metal NCs can serve as building blocks or precursors to tailor PL properties through intermolecular interactions. Finally, we summarize emergent applications and highlight the challenges and opportunities for photoluminescent metal NCs, hoping that this work will stimulate more research on fundamental understanding and applications.