Atom-Precise Metal Nanoclusters

Abstract

A nanocrystal is a crystallite with size greater than about 2 nm. Nanoclusters are non-crystalline nanoparticles that are typically small and composed of a specific number of metal atoms in the core, which are protected by a shell of ligands. Optical properties of large metal nanoparticles in external electromagnetic fields are a function of their size, free-electron density and dielectric function relative that of the surrounding medium. The ultra-small size of nanoclusters allows them to exhibit distinct quantum confinement effects, which in turn results in their discrete electronic structure and molecular-like properties, such as HOMO-LUMO electronic transitions, enhanced photoluminescence, and intrinsic magnetism, to name a few of the characteristics. Metal nanoclusters play an important bridging role between nanochemistry and molecular chemistry. A basic understanding of the structure, electronic and optical properties, as the materials evolve from the atomic state to nanoclusters to fcc-structured nanocrystals, constitutes a major evolution across length scales, and leads to fundamental insights into the correlation between the structure and key characteristics of metal nanoclusters.